Publications by authors named "Haobo Jiang"

105 Publications

Non-targeted metabolomics of intestinal flora in seborrheic patients based on ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) techniques.

Ann Palliat Med 2021 Apr;10(4):4354-4368

Department of Dermatology, Dongguan Tungwah Hospital, Dongguan, China.

Background: To explore the role of intestinal flora in seborrhea, non-targeted metabolomics analysis was carried out.

Methods: Fecal samples were collected from 5 seborrheic patients and 5 healthy controls from October 2019 to April 2020. Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) was used to detect metabolic fingerprinting in feces samples, and high-throughput sequencing and bioinformatic analysis of 16S rRNA for intestinal flora. The variable importance in projection (VIP) values of orthogonal partial least squares-discriminant analysis (OPLS-DA) and P values of univariate statistical analysis were used to determine the differential metabolites between the seborrhea group and the control group. The interaction between flora and metabolites was analyzed using several approaches.

Results: A total of 45 metabolites with significantly different intensities were found between the seborrhea group and the healthy control group. A positive correlation between flora and metabolites was found in 57 pairs and a negative correlation was found in 104 pairs. In addition, 11 metabolic pathways were significantly altered, including 4 amino acid metabolic pathways, 2 bile acid metabolic pathways, and 2 basic metabolic signaling pathways (ABC transporters pathway and mTOR signaling pathway). Central carbon metabolism in cancer, glutathione metabolism, protein digestion and absorption were also involved.

Conclusions: The occurrence of seborrhea may be related to changes in intestinal flora and metabolic pathways. There is a close association between seborrhea and amino acid metabolic pathways or ABC transporters.
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http://dx.doi.org/10.21037/apm-21-331DOI Listing
April 2021

Changes in composition and levels of hemolymph proteins during metamorphosis of Manduca sexta.

Insect Biochem Mol Biol 2020 12 20;127:103489. Epub 2020 Oct 20.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA. Electronic address:

The tobacco hornworm, Manduca sexta, is a lepidopteran model species widely used to study insect biochemical processes. Some of its larval hemolymph proteins are well studied, and a detailed proteomic analysis of larval plasma proteins became available in 2016, revealing features such as correlation with transcriptome data, formation of immune complexes, and constitution of an immune signaling system in hemolymph. It is unclear how the composition of these proteins may change in other developmental stages. In this paper, we report the proteomes of cell-free hemolymph from prepupae, pupae on day 4 and day 13, and young adults. Of the 1824 proteins identified, 907 have a signal peptide and 410 are related to immunity. Drastic changes in abundance of the storage proteins, lipophorins and vitellogenin, for instance, reflect physiological differences among prepupae, pupae, and adults. Considerably more proteins lacking signal peptide are present in the late pupae, suggesting that plasma contains relatively low concentrations of intracellular components released from remodeling tissues during metamorphosis. The defense proteins detected include 43 serine proteases and 11 serine protease homologs. Some of these proteins are members of the extracellular immune signaling network found in feeding larvae, and others may play additional roles and hence confer new features in the later life stages. In summary, the proteins and their levels revealed in this study, together with their transcriptome data, are expected to stimulate focused explorations of humoral immunity and other physiological systems in wandering larvae, pupae, and adults of M. sexta and shed light upon functional and comparative genomic research in other holometabolous insects.
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http://dx.doi.org/10.1016/j.ibmb.2020.103489DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7704632PMC
December 2020

Hemolymph protease-5 links the melanization and Toll immune pathways in the tobacco hornworm, .

Proc Natl Acad Sci U S A 2020 09 8;117(38):23581-23587. Epub 2020 Sep 8.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078;

Proteolytic activation of phenoloxidase (PO) and the cytokine Spätzle during immune responses of insects is mediated by a network of hemolymph serine proteases (HPs) and noncatalytic serine protease homologs (SPHs) and inhibited by serpins. However, integration and conservation of the system and its control mechanisms are not fully understood. Here we present biochemical evidence that PO-catalyzed melanin formation, Spätzle-triggered Toll activation, and induced synthesis of antimicrobial peptides are stimulated via hemolymph (serine) protease 5 (HP5) in Previous studies have demonstrated a protease cascade pathway in which HP14 activates proHP21; HP21 activates proPAP2 and proPAP3, which then activate proPO in the presence of a complex of SPH1 and SPH2. We found that both HP21 and PAP3 activate proHP5 by cleavage at ESDR*IIGG. HP5 then cleaves proHP6 at a unique site of LDLH*ILGG. HP6, an ortholog of Persephone, activates both proHP8 and proPAP1. HP8 activates proSpätzle-1, whereas PAP1 cleaves and activates proPO. HP5 is inhibited by serpin-4, serpin-1A, and serpin-1J to regulate its activity. In summary, we have elucidated the physiological roles of HP5, a CLIPB with unique cleavage specificity (cutting after His) that coordinates immune responses in the caterpillar.
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http://dx.doi.org/10.1073/pnas.2004761117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7519321PMC
September 2020

Digestion-related proteins in the tobacco hornworm, Manduca sexta.

Insect Biochem Mol Biol 2020 11 27;126:103457. Epub 2020 Aug 27.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA. Electronic address:

Food digestion is vital for the survival and prosperity of insects. Research on insect digestive enzymes yields knowledge of their structure and function, and potential targets of antifeedants to control agricultural pests. While such enzymes from pest species are more relevant for inhibitor screening, a systematic analysis of their counterparts in a model insect has broader impacts. In this context, we identified a set of 122 digestive enzyme genes from the genome of Manduca sexta, a lepidopteran model related to some major agricultural pests. These genes encode hydrolases of proteins (85), lipids (20), carbohydrates (16), and nucleic acids (1). Gut serine proteases (62) and their noncatalytic homologs (11) in the S1A subfamily are encoded by abundant transcripts whose levels correlate well with larval feeding stages. Aminopeptidases (10), carboxypeptidases (10), and other proteases (3) also participate in dietary protein digestion. A large group of 11 lipases as well as 9 esterases are probably responsible for digesting lipids in diets. The repertoire of carbohydrate hydrolases (16) is relatively small, including two amylases, three maltases, two sucrases, two α-glucosidases, and others. Lysozymes, peptidoglycan amidases, and β-1,3-glucanase may hydrolyze peptidoglycans and glucans to harvest energy and defend the host from microbes on plant leaves. One alkaline nuclease is associated with larval feeding, which is likely responsible for hydrolyzing denatured DNA and RNA undergoing autolysis at a high pH of midgut. Proteomic analysis of the ectoperitrophic fluid from feeding larvae validated at least 131 or 89% of the digestive enzymes and their homologs. In summary, this study provides for the first time a holistic view of the digestion-related proteins in a lepidopteran model insect and clues for comparative research in lepidopteran pests and beyond.
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http://dx.doi.org/10.1016/j.ibmb.2020.103457DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7554134PMC
November 2020

Inhibition of immune pathway-initiating hemolymph protease-14 by Manduca sexta serpin-12, a conserved mechanism for the regulation of melanization and Toll activation in insects.

Insect Biochem Mol Biol 2020 01 4;116:103261. Epub 2019 Nov 4.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA. Electronic address:

A network of serine proteases (SPs) and their non-catalytic homologs (SPHs) activates prophenoloxidase (proPO), Toll pathway, and other insect immune responses. However, integration and conservation of the network and its control mechanisms have not yet been fully understood. Here we present evidence that these responses are initiated through a conserved serine protease and negatively regulated by serpins in two species, Manduca sexta and Anopheles gambiae. We have shown that M. sexta serpin-12 reduces the proteolytic activation of HP6, HP8, proPO activating proteases (PAPs), SPHs, and POs in larval hemolymph, and we hypothesized that these effects are due to the inhibition of the immune pathway-initiating protease HP14. To test whether these changes are due to HP14 inhibition, we isolated a covalent complex of HP14 with serpin-12 from plasma using polyclonal antibodies against the HP14 protease domain or against serpin-12, and confirmed formation of the complex by 2D-electrophoresis, immunoblotting, and mass spectrometry. Upon recognition of bacterial peptidoglycans or fungal β-1,3-glucan, the zymogen proHP14 became active HP14, which formed an SDS-stable complex with serpin-12 in vitro. Activation of proHP21 by HP14 was suppressed by serpin-12, consistent with the decrease in steps downstream of HP21, proteolytic activation of proPAP3, proSPH1/2 and proPO in hemolymph. Guided by the results of phylogenetic analysis, we cloned and expressed A. gambiae proSP217 (an ortholog of HP14) and core domains of A. gambiae serpin-11 and -17. The recombinant SP217 zymogen became active during expression, with cleavage between Tyr and Ile. Both MsHP14 and AgSP217 cleaved MsSerpin-12 and AgSRPN11 at Leu*Ser (P1*P1') and formed complexes in vitro. ProPO activation in M. sexta plasma increased after recombinant AgSP217 had been added, indicating that it may function in a similar manner as the endogenous initiating protease HP14. Based on these data, we propose that inhibition of an initiating modular protease by a serpin may be a common mechanism in holometabolous insects to regulate proPO activation and other protease-induced immune responses.
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http://dx.doi.org/10.1016/j.ibmb.2019.103261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6983340PMC
January 2020

Engineering Dynamic Surface Peptide Networks on Butyrylcholinesterase for Enhanced Organophosphosphorus Anticholinesterase Catalysis.

Chem Res Toxicol 2019 09 28;32(9):1801-1810. Epub 2019 Aug 28.

Department of Physiological Sciences , Oklahoma State University , Stillwater , Oklahoma 74078 , United States.

The single residue mutation of butyrylcholinesterase (BChE) hydrolyzes a number of organophosphosphorus (OP) anticholinesterases. Whereas other BChE active site/proximal mutations have been investigated, none are sufficiently active to be prophylactically useful. In a fundamentally different computer simulations driven strategy, we identified a surface peptide loop (residues 278-285) exhibiting dynamic motions during catalysis and modified it via residue insertions. We evaluated these loop mutants using computer simulations, substrate kinetics, resistance to inhibition, and enzyme reactivation assays using both the choline ester and OP substrates. A slight but significant increase in reactivation was noted with paraoxon with one of the mutants, and changes in and catalytic efficiency were noted in others. Simulations suggested weaker interactions between OP versus choline substrates and the active site of all engineered versions of the enzyme. The results indicate that an improvement of OP anticholinesterase hydrolysis through surface loop engineering may be a more effective strategy in an enzyme with higher intrinsic OP compound hydrolase activity.
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http://dx.doi.org/10.1021/acs.chemrestox.9b00146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7251593PMC
September 2019

Expression and Characterization of Stress Responsive Peptide-1; an Inducer of Antimicrobial Peptide Synthesis.

Biochem Mol Biol (N Y) 2019 May 14;4(3):42-52. Epub 2019 Aug 14.

Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA.

In response to stress conditions such as wounding or infections in insects, several short peptides are processed to act as cytokines that induce AMP gene expression. To study their structure-activity relationship, immune inducibility, tissue specificity, stress responsiveness, and development relatedness, we chemically synthesized stress response peptide-1, a 25-residue peptide with one disulfide bond (SRP1: FGVRVGTCPSGYVRRGTFCFPDDDY). Upon injection of the SRP1 into naïve larvae, several antimicrobial peptide genes were expressed at higher levels. The mRNA levels of SRP1 increased significantly in hemocytes and fat body after larvae were challenged with a mixture of bacteria and β-1,3-glucan. The expression patterns of SRP1 and its target genes are somewhat different from SRP2's, suggesting overlapping yet distinct functions. We elucidated the 3D structure of SRP1 in solution by two-dimensional H-H NMR spectroscopy. The tertiary structure of SRP1 consists of two short β-strands at Y12-R15 and F18-F20, one type-II β-turn at R15-F18 in its well-defined core and is stabilized by a covalent disulfide bond between C8 and C19. The conformational ensemble of SRP1 from extensive atomistic simulation in explicit solvent (with 3.0 μs total effective sampling) shows high consistency with experimental intramolecular NOEs of the core region. The SRP1 core adopts a fold similar to the carboxyl-terminal subdomain of epidermal growth factor (EGF), suggesting that SRP1 may interact with EGF receptor-like molecules to trigger its biological function.
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http://dx.doi.org/10.11648/j.bmb.20190403.12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7685292PMC
May 2019

The three-dimensional structure and recognition mechanism of Manduca sexta peptidoglycan recognition protein-1.

Insect Biochem Mol Biol 2019 05 21;108:44-52. Epub 2019 Mar 21.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA. Electronic address:

Peptidoglycan recognition proteins (PGRPs) recognize bacteria through their unique cell wall constituent, peptidoglycans (PGs). PGRPs are conserved from insects to mammals and all function in antibacterial defense. In the tobacco hornworm Manduca sexta, PGRP1 and microbe binding protein (MBP) interact with PGs and hemolymph protease-14 precursor (proHP14) to yield active HP14. HP14 triggers a serine protease network that produces active phenoloxidase (PO), Spätzle, and other cytokines to stimulate immune responses. PGRP1 binds preferentially to diaminopimelic acid (DAP)-PGs of Gram-negative bacteria and Gram-positive Bacillus and Clostridium species than Lys-PGs of other Gram-positive bacteria. In this study, we synthesized DAP- and Lys-muramyl pentapeptide (MPP) and monitored their associations with M. sexta PGRP1 by surface plasmon resonance. The K values (0.57 μM for DAP-MPP and 45.6 μM for Lys-MPP) agree with the differential recognition of DAP- and Lys-PGs. To reveal its structural basis, we produced the PGRP1 in insect cells and determined its structure at a resolution of 2.1 Å. The protein adopts a fold similar to those from other PGRPs with a classical L-shaped PG-binding groove. A unique loop lining the shallow groove suggests a different ligand-binding mechanism. In summary, this study provided new insights into the PG recognition by PGRPs, a critical first step that initiates the serine protease cascade.
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http://dx.doi.org/10.1016/j.ibmb.2019.03.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7032066PMC
May 2019

Integrated Modeling of Structural Genes Using MCuNovo.

Methods Mol Biol 2019 ;1858:45-57

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, USA.

Correct modeling of protein-coding genes based on genome and cDNA data is a prerequisite for functional studies. Various programs such as MAKER, Cufflinks, Oases, and Trinity have been developed, each with advantages and drawbacks. Manual integration of different models for a single gene is cumbersome and becomes a daunting task for 14,000-18,000 genes in a typical holometabolous insect. We developed methods to evaluate the output of MAKER, Cufflinks, Oases and Trinity and select the best models to constitute the MCOT1.0 set for Manduca sexta, a biochemical model insect. To apply these methods in other organisms, we improved the algorithm (designated MCuNovo Gene Selector) and automated the data processing. In this chapter, we describe background information of algorithm development and how to prepare and run this program.
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http://dx.doi.org/10.1007/978-1-4939-8775-7_5DOI Listing
July 2019

Building a platform for predicting functions of serine protease-related proteins in Drosophila melanogaster and other insects.

Insect Biochem Mol Biol 2018 12 24;103:53-69. Epub 2018 Oct 24.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA. Electronic address:

Serine proteases (SPs) and serine protease homologs (SPHs) play essential roles in insect physiological processes including digestion, defense and development. Studies of insect genomes, transcriptomes and proteomes have generated a vast amount of information on these proteins, dwarfing the biological data acquired from a few model species. The large number and high diversity of homologous sequences makes it a challenge to use the limited functional information for making predictions across a broad taxonomic group of insects. In this work, we have extensively updated the framework of knowledge on the SP-related proteins in Drosophila melanogaster by identifying 52 new SPs/SPHs, classifying the 257 proteins into four groups (CLIP, gut, single- and multi-domain SPs/SPHs), and detecting inherent connections among phylogenetic relationships, genomic locations and expression profiles for 99 of the genes. Information on the existence of specific proteins in eggs, larvae, pupae and adults is presented to facilitate future research. More importantly, we have developed an approach to reveal close homologous or orthologous relationships among SPs/SPHs from D. melanogaster, Anopheles gambiae, Apis mellifera, Manduca sexta, and Tribolium castaneum thus inspiring functional studies in these and other holometabolous insects. This approach is useful for tackling similar problems on large and diverse protein families in other groups of organisms.
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http://dx.doi.org/10.1016/j.ibmb.2018.10.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6358214PMC
December 2018

Manipulation of the silkworm immune system by a metalloprotease from the pathogenic bacterium Pseudomonas aeruginosa.

Dev Comp Immunol 2019 01 24;90:176-185. Epub 2018 Sep 24.

Department of Entomology, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address:

Antimicrobial peptide (AMP) production and melanization are two key humoral immune responses in insects. Induced synthesis of AMPs results from Toll and IMD signal transduction whereas melanization depends on prophenoloxidase (PPO) activation system. During invasion, pathogens produce toxins and other virulent factors to counteract host immune responses. Here we show that the pathways leading to PPO activation and AMP synthesis in the silkworm Bombyx mori are affected by a metalloprotease, named elastase B, secreted by Pseudomonas aeruginosa (PAO1). The metalloprotease gene (lasB) was expressed shortly after PAO1 cells had been injected into the larval silkworm hemocoel, leading to an increase of elastase activity. Injection of the purified PAO1 elastase B into silkworm hemolymph compromised PPO activation. In contrast, the protease caused a level increase of gloverin, an AMP in the hemolymph. To verify our results obtained using the purified elastase B, we infected B. mori with PAO1 ΔlasB mutant and found that PO activity in hemolymph of the PAO1 ΔlasB-infected larvae was significantly higher than that in the wild type-infected. The mutant-inhabited hemolymph had lower levels of gloverin and antimicrobial activity. PAO1 ΔlasB showed a decreased viability in the silkworm hemolymph whereas the host had a lower mortality. In addition, the effects caused by the ΔlasB mutant were restored by a complementary strain. These data collectively indicated that the elastase B produced by PAO1 is an important virulent factor that manipulates the silkworm immune system during infection.
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http://dx.doi.org/10.1016/j.dci.2018.09.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6204220PMC
January 2019

The Manduca sexta serpinome: Analysis of serpin genes and proteins in the tobacco hornworm.

Insect Biochem Mol Biol 2018 11 18;102:21-30. Epub 2018 Sep 18.

Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA. Electronic address:

Members of the serpin superfamily of proteins occur in animals, plants, bacteria, archaea and some viruses. They adopt a variety of physiological functions, including regulation of immune system, modulation of apoptosis, hormone transport and acting as storage proteins. Most members of the serpin family are inhibitors of serine proteinases. In this study, we searched the genome of Manduca sexta and identified 32 serpin genes. We analyzed the structure of these genes and the sequences of their encoded proteins. Three M. sexta genes (serpin-1, serpin-15, and serpin-28) have mutually exclusive alternatively spliced exons encoding the carboxyl-terminal reactive center loop of the protein, which is the site of interaction with target proteases. We discovered that MsSerpin-1 has 14 splicing isoforms, including two undiscovered in previous studies. Twenty-eight of the 32 M. sexta serpins include a putative secretion signal peptide and are predicted to be extracellular proteins. Phylogenetic analysis of serpins in M. sexta and Bombyx mori indicates that 17 are orthologous pairs, perhaps carrying out essential physiological functions. Analysis of the reactive center loop and hinge regions of the protein sequences indicates that 16 of the serpin genes encode proteins that may lack proteinase inhibitor activity. Our annotation and analysis of these serpin genes and their transcript profiles should lead to future advances in experimental study of their functions in insect biochemistry.
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http://dx.doi.org/10.1016/j.ibmb.2018.09.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6249112PMC
November 2018

Manduca sexta hemolymph protease-2 (HP2) activated by HP14 generates prophenoloxidase-activating protease-2 (PAP2) in wandering larvae and pupae.

Insect Biochem Mol Biol 2018 10 8;101:57-65. Epub 2018 Aug 8.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA. Electronic address:

Melanization is a universal defense mechanism of insects against microbial infection. During this response, phenoloxidase (PO) is activated from its precursor by prophenoloxidase activating protease (PAP), the terminal enzyme of a serine protease (SP) cascade. In the tobacco hornworm Manduca sexta, hemolymph protease-14 (HP14) is autoactivated from proHP14 to initiate the protease cascade after host proteins recognize invading pathogens. HP14, HP21, proHP1*, HP6, HP8, PAP1-3, and non-catalytic serine protease homologs (SPH1 and SPH2) constitute a portion of the extracellular SP-SPH system to mediate melanization and other immune responses. Here we report the expression, purification, and functional characterization of M. sexta HP2. The HP2 precursor is synthesized in hemocytes, fat body, integument, nerve and trachea. Its mRNA level is low in fat body of 5th instar larvae before wandering stage; abundance of the protein in hemolymph displays a similar pattern. HP2 exists as an active enzyme in plasma of the wandering larvae and pupae in the absence of an infection. HP14 cleaves proHP2 to yield active HP2. After incubating active HP2 with larval hemolymph, we detected higher levels of PO activity, i.e. an enhancement of proPO activation. HP2 cleaved proPAP2 (but not proPAP3 or proPAP1) to yield active PAP2, responsible for a major increase in IEARpNA hydrolysis. PAP2 activates proPOs in the presence of a cofactor of SPH1 and SPH2. In summary, we have identified a new member of the proPO activation system and reconstituted a pathway of HP14-HP2-PAP2-PO. Since high levels of HP2 mRNA were present in integument and active HP2 in plasma of wandering larvae, HP2 likely plays a role in cuticle melanization during pupation and protects host from microbial infection in a soil environment.
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http://dx.doi.org/10.1016/j.ibmb.2018.08.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6163074PMC
October 2018

Clip domain prophenoloxidase activating protease is required for Ostrinia furnacalis Guenée to defend against bacterial infection.

Dev Comp Immunol 2018 10 2;87:204-215. Epub 2018 Jul 2.

Department of Plant Protection, College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, Jiangsu 225009, China.

The prophenoloxidase (PPO) activating system in insects plays an important role in defense against microbial invasion. In this paper, we identified a PPO activating protease (designated OfPAP) containing a 1203 bp open reading frame encoding a 400-residue protein composed of two clip domains and a C-terminal serine protease domain from Ostrinia furnacalis. SignalP analysis revealed a putative signal peptide of 18 residues. The mature OfPAP was predicted to be 382 residues long with a calculated M of 44.8 kDa and pI of 6.66. Multiple sequence alignment and phylogenetic analysis indicated that OfPAP was orthologous to the PAPs in the other lepidopterans. A large increase of the transcript levels was observed in hemocytes at 4 h post injection (hpi) of killed Bacillus subtilis, whereas its level in integument increased continuously from 4 to 12 hpi in the challenged larvae and began to decline at 24 hpi. After OfPAP expression had been silenced, the median lethal time (LT) of Escherichia coli-infected larvae (1.0 day) became significantly lower than that of E. coli-infected wild-type (3.0 days, p < 0.01). A 3.5-fold increase in E. coli colony forming units occurred in larval hemolymph of the OfPAP knockdown larvae, as compared with that of the control larvae not injected with dsRNA. There were notable decreases in PO and IEARase activities in hemolymph of the OfPAP knockdown larvae. In summary, we have demonstrated that OfPAP is a component of the PPO activation system, likely by functioning as a PPO activating protease in O. furnacalis larvae.
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http://dx.doi.org/10.1016/j.dci.2018.06.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6093219PMC
October 2018

Manduca sexta serpin-12 controls the prophenoloxidase activation system in larval hemolymph.

Insect Biochem Mol Biol 2018 08 23;99:27-36. Epub 2018 May 23.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA. Electronic address:

Insect prophenoloxidase activation is coordinated by a serine protease network, which is regulated by serine protease inhibitors of the serpin superfamily. The enzyme system also leads to proteolytic processing of a Spätzle precursor. Binding of Spätzle to a Toll receptor turns on a signaling pathway to induce the synthesis of defense proteins. Previous studies of the tobacco hornworm Manduca sexta have revealed key members of the protease cascade, which generates phenoloxidase for melanogenesis and Spätzle to induce immunity-related genes. Here we provide evidence that M. sexta serpin-12 regulates hemolymph protease-14 (HP14), an initiating protease of the cascade. This inhibitor, unlike the other serpins characterized in M. sexta, has an amino-terminal extension rich in hydrophilic residues and an unusual P1 residue (Leu) right before the scissile bond cleaved by a target protease. Serpins with similarities to serpin-12, including Drosophila Necrotic, were identified in a wide range of insects including flies, moths, wasps, beetles, and two hemimetabolous species. The serpin-12 mRNA is present at low, constitutive levels in larval fat body and hemocytes and becomes more abundant after an immune challenge. We produced the serpin-12 core domain (serpin-12ΔN) in insect cells and in Escherichia coli and demonstrated its inhibition of human cathepsin G, bovine α-chymotrypsin, and porcine pancreatic elastase. MALDI-TOF analysis of the reaction mixtures confirmed the predicted P1 residue of Leu. Supplementation of larval plasma samples with the serpin-12ΔN decreased prophenoloxidase activation elicited by microbial cells and reduced the proteolytic activation of the protease precursors of HP6, HP8, PAPs, and other serine protease-related proteins. After incubation of plasma stimulated with peptidoglycan, a 72 kDa protein appeared, which was recognized by polyclonal antibodies against both serpin-12 and HP14, suggesting that a covalent serpin-protease complex formed when serpin-12 inhibited HP14. Together, these data suggest that M. sexta serpin-12 inhibits HP14 to regulate melanization and antimicrobial peptide induction.
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http://dx.doi.org/10.1016/j.ibmb.2018.05.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5997545PMC
August 2018

An analysis of 67 RNA-seq datasets from various tissues at different stages of a model insect, Manduca sexta.

BMC Genomics 2017 Oct 17;18(1):796. Epub 2017 Oct 17.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA.

Background: Manduca sexta is a large lepidopteran insect widely used as a model to study biochemistry of insect physiological processes. As a part of its genome project, over 50 cDNA libraries have been analyzed to profile gene expression in different tissues and life stages. While the RNA-seq data were used to study genes related to cuticle structure, chitin metabolism and immunity, a vast amount of the information has not yet been mined for understanding the basic molecular biology of this model insect. In fact, the basic features of these data, such as composition of the RNA-seq reads and lists of library-correlated genes, are unclear. From an extended view of all insects, clear-cut tempospatial expression data are rarely seen in the largest group of animals including Drosophila and mosquitoes, mainly due to their small sizes.

Results: We obtained the transcriptome data, analyzed the raw reads in relation to the assembled genome, and generated heatmaps for clustered genes. Library characteristics (tissues, stages), number of mapped bases, and sequencing methods affected the observed percentages of genome transcription. While up to 40% of the reads were not mapped to the genome in the initial Cufflinks gene modeling, we identified the causes for the mapping failure and reduced the number of non-mappable reads to <8%. Similarities between libraries, measured based on library-correlated genes, clearly identified differences among tissues or life stages. We calculated gene expression levels, analyzed the most abundantly expressed genes in the libraries. Furthermore, we analyzed tissue-specific gene expression and identified 18 groups of genes with distinct expression patterns.

Conclusion: We performed a thorough analysis of the 67 RNA-seq datasets to characterize new genomic features of M. sexta. Integrated knowledge of gene functions and expression features will facilitate future functional studies in this biochemical model insect.
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http://dx.doi.org/10.1186/s12864-017-4147-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5645894PMC
October 2017

Serpin-9 and -13 regulate hemolymph proteases during immune responses of Manduca sexta.

Insect Biochem Mol Biol 2017 11 5;90:71-81. Epub 2017 Oct 5.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA. Electronic address:

Serpins are a superfamily of proteins, most of which inhibit cognate serine proteases by forming inactive acyl-enzyme complexes. In the tobacco hornworm Manduca sexta, serpin-1, -3 through -7 negatively regulate a hemolymph serine protease system that activates precursors of the serine protease homologs (SPHs), phenoloxidases (POs), Spätzles, and other cytokines. Here we report the cloning and characterization of M. sexta serpin-9 and -13. Serpin-9, a 402-residue protein most similar to Drosophila Spn77Ba, has R at the P1 position right before the cleavage site; Serpin-13, a 444-residue ortholog of Drosophila Spn28Dc, is longer than the other seven serpins and has R as the P1 residue. Both serpins are mainly produced in fat body and secreted into plasma to function. While their mRNA and protein levels were not up-regulated upon immune challenge, they blocked protease activities and affected proPO activation in hemolymph. Serpin-9 inhibited human neutrophil elastase, cathepsin G, trypsin, and chymotrypsin to different extents; serpin-13 reduced trypsin activity to approximately 10% at a molar ratio of 4:1 (serpin: enzyme). Serpin-9 was cleaved at Arg by the enzymes with different specificity, but serpin-13 had four P1 sites (Arg for trypsin-like proteases, Gly and Ala for the elastase and Thr for cathepsin G). Supplementation of induced cell-free hemolymph (IP, P for plasma) with recombinant serpin-9 did not noticeably affect proPO activation, but slightly reduced the PO activity increase after 0-50% ammonium sulfate fraction of the IP had been elicited by bacteria. In comparison, addition of recombinant serpin-13 significantly inhibited proPO activation in IP and the suppression was stronger in the fraction of IP. Serpin-9- and -13-containing protein complexes were isolated from IP using their antibodies. Hemolymph protease-1 precursor (proHP1), HP6 and HP8 were found to be associated with serpin-9, whereas proHP1, HP2 and HP6 were pulled downed with serpin-13. These results indicate that both serpins regulate immune proteases in hemolymph of M. sexta larvae.
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http://dx.doi.org/10.1016/j.ibmb.2017.09.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5673523PMC
November 2017

Serine protease-related proteins in the malaria mosquito, Anopheles gambiae.

Insect Biochem Mol Biol 2017 09 2;88:48-62. Epub 2017 Aug 2.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA. Electronic address:

Insect serine proteases (SPs) and serine protease homologs (SPHs) participate in digestion, defense, development, and other physiological processes. In mosquitoes, some clip-domain SPs and SPHs (i.e. CLIPs) have been investigated for possible roles in antiparasitic responses. In a recent test aimed at improving quality of gene models in the Anopheles gambiae genome using RNA-seq data, we observed various discrepancies between gene models in AgamP4.5 and corresponding sequences selected from those modeled by Cufflinks, Trinity and Bridger. Here we report a comparative analysis of the 337 SP-related proteins in A. gambiae by examining their domain structures, sequence diversity, chromosomal locations, and expression patterns. One hundred and ten CLIPs contain 1 to 5 clip domains in addition to their protease domains (PDs) or non-catalytic, protease-like domains (PLDs). They are divided into five subgroups: CLIPAs (22) are clip-PLD; CLIPBs (29), CLIPCs (12) and CLIPDs (14) are mainly clip-PD; most CLIPEs (33) have a domain structure of PD/PLD-PLD-clip-PLD. While expression of the CLIP genes in group-1 is generally low and detected in various tissue- and stage-specific RNA-seq libraries, some putative GPs/GPHs (i.e. single domain gut SPs/SPHs) in group-2 are highly expressed in midgut, whole larva or whole adult libraries. In comparison, 46 SPs, 26 SPHs, and 37 multi-domain SPs/SPHs (i.e. PD/PLD-PLD) in group-3 do not seem to be specifically expressed in digestive tract. There are 16 SPs and 2 SPH containing other types of putative regulatory domains (e.g. LDLa, CUB, Gd). Of the 337 SP and SPH genes, 159 were sorted into 46 groups (2-8 members/group) based on similar phylogenetic tree position, chromosomal location, and expression profile. This information and analysis, including improved gene models and protein sequences, constitute a solid foundation for functional analysis of the SP-related proteins in A. gambiae.
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http://dx.doi.org/10.1016/j.ibmb.2017.07.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5586530PMC
September 2017

Improving the baculovirus expression vector system with vankyrin-enhanced technology.

Biotechnol Prog 2017 11 6;33(6):1496-1507. Epub 2017 Jul 6.

GlycoBac LLC, Laramie, Wyoming.

The baculovirus expression vector system (BEVS) is a widely used platform for the production of recombinant eukaryotic proteins. However, the BEVS has limitations in comparison to other higher eukaryotic expression systems. First, the insect cell lines used in the BEVS cannot produce glycoproteins with complex-type N-glycosylation patterns. Second, protein production is limited as cells die and lyse in response to baculovirus infection. To delay cell death and lysis, we transformed several insect cell lines with an expression plasmid harboring a vankyrin gene (P-vank-1), which encodes an anti-apoptotic protein. Specifically, we transformed Sf9 cells, Trichoplusia ni High Five cells, and SfSWT-4 cells, which can produce glycoproteins with complex-type N-glycosylation patterns. The latter was included with the aim to increase production of glycoproteins with complex N-glycans, thereby overcoming the two aforementioned limitations of the BEVS. To further increase vankyrin expression levels and further delay cell death, we also modified baculovirus vectors with the P-vank-1 gene. We found that cell lysis was delayed and recombinant glycoprotein yield increased when SfSWT-4 cells were infected with a vankyrin-encoding baculovirus. A synergistic effect in elevated levels of recombinant protein production was observed when vankyrin-expressing cells were combined with a vankyrin-encoding baculovirus. These effects were observed with various model proteins including medically relevant therapeutic proteins. In summary, we found that cell lysis could be delayed and recombinant protein yields could be increased by using cell lines constitutively expressing vankyrin or vankyrin-encoding baculovirus vectors. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1496-1507, 2017.
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http://dx.doi.org/10.1002/btpr.2516DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5786172PMC
November 2017

Hemolymph proteins of Anopheles gambiae larvae infected by Escherichia coli.

Dev Comp Immunol 2017 09 19;74:110-124. Epub 2017 Apr 19.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA; Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA. Electronic address:

Anopheles gambiae is a major vector of human malaria and its immune system in part determines the fate of ingested parasites. Proteins, hemocytes and fat body in hemolymph are critical components of this system, mediating both humoral and cellular defenses. Here we assessed differences in the hemolymph proteomes of water- and E. coli-pricked mosquito larvae by a gel-LC-MS approach. Among the 1756 proteins identified, 603 contained a signal peptide but accounted for two-third of the total protein amount on the quantitative basis. The sequence homology search indicated that 233 of the 1756 may be related to defense. In general, we did not detect substantial differences between the control and induced plasma samples in terms of protein numbers or levels. Protein distributions in the gel slices suggested post-translational modifications (e.g. proteolysis) and formation of serpin-protease complexes and high Mr immune complexes. Based on the twenty-five most abundant proteins, we further suggest that major functions of the larval hemolymph are storage, transport, and immunity. In summary, this study provided first data on constitution, levels, and possible functions of hemolymph proteins in the mosquito larvae, reflecting complex changes occurring in the fight against E. coli infection.
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http://dx.doi.org/10.1016/j.dci.2017.04.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5531190PMC
September 2017

Manduca sexta hemolymph protease-1, activated by an unconventional non-proteolytic mechanism, mediates immune responses.

Insect Biochem Mol Biol 2017 05 31;84:23-31. Epub 2017 Mar 31.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA. Electronic address:

Tissue damage or pathogen invasion triggers the auto-proteolysis of an initiating serine protease (SP), rapidly leading to sequential cleavage activation of other cascade members to set off innate immune responses in insects. Recently, we presented evidence that Manduca sexta hemolymph protease-1 zymogen (proHP1) is a member of the SP system in this species, and may activate proHP6. HP6 stimulates melanization and induces antimicrobial peptide synthesis. Here we report that proHP1 adopts an active conformation (*) to carry out its function, without a requirement for proteolytic activation. Affinity chromatography using HP1 antibodies isolated from induced hemolymph the 48 kDa proHP1 and also a 90 kDa band (detected by SDS-PAGE under reducing conditions) containing proHP1 and several serpins, as revealed by mass spectrometric analysis. Identification of tryptic peptides from these 90 kDa complexes included peptides from the amino-terminal regulatory part of proHP1, indicating that proHP1* was not cleaved, and that it had formed a complex with the serpins. As suicide inhibitors, serpins form SDS-stable, acyl-complexes when they are attacked by active proteases, indicating that proHP1* was catalytically active. Detection of M. sexta serpin-1, 4, 9, 13 and smaller amounts of serpin-3, 5, 6 in the complexes suggests that it is regulated by multiple serpins in hemolymph. We produced site-directed mutants of proHP1b for cleavage by bovine blood coagulation factor Xa at the designed proteolytic activation site, to generate a form of proHP1b that could be activated by Factor Xa. However, proHP1b cut by Factor Xa failed to activate proHP6 and, via HP6, proHP8 or proPAP1. This negative result is consistent with the suggestion that proHP1* is a physiological mediator of immune responses. Further research is needed to investigate the conformational change that results in conversion of proHP1 to active proHP1*.
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http://dx.doi.org/10.1016/j.ibmb.2017.03.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5461656PMC
May 2017

Prophenoloxidase activation and antimicrobial peptide expression induced by the recombinant microbe binding protein of Manduca sexta.

Insect Biochem Mol Biol 2017 04 29;83:35-43. Epub 2016 Oct 29.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, United States. Electronic address:

Manduca sexta microbe binding protein (MBP) is a member of the β-1,3-glucanase-related protein superfamily that includes Gram-negative bacteria-binding proteins (GNBPs), β-1,3-glucan recognition proteins (βGRPs), and β-1,3-glucanases. Our previous and current studies showed that the purified MBP from baculovirus-infected insect cells had stimulated prophenoloxidase (proPO) activation in the hemolymph of naïve and immune challenged larvae and that supplementation of the exogenous MBP and peptidoglycans (PGs) had caused synergistic increases in PO activity. To explore the underlying mechanism, we separated by SDS-PAGE naïve and induced larval plasma treated with buffer or MBP and detected on immunoblots changes in intensity and/or mobility of hemolymph (serine) proteases [HP14, HP21, HP6, HP8, proPO-activating proteases (PAPs) 1-3] and their homologs (SPH1, SPH2). In a nickel pull-down assay, we observed association of MBP with proHP14 (slightly), βGRP2, PG recognition protein-1 (PGRP1, indirectly), SPH1, SPH2, and proPO2. Further experiments indicated that diaminopimelic acid (DAP) or Lys PG, MBP, PGRP1, and proHP14 together trigger the proPO activation system in a Ca-dependent manner. Injection of the recombinant MBP into the 5th instar naïve larvae significantly induced the expression of several antimicrobial peptide genes, revealing a possible link between HP14 and immune signal transduction. Together, these results suggest that the recognition of Gram-negative or -positive bacteria via their PGs induces the melanization and Toll pathways in M. sexta.
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http://dx.doi.org/10.1016/j.ibmb.2016.10.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5461653PMC
April 2017

Solution Structure and Expression Profile of an Insect Cytokine: Manduca sexta Stress Response Peptide-2.

Protein Pept Lett 2017 ;24(1):3-11

Department of Biochemistry and Molecular Biophysics, Kansas State Universities, Manhattan, KS 66506, USA.

Manduca sexta stress response peptide-2 (SRP2) is predicted to be a 25-residue peptide (FGVKDGKCPSGRVRRLGICVPDDDY), which may function as an insect cytokine to regulate immune responses. Produced as an inactive precursor, endogenous proSRP2 is probably converted to active SRP2 by limited proteolysis in response to invading pathogens, along with prophenoloxidase and pro-Spätzle activation. In addition to immunity, SRP2 may control head morphogenesis or other developmental processes in the lepidopteran insect. We have examined the profiles of SRP2 gene expression in terms of immune induction capacity, tissue specificity, and developmental changes. To gain insights into its functions, we chemically synthesized SRP2, injected the peptide solution into naïve larvae, and detected significant up-regulation of several antimicrobial peptide genes. We determined the 3D molecular structure in solution of SRP2 by two-dimensional 1H-1H NMR spectroscopy. SRP2 has an ordered structure, which is composed of two short β-strands at regions R12 - R15 and I18 - V20, one type-I' β-turn at region R15 - I18, and a half turn at region C8 - S10 in its welldefined core stabilized by a covalent disulfide bond between C8 and C19. The secondary and tertiary structures are further stabilized by hydrogen bonds. Possible relationships between the structure and function are also discussed.
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http://dx.doi.org/10.2174/0929866524666161121142840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5596513PMC
March 2017

Multifaceted biological insights from a draft genome sequence of the tobacco hornworm moth, Manduca sexta.

Insect Biochem Mol Biol 2016 09 12;76:118-147. Epub 2016 Aug 12.

Centre of Systems Biology, Biomedical Research Foundation, Academy of Athens, Athens, Greece.

Manduca sexta, known as the tobacco hornworm or Carolina sphinx moth, is a lepidopteran insect that is used extensively as a model system for research in insect biochemistry, physiology, neurobiology, development, and immunity. One important benefit of this species as an experimental model is its extremely large size, reaching more than 10 g in the larval stage. M. sexta larvae feed on solanaceous plants and thus must tolerate a substantial challenge from plant allelochemicals, including nicotine. We report the sequence and annotation of the M. sexta genome, and a survey of gene expression in various tissues and developmental stages. The Msex_1.0 genome assembly resulted in a total genome size of 419.4 Mbp. Repetitive sequences accounted for 25.8% of the assembled genome. The official gene set is comprised of 15,451 protein-coding genes, of which 2498 were manually curated. Extensive RNA-seq data from many tissues and developmental stages were used to improve gene models and for insights into gene expression patterns. Genome wide synteny analysis indicated a high level of macrosynteny in the Lepidoptera. Annotation and analyses were carried out for gene families involved in a wide spectrum of biological processes, including apoptosis, vacuole sorting, growth and development, structures of exoskeleton, egg shells, and muscle, vision, chemosensation, ion channels, signal transduction, neuropeptide signaling, neurotransmitter synthesis and transport, nicotine tolerance, lipid metabolism, and immunity. This genome sequence, annotation, and analysis provide an important new resource from a well-studied model insect species and will facilitate further biochemical and mechanistic experimental studies of many biological systems in insects.
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http://dx.doi.org/10.1016/j.ibmb.2016.07.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5010457PMC
September 2016

In search of a function of Manduca sexta hemolymph protease-1 in the innate immune system.

Insect Biochem Mol Biol 2016 09 23;76:1-10. Epub 2016 Jun 23.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, United States. Electronic address:

Extracellular serine protease cascades mediate immune signaling and responses in insects. In the tobacco hornworm Manduca sexta, nearly 30 serine proteases (SPs) and their homologs (SPHs) are cloned from hemocytes and fat body. Some of them participate in prophenoloxidase (proPO) activation and proSpätzle processing. Here we report the cDNA cloning of hemolymph protease-1b (HP1b), which is 90% identical and 95% similar to HP1a (formerly HP1). The HP1a and HP1b mRNA levels in hemocytes was down- and up-regulated after an immune challenge, respectively. Quantitative real-time polymerase chain reactions revealed their tissue-specific and development-dependent expression, mostly in hemocytes of the feeding larvae. We isolated HP1 precursor (proHP1) from larval hemolymph and observed micro-heterogeneity caused by N-linked glycosylation. Supplementation of the purified proHP1 to plasma samples from naïve larvae or induced ones injected with bacteria caused a small PO activity increase, much lower than those elicited by recombinant proHP1a/b, but no proteolytic cleavage was detected in the zymogens. Incubation of proHP1a/b or their catalytic domains with a cationic detergent, cetylpyridinium chloride, induced an amidase activity that hydrolyzed LDLH-p-nitroanilide. Since LDLH corresponds to the P4-P1 region before the proteolytic activation site of proHP6, we propose that the active but uncleaved proHP1 may cut proHP6 to generate HP6 that in turn activates proPAP1 and proHP8. The catalytic domain of HP1a/b, which by itself does not activate purified proHP6 or hydrolyze LDLH-p-nitroanilide, somehow generated active HP6, HP8, PAP1 and PO in plasma. Together, these results indicate that proHP1 participates in the proPO activation system, although detailed mechanism needs further exploration.
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http://dx.doi.org/10.1016/j.ibmb.2016.06.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5011066PMC
September 2016

Changes in the Plasma Proteome of Manduca sexta Larvae in Relation to the Transcriptome Variations after an Immune Challenge: Evidence for High Molecular Weight Immune Complex Formation.

Mol Cell Proteomics 2016 Apr 25;15(4):1176-87. Epub 2016 Jan 25.

From the ‡Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078;

Manduca sextais a lepidopteran model widely used to study insect physiological processes, including innate immunity. In this study, we explored the proteomes of cell-free hemolymph from larvae injected with a sterile buffer (C for control) or a mixture of bacteria (I for induced). Of the 654 proteins identified, 70 showed 1.67 to >200-fold abundance increases after the immune challenge; 51 decreased to 0-60% of the control levels. While there was no strong parallel between plasma protein levels and their transcript levels in hemocytes or fat body, the mRNA level changes (i.e.I/C ratios of normalized read numbers) in the tissues concurred with their protein level changes (i.e.I/C ratios of normalized spectral counts) with correlation coefficients of 0.44 and 0.57, respectively. Better correlations support that fat body contributes a more significant portion of the plasma proteins involved in various aspects of innate immunity. Consistently, ratios of mRNA and protein levels were better correlated for immunity-related proteins than unrelated ones. There is a set of proteins whose apparent molecular masses differ considerably from the calculatedMr's, suggestive of posttranslational modifications. In addition, some lowMrproteins were detected in the range of 80 to >300 kDa on a reducing SDS-polyacrylamide gel, indicating the existence of highMrcovalent complexes. We identified 30 serine proteases and their homologs, 11 of which are known members of an extracellular immune signaling network. Along with our quantitative transcriptome data, the protein identification, inducibility, and association provide leads toward a focused exploration of humoral immunity inM. sexta.
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http://dx.doi.org/10.1074/mcp.M115.054296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4824848PMC
April 2016

[Design and study of a new device for low temperature intravenous infusion].

Zhonghua Wei Zhong Bing Ji Jiu Yi Xue 2016 Jan;28(1):76-9

Department of Critical Care Medicine, Foshan Hospital of Traditional Chinese Medicine, Foshan 528000, Guangdong, China. Corresponding author: Ma Mingyuan, Email:

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http://dx.doi.org/10.3760/cma.j.issn.2095-4352.2016.01.015DOI Listing
January 2016

The structure of a prophenoloxidase (PPO) from Anopheles gambiae provides new insights into the mechanism of PPO activation.

BMC Biol 2016 Jan 5;14. Epub 2016 Jan 5.

Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK, 74078, USA.

Background: Phenoloxidase (PO)-catalyzed melanization is a universal defense mechanism of insects against pathogenic and parasitic infections. In mosquitos such as Anopheles gambiae, melanotic encapsulation is a resistance mechanism against certain parasites that cause malaria and filariasis. PO is initially synthesized by hemocytes and released into hemolymph as inactive prophenoloxidase (PPO), which is activated by a serine protease cascade upon recognition of foreign invaders. The mechanisms of PPO activation and PO catalysis have been elusive.

Results: Herein, we report the crystal structure of PPO8 from A. gambiae at 2.6 Å resolution. PPO8 forms a homodimer with each subunit displaying a classical type III di-copper active center. Our molecular docking and mutagenesis studies revealed a new substrate-binding site with Glu364 as the catalytic residue responsible for the deprotonation of mono- and di-phenolic substrates. Mutation of Glu364 severely impaired both the monophenol hydroxylase and diphenoloxidase activities of AgPPO8. Our data suggested that the newly identified substrate-binding pocket is the actual site for catalysis, and PPO activation could be achieved without withdrawing the conserved phenylalanine residue that was previously deemed as the substrate 'placeholder'.

Conclusions: We present the structural and functional data from a mosquito PPO. Our results revealed a novel substrate-binding site with Glu364 identified as the key catalytic residue for PO enzymatic activities. Our data offered a new model for PPO activation at the molecular level, which differs from the canonical mechanism that demands withdrawing a blocking phenylalanine residue from the previously deemed substrate-binding site. This study provides new insights into the mechanisms of PPO activation and enzymatic catalysis of PO.
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http://dx.doi.org/10.1186/s12915-015-0225-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4700666PMC
January 2016