Publications by authors named "Geneviève Bart"

27 Publications

  • Page 1 of 1

Characterization of nucleic acids from extracellular vesicle-enriched human sweat.

BMC Genomics 2021 Jun 9;22(1):425. Epub 2021 Jun 9.

Faculty of Biochemistry and Molecular Medicine, Disease Networks Research Unit, Laboratory of Developmental Biology, Kvantum Institute, Infotech Oulu, University of Oulu, 90014 University of Oulu, Oulu, Finland.

Background: The human sweat is a mixture of secretions from three types of glands: eccrine, apocrine, and sebaceous. Eccrine glands open directly on the skin surface and produce high amounts of water-based fluid in response to heat, emotion, and physical activity, whereas the other glands produce oily fluids and waxy sebum. While most body fluids have been shown to contain nucleic acids, both as ribonucleoprotein complexes and associated with extracellular vesicles (EVs), these have not been investigated in sweat. In this study we aimed to explore and characterize the nucleic acids associated with sweat particles.

Results: We used next generation sequencing (NGS) to characterize DNA and RNA in pooled and individual samples of EV-enriched sweat collected from volunteers performing rigorous exercise. In all sequenced samples, we identified DNA originating from all human chromosomes, but only the mitochondrial chromosome was highly represented with 100% coverage. Most of the DNA mapped to unannotated regions of the human genome with some regions highly represented in all samples. Approximately 5 % of the reads were found to map to other genomes: including bacteria (83%), archaea (3%), and virus (13%), identified bacteria species were consistent with those commonly colonizing the human upper body and arm skin. Small RNA-seq from EV-enriched pooled sweat RNA resulted in 74% of the trimmed reads mapped to the human genome, with 29% corresponding to unannotated regions. Over 70% of the RNA reads mapping to an annotated region were tRNA, while misc. RNA (18,5%), protein coding RNA (5%) and miRNA (1,85%) were much less represented. RNA-seq from individually processed EV-enriched sweat collection generally resulted in fewer percentage of reads mapping to the human genome (7-45%), with 50-60% of those reads mapping to unannotated region of the genome and 30-55% being tRNAs, and lower percentage of reads being rRNA, LincRNA, misc. RNA, and protein coding RNA.

Conclusions: Our data demonstrates that sweat, as all other body fluids, contains a wealth of nucleic acids, including DNA and RNA of human and microbial origin, opening a possibility to investigate sweat as a source for biomarkers for specific health parameters.
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http://dx.doi.org/10.1186/s12864-021-07733-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8188706PMC
June 2021

Secreted Extracellular Vesicle Molecular Cargo as a Novel Liquid Biopsy Diagnostics of Central Nervous System Diseases.

Int J Mol Sci 2021 Mar 23;22(6). Epub 2021 Mar 23.

Cancer Biology & Epigenetics Group, Research Center, Portuguese Oncology Institute of Porto (CI-IPOP), R. Dr. António Bernardino de Almeida, 4200-072 Porto, Portugal.

Secreted extracellular vesicles (EVs) are heterogeneous cell-derived membranous granules which carry a large diversity of molecules and participate in intercellular communication by transferring these molecules to target cells by endocytosis. In the last decade, EVs' role in several pathological conditions, from etiology to disease progression or therapy evasion, has been consolidated, including in central nervous system (CNS)-related disorders. For this review, we performed a systematic search of original works published, reporting the presence of molecular components expressed in the CNS via EVs, which have been purified from plasma, serum or cerebrospinal fluid. Our aim is to provide a list of molecular EV components that have been identified from both nonpathological conditions and the most common CNS-related disorders. We discuss the methods used to isolate and enrich EVs from specific CNS-cells and the relevance of its components in each disease context.
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http://dx.doi.org/10.3390/ijms22063267DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8004928PMC
March 2021

MicroRNAs in Extracellular Vesicles in Sweat Change in Response to Endurance Exercise.

Front Physiol 2020 15;11:676. Epub 2020 Jul 15.

Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland.

Background: To date, microRNAs (miRs) carried in extracellular vesicles (EVs) in response to exercise have been studied in blood but not in non-invasively collectable body fluids. In the present study, we examined whether six exercise-responsive miRs, miRs-21, -26, -126, -146, -221, and -222, respond to acute endurance exercise stimuli of different intensities in sweat.

Methods: We investigated the response of miRs isolated from sweat and serum EVs to three endurance exercise protocols: (1) maximal aerobic capacity (VO ), (2) anaerobic threshold (AnaT), and (3) aerobic threshold (AerT) tests. Sauna bathing was used as a control test to induce sweating through increased body temperature in the absence of exercise. All protocols were performed by the same subjects ( = 8, three males and five females). The occurrence of different miR carriers in sweat and serum was investigated via EV markers (CD9, CD63, and TSG101), an miR-carrier protein (AGO2), and an HDL-particle marker (APOA1) with Western blot. Correlations between miRs in sweat and serum (post-sample) were examined.

Results: Of the studied miR carrier markers, sweat EV fractions expressed CD63 and, very weakly, APOA1, while the serum EV fraction expressed all the studied markers. In sweat EVs, miR-21 level increased after AerT and miR-26 after all the endurance exercise tests compared with the Sauna ( < 0.050). miR-146 after AnaT correlated to sweat and serum EV samples ( = 0.881, = 0.004).

Conclusion: Our preliminary study is the first to show that, in addition to serum, sweat EVs carry miRs. Interestingly, we observed that miRs-21 and -26 in sweat EVs respond to endurance exercise of different intensities. Our data further confirmed that miR responses to endurance exercise in sweat and serum were triggered by exercise and not by increased body temperature. Our results highlight that sweat possesses a unique miR carrier content that should be taken into account when planning analyses from sweat as a substitute for serum.
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http://dx.doi.org/10.3389/fphys.2020.00676DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7373804PMC
July 2020

Complex role of peroxisome proliferator activator receptors (PPARs) in nociception.

Scand J Pain 2015 Oct 1;9(1):70-71. Epub 2015 Oct 1.

A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Neulaniementie 2, Kuopio 70211, Kuopio, Finland.

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http://dx.doi.org/10.1016/j.sjpain.2015.08.006DOI Listing
October 2015

Extracellular ATP activates hyaluronan synthase 2 () in epidermal keratinocytes via P2Y, Ca signaling, and MAPK pathways.

Biochem J 2018 05 24;475(10):1755-1772. Epub 2018 May 24.

Institute of Biomedicine, University of Eastern Finland, FI-70211 Kuopio, Finland.

Extracellular nucleotides are used as signaling molecules by several cell types. In epidermis, their release is triggered by insults such as ultraviolet radiation, barrier disruption, and tissue wounding, and by specific nerve terminals firing. Increased synthesis of hyaluronan, a ubiquitous extracellular matrix glycosaminoglycan, also occurs in response to stress, leading to the attractive hypothesis that nucleotide signaling and hyaluronan synthesis could also be linked. In HaCaT keratinocytes, ATP caused a rapid and strong but transient activation of hyaluronan synthase 2 () expression via protein kinase C-, Ca/calmodulin-dependent protein kinase II-, mitogen-activated protein kinase-, and calcium response element-binding protein-dependent pathways by activating the purinergic P2Y receptor. Smaller but more persistent up-regulation of and , and delayed up-regulation of were also observed. Accumulation of peri- and extracellular hyaluronan followed 4-6 h after stimulation, an effect further enhanced by the hyaluronan precursor glucosamine. AMP and adenosine, the degradation products of ATP, markedly inhibited expression and, despite concomitant up-regulation of and , inhibited hyaluronan synthesis. Functionally, ATP moderately increased cell migration, whereas AMP and adenosine had no effect. Our data highlight the strong influence of adenosinergic signaling on hyaluronan metabolism in human keratinocytes. Epidermal insults are associated with extracellular ATP release, as well as rapid up-regulation of /, , and hyaluronan synthesis, and we show here that the two phenomena are linked. Furthermore, as ATP is rapidly degraded, the opposite effects of its less phosphorylated derivatives facilitate a rapid shut-off of the hyaluronan response, providing a feedback mechanism to prevent excessive reactions when more persistent signals are absent.
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http://dx.doi.org/10.1042/BCJ20180054DOI Listing
May 2018

Exosomes as secondary inductive signals involved in kidney organogenesis.

J Extracell Vesicles 2018 23;7(1):1422675. Epub 2018 Jan 23.

Biocenter Oulu, Laboratory of Developmental Biology, InfoTech Oulu, Center for Cell Matrix Research, Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland.

The subfraction of extracellular vesicles, called exosomes, transfers biological molecular information not only between cells but also between tissues and organs as nanolevel signals. Owing to their unique properties such that they contain several RNA species and proteins implicated in kidney development, exosomes are putative candidates to serve as developmental programming units in embryonic induction and tissue interactions. We used the mammalian metanephric kidney and its nephron-forming mesenchyme containing the nephron progenitor/stem cells as a model to investigate if secreted exosomes could serve as a novel type of inductive signal in a process defined as embryonic induction that controls organogenesis. As judged by several characteristic criteria, exosomes were enriched and purified from a cell line derived from embryonic kidney ureteric bud (UB) and from primary embryonic kidney UB cells, respectively. The cargo of the UB-derived exosomes was analysed by qPCR and proteomics. Several miRNA species that play a role in Wnt pathways and enrichment of proteins involved in pathways regulating the organization of the extracellular matrix as well as tissue homeostasis were identified. When labelled with fluorescent dyes, the uptake of the exosomes by metanephric mesenchyme (MM) cells and the transfer of their cargo to the cells can be observed. Closer inspection revealed that besides entering the cytoplasm, the exosomes were competent to also reach the nucleus. Furthermore, fluorescently labelled exosomal RNA enters into the cytoplasm of the MM cells. Exposure of the embryonic kidney-derived exosomes to the whole MM in an organ culture setting did not lead to an induction of nephrogenesis but had an impact on the overall organization of the tissue. We conclude that the exosomes provide a novel signalling system with an apparent role in secondary embryonic induction regulating organogenesis.
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http://dx.doi.org/10.1080/20013078.2017.1422675DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5795705PMC
January 2018

Reconstructed Serine 288 in the Left Flipper Region of the Rat P2X7 Receptor Stabilizes Nonsensitized States.

Biochemistry 2017 07 26;56(26):3394-3402. Epub 2017 Jun 26.

A. I. Virtanen Institute, University of Eastern Finland , Kuopio, Finland.

Serine 275, a conserved residue of the left flipper region of ATP-gated P2X3 receptors, plays a key role in both agonist binding and receptor desensitization. It is conserved in most of the P2X receptors except P2X7 and P2X6. By combining experimental patch-clamp and modeling approaches, we explored the role of the corresponding residue in the rat P2X7 receptor (rP2X7) by replacing the phenylalanine at position 288 with serine and characterizing the membrane currents generated by either the wild-type (WT) or the mutated rP2X7 receptor. F288S, an rP2X7 mutation, slowed the deactivation subsequent to 2 and 20 s applications of 1 mM ATP. F288S also prevented sensitization (a progressive current growth) observed with the WT in response to a 20 s application of 1 mM ATP. Increasing the ATP concentration to 5 mM promoted sensitization also in the mutated rP2X7 receptor, accelerating the deactivation rate to typical WT values. YO-PRO1 uptake in cells expressing either the WT or the F288S P2X7 receptor was consistent with recorded membrane current data. Interestingly, in the human P2X7 (hP2X7) receptor, substitution Y288S did not change the deactivation rate, while the Y288F mutant generated a "rat-like" phenotype with a fast deactivation rate. Our combined experimental, kinetic, and molecular modeling data suggest that the rat F288S novel phenotype is due to a slower rate of ATP binding and/or unbinding and stabilization of nonsensitized receptor states.
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http://dx.doi.org/10.1021/acs.biochem.7b00258DOI Listing
July 2017

Selective Calcium-Dependent Inhibition of ATP-Gated P2X3 Receptors by Bisphosphonate-Induced Endogenous ATP Analog ApppI.

J Pharmacol Exp Ther 2017 06 12;361(3):472-481. Epub 2017 Apr 12.

A. I. Virtanen Institute (Y.I., A.Sh., Rai.G., G.B., Ras.G.) and School of Pharmacy (P.T., J. M.), University of Eastern Finland, Kuopio, Finland; Kazan Institute of Biochemistry and Biophysics, Kazan, Russia (A.Sh., A.Sk.); Institute of Biomedicine, University of Turku, Turku, Finland (J.A.M.); and Kazan Federal University, Kazan, Russia (A.Sh., A.Sk., R.Gas.)

Pain is the most unbearable symptom accompanying primary bone cancers and bone metastases. Bone resorptive disorders are often associated with hypercalcemia, contributing to the pathologic process. Nitrogen-containing bisphosphonates (NBPs) are efficiently used to treat bone cancers and metastases. Apart from their toxic effect on cancer cells, NBPs also provide analgesia via poorly understood mechanisms. We previously showed that NBPs, by inhibiting the mevalonate pathway, induced formation of novel ATP analogs such as ApppI [1-adenosin-5'-yl ester 3-(3-methylbut-3-enyl) triphosphoric acid diester], which can potentially be involved in NBP analgesia. In this study, we used the patch-clamp technique to explore the action of ApppI on native ATP-gated P2X receptors in rat sensory neurons and rat and human P2X3, P2X2, and P2X7 receptors expressed in human embryonic kidney cells. We found that although ApppI has weak agonist activity, it is a potent inhibitor of P2X3 receptors operating in the nanomolar range. The inhibitory action of ApppI was completely blocked in hypercalcemia-like conditions and was stronger in human than in rat P2X3 receptors. In contrast, P2X2 and P2X7 receptors were insensitive to ApppI, suggesting a high selectivity of ApppI for the P2X3 receptor subtype. NBP, metabolite isopentenyl pyrophosphate, and endogenous AMP did not exert any inhibitory action, indicating that only intact ApppI has inhibitory activity. Ca-dependent inhibition was stronger in trigeminal neurons preferentially expressing desensitizing P2X3 subunits than in nodose ganglia neurons, which also express nondesensitizing P2X2 subunits. Altogether, we characterized previously unknown purinergic mechanisms of NBP-induced metabolites and suggest ApppI as the endogenous pain inhibitor contributing to cancer treatment with NBPs.
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http://dx.doi.org/10.1124/jpet.116.238840DOI Listing
June 2017

Human Keratinocytes Respond to Extracellular UTP by Induction of Hyaluronan Synthase 2 Expression and Increased Hyaluronan Synthesis.

J Biol Chem 2017 03 10;292(12):4861-4872. Epub 2017 Feb 10.

From the Institute of Biomedicine, University of Eastern Finland, 70211 Kuopio, Finland.

The release of nucleotides into extracellular space is triggered by insults like wounding and ultraviolet radiation, resulting in stimulatory or inhibitory signals via plasma membrane nucleotide receptors. As similar insults are known to activate hyaluronan synthesis we explored the possibility that extracellular UTP or its breakdown products UDP and UMP act as mediators for hyaluronan synthase () activation in human epidermal keratinocytes. UTP increased hyaluronan both in the pericellular matrix and in the culture medium of HaCaT cells. 10-100 μm UTP strongly up-regulated expression, although the other hyaluronan synthases () and hyaluronidases (, ) were not affected. The response was rapid and transient, with the maximum stimulation at 1.5 h. UDP exerted a similar effect, but higher concentrations were required for the response, and UMP showed no stimulation at all. Specific siRNAs against the UTP receptor P2Y, and inhibitors of UDP receptors P2Y and P2Y, indicated that the response to UTP was mediated mainly through P2Y and to a lesser extent via UDP receptors. UTP increased the phosphorylation of p38, ERK, CREB, and Ser-727 of STAT3 and induced nuclear translocation of pCaMKII. Inhibitors of PKC, p38, ERK, CaMKII, STAT3, and CREB partially blocked the activation of expression, confirming the involvement of these pathways in the UTP-induced response. The present data reveal a selective up-regulation of expression by extracellular UTP, which is likely to contribute to the previously reported rapid activation of hyaluronan metabolism in response to tissue trauma or ultraviolet radiation.
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http://dx.doi.org/10.1074/jbc.M116.760322DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5377801PMC
March 2017

Pro-nociceptive migraine mediator CGRP provides neuroprotection of sensory, cortical and cerebellar neurons via multi-kinase signaling.

Cephalalgia 2017 Dec 25;37(14):1373-1383. Epub 2016 Nov 25.

1 Department of Neurobiology, University of Eastern Finland, Kuopio, Finland.

Background Blocking the pro-nociceptive action of CGRP is one of the most promising approaches for migraine prophylaxis. The aim of this study was to explore a role for CGRP as a neuroprotective agent for central and peripheral neurons. Methods The viability of isolated rat trigeminal, cortical and cerebellar neurons was tested by fluorescence vital assay. Engagement of Nrf2 target genes was analyzed by qPCR. The neuroprotective efficacy of CGRP in vivo was tested in mice using a permanent cerebral ischemia model. Results CGRP prevented apoptosis induced by the amino acid homocysteine in all three distinct neuronal populations. Using a set of specific kinase inhibitors, we show the role of multi-kinase signaling pathways involving PKA and CaMKII in neuronal survival. Forskolin triggered a very similar signaling cascade, suggesting that cAMP is the main upstream trigger for multi-kinase neuroprotection. The specific CGRP antagonist BIBN4096 reduced cellular viability, lending further support to the proposed neuroprotective function of CGRP. Importantly, CGRP was neuroprotective against permanent ischemia in mice. Conclusion Our data show an unexpected 'positive' role for the endogenous pro-nociceptive migraine mediator CGRP, suggesting more careful examination of migraine prophylaxis strategy based on CGRP antagonism although it should be noted that homocysteine induced apoptosis in primary neuronal cell culture might not necessarily reproduce all the features of cell loss in the living organism.
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http://dx.doi.org/10.1177/0333102416681588DOI Listing
December 2017

The organic osmolyte betaine induces keratin 2 expression in rat epidermal keratinocytes - A genome-wide study in UVB irradiated organotypic 3D cultures.

Toxicol In Vitro 2015 Dec 25;30(1 Pt B):462-75. Epub 2015 Sep 25.

Institute of Biomedicine, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland.

The moisturizing and potentially protective properties of the organic osmolyte betaine (trimethylglycine) have made it an attractive component for skin care products. Its wide use despite the lack of comprehensive studies addressing its specific effects in skin led us to characterize the molecular targets of betaine in keratinocytes and to explore, whether it modifies the effects of acute UVB exposure. Genome-wide expression analysis was performed on organotypic cultures of rat epidermal keratinocytes, treated either with betaine (10mM), UVB (30 mJ/cm(2)) or their combination. Results were verified with qRT-PCR, western blotting and immunohistochemistry. Additionally, cell proliferation and differentiation were analyzed. Among the 89 genes influenced by betaine, the differentiation marker keratin 2 showed the highest upregulation, which was also confirmed at protein level. Expression of Egr1, a transcription factor, and Purkinje cell protein 4, a regulator of Ca(2+)/calmodulin metabolism, also increased, while downregulated genes included several ion-channel components, such as Fxyd2. Bioinformatics analyses suggest that genes modulated by betaine are involved in DNA replication, might counteract UV-induced processes, and include many targets of transcription factors associated with cell proliferation and differentiation. Our results indicate that betaine controls unique gene expression pathways in keratinocytes, including some involved in differentiation.
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http://dx.doi.org/10.1016/j.tiv.2015.09.015DOI Listing
December 2015

Hyaluronan synthase 3 (HAS3) overexpression downregulates MV3 melanoma cell proliferation, migration and adhesion.

Exp Cell Res 2015 Sep 26;337(1):1-15. Epub 2015 Jul 26.

University of Eastern Finland, Institute of Biomedicine, 70211 Kuopio, Finland.

Malignant skin melanoma is one of the most deadly human cancers. Extracellular matrix (ECM) influences the growth of malignant tumors by modulating tumor cells adhesion and migration. Hyaluronan is an essential component of the ECM, and its amount is altered in many tumors, suggesting an important role for hyaluronan in tumorigenesis. Nonetheless its role in melanomagenesis is not understood. In this study we produced a MV3 melanoma cell line with inducible expression of the hyaluronan synthase 3 (HAS3) and studied its effect on the behavior of the melanoma cells. HAS3 overexpression expanded the cell surface hyaluronan coat and decreased melanoma cell adhesion, migration and proliferation by cell cycle arrest at G1/G0. Melanoma cell migration was restored by removal of cell surface hyaluronan by Streptomyces hyaluronidase and by receptor blocking with hyaluronan oligosaccharides, while the effect on cell proliferation was receptor independent. Overexpression of HAS3 decreased ERK1/2 phosphorylation suggesting that inhibition of MAP-kinase signaling was responsible for these suppressive effects on the malignant phenotype of MV3 melanoma cells.
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http://dx.doi.org/10.1016/j.yexcr.2015.07.026DOI Listing
September 2015

Fluorescence resonance energy transfer (FRET) and proximity ligation assays reveal functionally relevant homo- and heteromeric complexes among hyaluronan synthases HAS1, HAS2, and HAS3.

J Biol Chem 2015 May 20;290(18):11479-90. Epub 2015 Mar 20.

From the Institute of Biomedicine/Anatomy, University of Eastern Finland, FI-70211 Kuopio, Finland,

In vertebrates, hyaluronan is produced in the plasma membrane from cytosolic UDP-sugar substrates by hyaluronan synthase 1-3 (HAS1-3) isoenzymes that transfer N-acetylglucosamine (GlcNAc) and glucuronic acid (GlcUA) in alternative positions in the growing polysaccharide chain during its simultaneous extrusion into the extracellular space. It has been shown that HAS2 immunoprecipitates contain functional HAS2 homomers and also heteromers with HAS3 (Karousou, E., Kamiryo, M., Skandalis, S. S., Ruusala, A., Asteriou, T., Passi, A., Yamashita, H., Hellman, U., Heldin, C. H., and Heldin, P. (2010) The activity of hyaluronan synthase 2 is regulated by dimerization and ubiquitination. J. Biol. Chem. 285, 23647-23654). Here we have systematically screened in live cells, potential interactions among the HAS isoenzymes using fluorescence resonance energy transfer (FRET) and flow cytometric quantification. We show that all HAS isoenzymes form homomeric and also heteromeric complexes with each other. The same complexes were detected both in Golgi apparatus and plasma membrane by using FRET microscopy and the acceptor photobleaching method. Proximity ligation assays with HAS antibodies confirmed the presence of HAS1-HAS2, HAS2-HAS2, and HAS2-HAS3 complexes between endogenously expressed HASs. C-terminal deletions revealed that the enzymes interact mainly via uncharacterized N-terminal 86-amino acid domain(s), but additional binding site(s) probably exist in their C-terminal parts. Of all the homomeric complexes HAS1 had the lowest and HAS3 the highest synthetic activity. Interestingly, HAS1 transfection reduced the synthesis of hyaluronan obtained by HAS2 and HAS3, suggesting functional cooperation between the isoenzymes. These data indicate a general tendency of HAS isoenzymes to form both homomeric and heteromeric complexes with potentially important functional consequences on hyaluronan synthesis.
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http://dx.doi.org/10.1074/jbc.M115.640581DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4416852PMC
May 2015

The role of oxidative stress in degeneration of the neuromuscular junction in amyotrophic lateral sclerosis.

Front Cell Neurosci 2014 13;8:131. Epub 2014 May 13.

Cell Biology Laboratory, Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland Kuopio, Finland ; Laboratory of Neurobiology, Department of Physiology, Kazan Federal University Kazan, Russia.

Amyotrophic lateral sclerosis (ALS) is characterized by the progressive loss of motoneurons and degradation of the neuromuscular junctions (NMJ). Consistent with the dying-back hypothesis of motoneuron degeneration the decline in synaptic function initiates from the presynaptic terminals in ALS. Oxidative stress is a major contributory factor to ALS pathology and affects the presynaptic transmitter releasing machinery. Indeed, in ALS mouse models nerve terminals are sensitive to reactive oxygen species (ROS) suggesting that oxidative stress, along with compromised mitochondria and increased intracellular Ca(2+) amplifies the presynaptic decline in NMJ. This initial dysfunction is followed by a neurodegeneration induced by inflammatory agents and loss of trophic support. To develop effective therapeutic approaches against ALS, it is important to identify the mechanisms underlying the initial pathological events. Given the role of oxidative stress in ALS, targeted antioxidant treatments could be a promising therapeutic approach. However, the complex nature of ALS and failure of monotherapies suggest that an antioxidant therapy should be accompanied by anti-inflammatory interventions to enhance the restoration of the redox balance.
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http://dx.doi.org/10.3389/fncel.2014.00131DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4026683PMC
June 2014

Rab10-mediated endocytosis of the hyaluronan synthase HAS3 regulates hyaluronan synthesis and cell adhesion to collagen.

J Biol Chem 2014 Mar 7;289(12):8375-89. Epub 2014 Feb 7.

From the Institutes of Biomedicine.

Hyaluronan synthases (HAS1-3) are unique in that they are active only when located in the plasma membrane, where they extrude the growing hyaluronan (HA) directly into cell surface and extracellular space. Therefore, traffic of HAS to/from the plasma membrane is crucial for the synthesis of HA. In this study, we have identified Rab10 GTPase as the first protein known to be involved in the control of this traffic. Rab10 colocalized with HAS3 in intracellular vesicular structures and was co-immunoprecipitated with HAS3 from isolated endosomal vesicles. Rab10 silencing increased the plasma membrane residence of HAS3, resulting in a significant increase of HA secretion and an enlarged cell surface HA coat, whereas Rab10 overexpression suppressed HA synthesis. Rab10 silencing blocked the retrograde traffic of HAS3 from the plasma membrane to early endosomes. The cell surface HA coat impaired cell adhesion to type I collagen, as indicated by recovery of adhesion following hyaluronidase treatment. The data indicate a novel function for Rab10 in reducing cell surface HAS3, suppressing HA synthesis, and facilitating cell adhesion to type I collagen. These are processes important in tissue injury, inflammation, and malignant growth.
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http://dx.doi.org/10.1074/jbc.M114.552133DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3961663PMC
March 2014

The role of NMDA and mGluR5 receptors in calcium mobilization and neurotoxicity of homocysteine in trigeminal and cortical neurons and glial cells.

J Neurochem 2014 Apr 4;129(2):264-74. Epub 2013 Dec 4.

Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland; Laboratory of Comparative Physiology of Cerebellum, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Science, Saint-Petersburg, Russia.

Recent studies suggested contribution of homocysteine (HCY) to neurodegenerative disorders and migraine. However, HCY effect in the nociceptive system is essentially unknown. To explore the mechanism of HCY action, we studied short- and long-term effects of this amino acid on rat peripheral and central neurons. HCY induced intracellular Ca²⁺ transients in cultured trigeminal neurons and satellite glial cells (SGC), which were blocked by the NMDA antagonist AP-5 in neurons, but not in SGCs. In contrast, 3-((2-Methyl-4-thiazolyl)ethynyl)pyridine (MTEP), the metabotropic mGluR5 (metabotropic glutamate receptor 5 subtype) antagonist, preferentially inhibited Ca²⁺ transients in SGCs. Prolonged application of HCY induced apoptotic cell death of both kinds of trigeminal cells. The apoptosis was blocked by AP-5 or by the mGluR5 antagonist MTEP. Likewise, in cortical neurons, HCY-induced cell death was inhibited by AP-5 or MTEP. Imaging with 2',7'-dichlorodihydrofluorescein diacetate or mitochondrial dye Rhodamine-123 as well as thiobarbituric acid reactive substances assay did not reveal involvement of oxidative stress in the action of HCY. Thus, elevation of intracellular Ca²⁺ by HCY in neurons is mediated by NMDA and mGluR5 receptors while SGC are activated through the mGluR5 subtype. Long-term neurotoxic effects in peripheral and central neurons involved both receptor types. Our data suggest glutamatergic mechanisms of HCY-induced sensitization and apoptosis of trigeminal nociceptors.
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http://dx.doi.org/10.1111/jnc.12615DOI Listing
April 2014

Hyaluronan production enhances shedding of plasma membrane-derived microvesicles.

Exp Cell Res 2013 Aug 1;319(13):2006-2018. Epub 2013 Jun 1.

Institutes of Biomedicine, Dentistry, and Biocenter Kuopio and Cancer Center of the University of Eastern Finland, P.O.B. 1627, FIN-70211 Kuopio, Finland.

Many cell types secrete plasma membrane-bound microvesicles, suggested to play an important role in tissue morphogenesis, wound healing, and cancer spreading. However, the mechanisms of their formation have remained largely unknown. It was found that the tips of long microvilli induced in cells by overexpression of hyaluronan synthase 3 (HAS3) were detach into the culture medium as microvesicles. Moreover, several cell types with naturally active hyaluronan synthesis released high numbers of plasma membrane-derived vesicles, and inhibition of hyaluronan synthesis reduced their formation. The vesicles contained HAS, and were covered with a thick hyaluronan coat, a part of which was retained even after purification with high-speed centrifugation. HAS3 overexpressing MDCK cells cultured in a 3-D matrix as epithelial cysts released large amounts of HAS- and hyaluronan-positive vesicles from their basal surfaces into the extracellular matrix. As far as we know, hyaluronan synthesis is one of the first molecular mechanisms shown to stimulate the production of microvesicles. The microvesicles have a potential to deliver the hyaluronan synthase machinery and membrane and cytoplasmic materials to other cells, influencing tissue regeneration, inflammation and tumor progression.
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http://dx.doi.org/10.1016/j.yexcr.2013.05.021DOI Listing
August 2013

Low dose ultraviolet B irradiation increases hyaluronan synthesis in epidermal keratinocytes via sequential induction of hyaluronan synthases Has1-3 mediated by p38 and Ca2+/calmodulin-dependent protein kinase II (CaMKII) signaling.

J Biol Chem 2013 Jun 3;288(25):17999-8012. Epub 2013 May 3.

School of Medicine, Institute of Biomedicine/Anatomy, University of Eastern Finland, Kuopio Campus, Yliopistonranta 1 E, P.O. Box 1627, 70211 Kuopio, Finland.

Hyaluronan, a major epidermal extracellular matrix component, responds strongly to different kinds of injuries. This also occurs by UV radiation, but the mechanisms involved are poorly understood. The effects of a single ultraviolet B (UVB) exposure on hyaluronan content and molecular mass, and expression of genes involved in hyaluronan metabolism were defined in monolayer and differentiated, organotypic three-dimensional cultures of rat epidermal keratinocytes. The signals regulating the response were characterized using specific inhibitors and Western blotting. In monolayer cultures, UVB increased hyaluronan synthase Has1 mRNA already 4 h postexposure, with a return to control level by 24 h. In contrast, Has2 and Has3 were persistently elevated from 8 h onward. Silencing of Has2 and especially Has3 decreased the UVB-induced accumulation of hyaluronan. p38 and Ca(2+)/calmodulin-dependent protein kinase II pathways were found to be involved in the UVB-induced up-regulation of Has2 and Has3 expression, respectively, and their inhibition reduced hyaluronan deposition. However, the expressions of the hyaluronan-degrading enzymes Hyal1 and Hyal2 and the hyaluronan receptor Cd44 were also up-regulated by UVB. In organotypic cultures, UVB treatment also resulted in increased expression of both Has and Hyal genes and shifted hyaluronan toward a smaller size range. Histochemical stainings indicated localized losses of hyaluronan in the epidermis. The data show that exposure of keratinocytes to acute, low dose UVB increases hyaluronan synthesis via up-regulation of Has2 and Has3. The simultaneously enhanced catabolism of hyaluronan demonstrates the complexity of the UVB-induced changes. Nevertheless, enhanced hyaluronan metabolism is an important part of the adaptation of keratinocytes to radiation injury.
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http://dx.doi.org/10.1074/jbc.M113.472530DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3689945PMC
June 2013

Hyaluronan in cytosol--microinjection-based probing of its existence and suggested functions.

Glycobiology 2013 Feb 19;23(2):222-31. Epub 2012 Oct 19.

Institute of Biomedicine/Anatomy, School of Medicine, University of Eastern Finland, Kuopio, Finland.

Hyaluronan (HA) is a large glycosaminoglycan produced by hyaluronan synthases (HAS), enzymes normally active at plasma membrane. While HA is delivered into the extracellular space, intracellular HA is also seen, mostly in vesicular structures, but there are also reports on its presence in the cytosol and specific locations and functions there. We probed the possibility of HA localization and functions in cytosol by microinjecting fluorescent HA binding complex (fHABC), HA fragments and hyaluronidase (HYAL) into cytosol. Microinjection of fHABC did not reveal HA-specific intracellular binding sites. Likewise, specific cytosolic binding sites for HA were not detected, as microinjected fluorescent HA composed of 4-8 monosaccharide units (HA4-HA8) were evenly distributed throughout the cells, including the nucleus, but excluded from membrane-bound organelles. The largest HA tested (∼HA120 or ∼25 kDa) did not enter the nucleus, and HA10-HA28 were progressively excluded from parts of nuclei resembling nucleoli. In contrast, HA oligosaccharides endocytosed from medium remained in vesicular compartments. The activity of HA synthesis was estimated by measuring the HA coat on green fluorescent protein (GFP)-HAS3-transfected MCF-7 cells. Microinjection of HA4 reduced coat size at 4 h, but increased at 24 h after injection, while larger HA-oligosaccharides and HYAL had no influence. As a positive control, microinjection of glucose increased coat size. In summary, no evidence for the presence or function of HA in cytosol was obtained. Also, the synthesis of HA and the active site of HAS were not accessible to competition, binding and degradation by cytosolic effectors, while synthesis responded to increased substrate supply.
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http://dx.doi.org/10.1093/glycob/cws149DOI Listing
February 2013

Highly conserved tyrosine 37 stabilizes desensitized states and restricts calcium permeability of ATP-gated P2X3 receptor.

J Neurochem 2011 Nov 10;119(4):676-85. Epub 2011 Oct 10.

Department of Neurobiology, AI Virtanen Institute, University of Eastern Finland, Finland.

Tyrosine 37 in the first transmembrane (TM1) domain is highly conserved in ATP-gated P2X receptors suggesting its fundamental role. We tested whether Y37 contributes to the desensitization of P2X3 receptors, which is currently not well understood. By combining electrophysiological, imaging and modeling approaches, we studied desensitization of various Y37 P2X3 mutants and potential partners of Y37. Unlike the membrane current of the WT receptor, which desensitized in seconds, Y37A mutant current did not fully desensitize even after minutes-long applications of β,γ-meATP, α,β-meATP, ATP or 2MeS-ATP. The fractional calcium current was enhanced in the Y37A mutant. Y37F did not rescue the native P2X3 phenotype indicating a role for the hydroxyl group of Y37 for the WT receptor. Homology modeling indicated I318 or I319 in TM2 as potential partners for Y37 in the receptor closed state. We tested this hypothesis by creating a permanent interaction between the two residues via disulfide bond. Whereas single Y37C, I318C and I319C mutants were functional, the double mutants Y37C-I318C and Y37C-I319C were non-functional. Using a cyclic model of receptor operation, we suggest that the conserved tyrosine 37 links TM1 to TM2 of adjacent subunit to stabilize desensitized states and restricts calcium permeability through the ion channel.
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http://dx.doi.org/10.1111/j.1471-4159.2011.07463.xDOI Listing
November 2011

Selective interference with TRPC3/6 channels disrupts OX1 receptor signalling via NCX and reveals a distinct calcium influx pathway.

Cell Calcium 2010 Aug-Sep;48(2-3):114-23. Epub 2010 Aug 21.

Biomedicum Helsinki, Institute of Biomedicine/Physiology, University of Helsinki, Finland.

TRPC channels play significant roles in the regulation of neuronal plasticity and development. The mechanism by which these nonselective cation channels exert their trophic actions appears to involve entry of Ca(2+) into the cells. Using a neuronal cell model (differentiated human IMR32 neuroblastoma cells), we demonstrate a central role for sodium entry via TRPC3/6 channels in receptor-mediated increases in intracellular calcium. These Na(+)-dependent Ca(2+) influxes, which were observed in a subpopulation of cells, were efficiently blocked by protein kinase C activation, by the Na(+)/Ca(2+) exchanger inhibitors, and by molecular disruption of TRPC3/6 channel function. On the other hand, another subpopulation of cells showed a Na(+)-independent Ca(2+) entry upon stimulation of the same receptors, orexin/hypocretin and bradykinin receptors. This second type of response was not affected by the above mentioned treatments, but it was sensitive to polyvalent cations, such as ruthenium red, spermine and Gd(3+). The data suggest that a NCX-TRPC channel interaction constitutes an important functional unit in receptor-mediated Ca(2+) influx in neuronal cells.
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http://dx.doi.org/10.1016/j.ceca.2010.07.005DOI Listing
June 2011

A role for PKD1 and PKD3 activation in modulation of calcium oscillations induced by orexin receptor 1 stimulation.

Biochim Biophys Acta 2010 Oct 16;1803(10):1206-12. Epub 2010 Jul 16.

Department of Neurobiology, University of Eastern Finland, Kuopio, Finland.

The neuropeptides orexin-A/hypocretin-1 (Ox-A) and orexin-B/hypocretin-2 play an important role in the control of energy metabolism via either of two G-protein-coupled receptors, orexin receptor 1 (Ox1R) and 2. Despite its significant physiological functions, signaling via orexin receptors is still poorly characterized. The aim of this study was to improve our understanding of early signaling events triggered by the binding of Ox-A to Ox1R. Using phosphospecific antibodies, we observed that early kinase activation by Ox-A in a HEK293 cell line stably expressing Ox1R (HEKOx1R) included ERK1/2, PKCdelta, and PKD1. Elevation of intracellular Ca(2+) is a well-characterized response to Ox1R activation. Comparison of Ox-A-induced calcium elevation and PKD1 activation demonstrated that both responses are detectable soon after stimulation and increase in a dose-dependent manner, but inhibition of protein kinase C, when low Ox-A concentrations are used, affects them differently. PKD family of protein kinases has 3 members: PKD1, 2, and 3, which are all expressed in HEKOx1R cells. In response to stimulation of the cells with 1nM Ox-A, both PKD1 and PKD3 are activated and increased in the plasma membrane, pointing at a possible role for these kinases in that cell compartment. Overexpression of either kinase-dead PKD1 or kinase-dead PKD3 disrupts Ox-A-induced calcium oscillations demonstrating the functional role of these kinases in modulating physiological responses to Ox-A.
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http://dx.doi.org/10.1016/j.bbamcr.2010.07.001DOI Listing
October 2010

Differentiation dependent expression of TRPA1 and TRPM8 channels in IMR-32 human neuroblastoma cells.

J Cell Physiol 2009 Oct;221(1):67-74

Biomedicum Helsinki, Institute of Biomedicine/Physiology, University of Helsinki, Helsinki, Finland.

TRPA1 and TRPM8 are transient receptor potential (TRP) channels involved in sensory perception. TRPA1 is a non-selective calcium permeable channel activated by irritants and proalgesic agents. TRPM8 reacts to chemical cooling agents such as menthol. The human neuroblastoma cell line IMR-32 undergoes a remarkable differentiation in response to treatment with 5-bromo-2-deoxyuridine. The cells acquire a neuronal morphology with increased expression of N-type voltage gated calcium channels and neurotransmitters. Here we show using RT-PCR, that mRNA for TRPA1 and TRPM8 are strongly upregulated in differentiating IMR-32 cells. Using whole cell patch clamp recordings, we demonstrate that activators of these channels, wasabi, allyl-isothiocyanate (AITC) and menthol activate membrane currents in differentiated cells. Calcium imaging experiments demonstrated that AITC mediated elevation of intracellular calcium levels were attenuated by ruthenium red, spermine, and HC-030031 as well as by siRNA directed against the channel. This indicates that the detected mRNA level correlate with the presence of functional channels of both types in the membrane of differentiated cells. Although the differentiated IMR-32 cells responded to cooling many of the cells showing this response did not respond to TRPA1/TRPM8 channel activators (60% and 90% for AITC and menthol respectively). Conversely many of the cells responding to these activators did not respond to cooling (30%). This suggests that these channels have also other functions than cold perception in these cells. Furthermore, our results suggest that IMR-32 cells have sensory characteristics and can be used to study native TRPA1 and TRPM8 channel function as well as developmental expression.
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http://dx.doi.org/10.1002/jcp.21828DOI Listing
October 2009

Involvement of TRPC3 channels in calcium oscillations mediated by OX(1) orexin receptors.

Biochem Biophys Res Commun 2009 Jul 21;385(3):408-12. Epub 2009 May 21.

A. I. Virtanen Institute for Molecular Sciences, Department of Neurobiology, University of Kuopio, POB 1627, FI-70211 Kuopio, Finland.

Oscillations of intracellular Ca2+ provide a novel mechanism for sustained activation of cellular processes. Receptor-activated oscillations are mainly thought to occur through rhythmic IP3-dependent store discharge. However, as shown here in HEK293 cells 1 nM orexin-A (Ox-A) acting at OX1 receptors (OX1R) triggered oscillatory Ca2+ responses, requiring external Ca2+. These responses were attenuated by interference with TRPC3 channel (but not TRPC1/4) function using dominant negative constructs, elevated Mg2+ (a blocker of many TRP channels) or inhibition of phospholipase A2. These treatments did not affect Ca2+ oscillations elicited by high concentrations of Ox-A (100 nM) in the absence of external Ca2+. OX1R are thus able to activate TRPC(3)-channel-dependent oscillatory responses independently of store discharge.
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http://dx.doi.org/10.1016/j.bbrc.2009.05.077DOI Listing
July 2009

The orexin OX1 receptor regulates Ca2+ entry via diacylglycerol-activated channels in differentiated neuroblastoma cells.

J Neurosci 2006 Oct;26(42):10658-66

A. I. Virtanen Institute for Molecular Sciences, Department of Neurobiology, University of Kuopio, FIN-70211 Kuopio, Finland.

We studied the cellular response to orexin type 1 receptor (OX1R) stimulation in differentiated IMR-32 neuroblastoma cells. In vitro differentiation of IMR-32 cells with 5-bromo-2'-deoxyuridine leads to a neuronal phenotype with long neurite extensions and an upregulation of mainly N-type voltage-gated calcium channels. Transduction of differentiated IMR-32 cells with baculovirus harboring an OX1R-green fluorescent protein cDNA fusion construct resulted in appearance of fluorescence that was confined mainly to the plasma membrane in the cell body and to neurites. Application of orexin-A to fluorescent cells led to an increase in intracellular free Ca2+ concentration, [Ca2+]i. At low nanomolar concentrations of orexin-A, the response was reversibly attenuated by removal of extracellular Ca2+, by application of a high concentration (10 mM) of Mg2+, and by the pharmacological channel blocker dextromethorphan. A diacylglycerol, dioctanoylglycerol, but not thapsigargin or depolarization with potassium, mimicked the OX1R response with regard to Mg2+ sensitivity. A reverse transcription-PCR screening identified mRNAs for all transient receptor potential canonical (TRPC) channels, including TRPC3, TRPC6, and TRPC7, which are known to be activated by diacylglycerol. Expression of a dominant-negative TRPC6 channel subunit blunted the responses to both dioctanoylglycerol and OX1R stimulation. The results suggest that the OX1R activates a Ca2+ entry pathway that involves diacylglycerol-activated TRPC channels in neuronal cells.
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http://dx.doi.org/10.1523/JNEUROSCI.2609-06.2006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6674737PMC
October 2006

Agonist potency differentiates G protein activation and Ca2+ signalling by the orexin receptor type 1.

Biochem Pharmacol 2006 Mar 20;71(6):827-36. Epub 2006 Jan 20.

A.I. Virtanen Institute for Molecular Sciences, University of Kuopio, FIN-70211 Kuopio, Finland.

The G protein coupling characteristics of a flag epitope-tagged orexin receptor type 1 (OX1R) was investigated in HEK293 cells. Immunoprecipitation of the OX1R and immunoblotting revealed interactions with Gq/G11 proteins as well as with Gs and Gi proteins. Stimulation with orexin-A did not affect the ability of the OX1R to coprecipitate Gq/G11 proteins, but it robustly elevated the intracellular concentration of Ca2+, [Ca2+]i. No changes in cAMP levels could be detected upon receptor stimulation. To get further insight into the functional correlation of G protein activation and Ca2+ signalling, we used baculovirus transduction to express chimeric G proteins, containing the Galphas protein backbone with various Galpha donor sequences (Galphas/x) at the N and C termini, and measured cAMP as functional output. The Galphas/x chimeric proteins with Galpha11(Galphaq) and Galpha16 structure in the C terminus were stimulated by the OX1R. Concentration-response curves with Galphas/16 revealed an agonist potency correlation between G protein activation and the elevation of [Ca2+]i via discharge of intracellular Ca2+ stores, a feature also recognized for the muscarinic M3 receptor. However, in contrast to the M3 receptor, the OX1R elevated [Ca2+]i via influx from extracellular space at about 30-fold lower agonist concentration. The results suggest that the OX1R is linked to influx of Ca2+ through a signal pathway independent of Gq/G11 protein activation.
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http://dx.doi.org/10.1016/j.bcp.2005.12.021DOI Listing
March 2006

Orexin-A-induced Ca2+ entry: evidence for involvement of trpc channels and protein kinase C regulation.

J Biol Chem 2005 Jan 10;280(3):1771-81. Epub 2004 Nov 10.

A. I. Virtanen Institute for Molecular Sciences, Department of Neurobiology, Laboratory of Cell Biology, University of Kuopio, P. O. Box 1627, FIN-70211 Kuopio, Finland.

The orexins are peptide transmitters/hormones, which exert stimulatory actions in many types of cells via the G-protein-coupled OX(1) and OX(2) receptors. Our previous results have suggested that low (subnanomolar) concentrations of orexin-A activate Ca(2+) entry, whereas higher concentrations activate phospholipase C, Ca(2+) release, and capacitative Ca(2+) entry. As shown here, the Ca(2+) response to subnanomolar orexin-A concentrations was blocked by activation of protein kinase C by using different approaches (12-O-tetradecanoylphorbol acetate, dioctanoylglycerol, and diacylglycerol kinase inhibition) and protein phosphatase inhibition by calyculin A. The Ca(2+) response to subnanomolar orexin-A concentrations was also blocked by Mg(2+), dextromethorphan, and tetraethylammonium. These treatments neither affected the response to high concentrations of orexin-A nor the thapsigargin-stimulated capacitative entry. The capacitative entry was instead strongly suppressed by SKF96365. An inward membrane current activated by subnanomolar concentrations of orexin-A and the currents activated upon transient expression of trpc3 channels were also sensitive to Mg(2+), dextromethorphan, and tetraethylammonium. Responses to subnanomolar concentrations of orexin-A (Ca(2+) elevation, inward current, and membrane depolarization) were voltage-dependent with a loss of the response around -15 mV. By using reverse transcription-PCR, mRNA for the trpc1-4 channel isoforms were detected in the CHO-hOX1-C1 cells. The expression of truncated TRPC channel isoforms, in particular trpc1 and trpc3, reduced the response to subnanomolar concentrations of orexin-A but did not affect the response to higher concentrations of orexin-A. The results suggest that activation of the OX(1) receptor leads to opening of a Ca(2+)-permeable channel, involving trpc1 and -3, which is controlled by protein kinase C.
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http://dx.doi.org/10.1074/jbc.M406073200DOI Listing
January 2005
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