Publications by authors named "John J Siekierka"

9 Publications

  • Page 1 of 1

Discovery of isoxazolyl-based inhibitors of cGMP-dependent protein kinase.

RSC Med Chem 2020 Jan 16;11(1):98-101. Epub 2019 Dec 16.

Department of Chemistry and Biochemistry , Montclair State University , Montclair , NJ 07043 , USA . Email:

The cGMP-dependent protein kinase in (PfPKG) plays multiple roles in the life cycle of the parasite. As a result, this enzyme is a potential target for new antimalarial agents. Existing inhbitors, while potent and active in malaria models are not optimal. This communication describes initial optimization of a structurally distinct class of PfPKG inhibitors.
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http://dx.doi.org/10.1039/c9md00511kDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7536641PMC
January 2020

Discovery of a Stress-Activated Protein Kinase Inhibitor for Lymphatic Filariasis.

ACS Med Chem Lett 2018 Mar 9;9(3):210-214. Epub 2018 Feb 9.

Sokol Institute for Pharmaceutical Life Sciences and Department of Chemistry and Biochemistry, Montclair State University, Montclair, New Jersey 07043, United States.

Lymphatic filariasis infects over 120 million people worldwide and can lead to significant disfigurement and disease. Resistance is emerging with current treatments, and these therapies have dose limiting adverse events; consequently new targets are needed. One approach to achieve this goal is inhibition of parasitic protein kinases involved in circumventing host defense mechanisms. This report describes structure-activity relationships leading to the identification of a potent, orally bioavailable stress activated protein kinase inhibitor that may be used to investigate this hypothesis.
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http://dx.doi.org/10.1021/acsmedchemlett.7b00477DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5846038PMC
March 2018

Expression, purification and enzymatic characterization of Brugia malayi dihydrofolate reductase.

Protein Expr Purif 2016 12 18;128:81-5. Epub 2016 Aug 18.

Department of Chemistry and Biochemistry, Montclair State University, 1 Normal Avenue, Montclair, NJ, 07043, USA. Electronic address:

Brugia malayi (B. malayi) is one of the three causative agents of lymphatic filariasis, a neglected parasitic disease. Current literature suggests that dihydrofolate reductase is a potential drug target for the elimination of B. malayi. Here we report the recombinant expression and purification of a ∼20 kDa B. malayi dihydrofolate reductase (BmDHFR). A His6-tagged construct was expressed in E. coli and purified by affinity chromatography to yield active and homogeneous enzyme for steady-state kinetic characterization and inhibition studies. The catalytic activity kcat was found to be 1.4 ± 0.1 s(-1), the Michaelis Menten constant KM for dihydrofolate 14.7 ± 3.6 μM, and the equilibrium dissociation constant KD for NADPH 25 ± 24 nM. For BmDHFR, IC50 values for a six DHFR inhibitors were determined to be 3.1 ± 0.2 nM for methotrexate, 32 ± 22 μM for trimethoprim, 109 ± 34 μM for pyrimethamine, 154 ± 46 μM for 2,4-diaminoquinazoline, 771 ± 44 μM for cycloguanil, and >20,000 μM for 2,4-diaminopyrimidine. Our findings suggest that antifolate compounds can serve as inhibitors of BmDHFR.
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http://dx.doi.org/10.1016/j.pep.2016.08.012DOI Listing
December 2016

Human p38 mitogen-activated protein kinase inhibitor drugs inhibit Plasmodium falciparum replication.

Exp Parasitol 2011 Jun 19;128(2):170-5. Epub 2011 Feb 19.

Cancer Therapy & Research Center, University of Texas Health Science Center at San Antonio, 2040 Babcock Rd., Suite 201, San Antonio, TX 78229, USA.

We recently demonstrated that human p38 mitogen-activated protein kinase (MAPK) inhibitors reduced in vitro and in vivo replication of the protozoan parasites Toxoplasma gondii and Encephalitozoon cuniculi. In this study, we assessed the efficacy of five p38 MAPK inhibitors to block the replication of Plasmodium falciparum in human erythrocytes cultured ex vivo and demonstrate that the pyridinylimidazole RWJ67657 and the pyrrolobenzimidazole RWJ68198 reduced P. falciparum replication, yielded trophozoites that were greatly diminished in size at 24h, and that these two agents interfered with stage differentiation. Interestingly, the chloroquine-resistant strain W2 was significantly more sensitive to these drugs than was the chloroquine-sensitive strain HB3. These results suggest that pyridinylimidazoles and pyrrolobenzimidazoles designed to inhibit human p38 MAPK activation can be developed to treat malaria.
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http://dx.doi.org/10.1016/j.exppara.2011.02.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3076546PMC
June 2011

The role of a Brugia malayi p38 MAP kinase ortholog (Bm-MPK1) in parasite anti-oxidative stress responses.

Mol Biochem Parasitol 2011 Apr 24;176(2):90-7. Epub 2010 Dec 24.

Department of Chemistry and Biochemistry and The Herman and Margaret Sokol Institute for Pharmaceutical Life Sciences, Montclair State University, Montclair, NJ 07043, USA.

Filariasis, caused by thread-like nematode worms, affects millions of individuals throughout the tropics and is a major cause of acute and chronic morbidity. Filarial nematodes effectively evade host immunological responses and are long lived within their hosts. Recently an emphasis has been placed on enzymatic and non-enzymatic anti-oxidant systems which counteract the generation of reactive oxygen species (ROS) by macrophages and granulocytes, a first line of defense against parasites. We have characterized an anti-oxidant pathway in the filarial parasite Brugia malayi related to the evolutionarily conserved human mitogen-activated p38 protein kinase and the Caenorhabditis elegans PMK-1 protein kinase stress pathways. We have expressed a recombinant p38/PMK-1 ortholog from B. malayi (Bm-MPK1) and have successfully activated the kinase with mammalian upstream kinases. In addition, we have demonstrated inhibition of Bm-MPK1 activity using a panel of known p38 inhibitors. Using the potent and highly selective allosteric p38 inhibitor, BIRB796, we have implicated Bm-MPK1 in a pathway which offers B. malayi protection from the effects of ROS. Our results, for the first time, describe a stress-activated protein kinase pathway within the filarial parasite B. malayi which plays a role in protecting the parasite from ROS. Inhibition of this pathway may have therapeutic benefit in treating filariasis by increasing the sensitivity of filarial parasites to ROS and other reactive intermediates.
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http://dx.doi.org/10.1016/j.molbiopara.2010.12.008DOI Listing
April 2011

Apicomplexa, trypanosoma and parasitic nematode protein kinases as antiparasitic therapeutic targets.

Curr Opin Investig Drugs 2010 Feb;11(2):147-56

Montclair State University, Sokol Institute of Pharmaceutical Life Sciences and Department of Chemistry and Biochemistry, 1 Normal Avenue, Montclair, NJ 07043, USA.

Parasitic infections caused by Plasmodium, Trypanosoma, Leishmania, Toxoplasma and parasitic nematodes affect hundreds of millions of individuals worldwide and are the cause of significant mortality and morbidity, particularly in developing countries. These diseases also have an impact on individuals from developed countries; for example, some US troops in Iraq and Afghanistan have been infected with Leishmania. The annual mortality associated with parasitic infections is estimated to be 1.5 million deaths. The socioeconomic impact of the morbidity associated with parasitic infections is significant, and the development of new drugs, aimed at novel targets, is urgently needed to develop effective treatments for these diseases. The small-molecule inhibitors discussed in this review constitute useful tools with which to explore the relevance of kinase inhibition in inducing antiparasitic activity. The aim of recent target-based approaches used in the development of parasite kinase inhibitors is to identify novel antiparasitic agents with therapeutic potential.
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February 2010

HIV-1 Nef-induced FasL induction and bystander killing requires p38 MAPK activation.

Blood 2005 Sep 31;106(6):2059-68. Epub 2005 May 31.

University of Pennsylvania School of Medicine, Department of Pathology & Laboratory Medicine 422 Curie Blvd, Philadelphia, PA 19104, USA.

The human immunodeficiency virus (HIV) has been reported to target noninfected CD4 and CD8 cells for destruction. This effect is manifested in part through up-regulation of the death receptor Fas ligand (FasL) by HIV-1 negative factor (Nef), leading to bystander damage. However, the signal transduction and transcriptional regulation of this process remains elusive. Here, we provide evidence that p38 mitogen-activated protein kinase (MAPK) is required for this process. Loss-of-function experiments through dominant-negative p38 isoform, p38 siRNA, and chemical inhibitors of p38 activation suggest that p38 is necessary for Nef-induced activator protein-1 (AP-1) activation, as inhibition leads to an attenuation of AP-1-dependent transcription. Furthermore, mutagenesis of the FasL promoter reveals that its AP-1 enhancer element is required for Nef-mediated transcriptional activation. Therefore, a linear pathway for Nef-induced FasL expression that encompasses p38 and AP-1 has been elucidated. Furthermore, chemical inhibition of the p38 pathway attenuates HIV-1-mediated bystander killing of CD8 cells in vitro.
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http://dx.doi.org/10.1182/blood-2005-03-0932DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1895138PMC
September 2005

Suppression of HIV-1 viral replication and cellular pathogenesis by a novel p38/JNK kinase inhibitor.

AIDS 2004 Mar;18(5):739-48

Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.

Objective: To analyze a novel compound, which inhibits serine-threonine protein kinase p38, for its possible bioactivity against HIV-1 infection.

Methods: Proteins involved in cellular signal transduction pathways represent a novel class of host therapeutic targets for infectious diseases. In this regard the serine/threonine kinase p38 MAPK, a member of the mitogen-activated protein (MAP) kinase superfamily of signal transduction molecules may play an important role in HIV-1 infection. We analyzed the ability of this compound (RWJ67657) to inhibit HIV replication in primary T cells and monocytes. Cellular expression of phospho-p38MAPK was studied by Western blot analysis. Blockade of HIV infection induced apoptosis was measured by Annexin V staining.

Results: p38 inhibitor RWJ67657 was effective in inhibiting HIV-1 replication in both T-cell and monocyte cell lines, irrespective of the coreceptor used by the virus for entry into the cell. Importantly, both reverse transcriptase and protease resistant escape mutant viruses were effectively suppressed by RWJ67657. In addition, the tested compounds block HIV-induced T-cell apoptosis, a critical means of T-cell depletion linked to AIDS progression.

Conclusion: Several steps in the HIV-1 virus life cycle appear to depend on cellular activation, including activation of the p38 pathway. Without activation virus replication is thought to be blocked due to incomplete reverse transcription and a lack of proviral DNA integration. The data collectively illustrate that inhibition of the p38 pathway can affect HIV-1 replication. Interruption of HIV infection by p38 inhibitors underscores the value of exploring antiviral drugs that target host cellular proteins.
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http://dx.doi.org/10.1097/00002030-200403260-00004DOI Listing
March 2004

Imidazopyrimidines, potent inhibitors of p38 MAP kinase.

Bioorg Med Chem Lett 2003 Feb;13(3):347-50

Drug Discovery, Johnson & Johnson Pharmaceutical Research and Development, L.L.C., 1000 Route 202, Raritan, NJ 08869, USA.

The MAP kinase p38 is implicated in the release of the pro-inflammatory cytokines TNF-alpha and IL-1 beta. Inhibition of cytokine release may be a useful treatment for inflammatory conditions such as rheumatoid arthritis and Crohn's disease. A novel series of imidazopyrimidines have been discovered that potently inhibit p38 and suppress the production of TNF-alpha in vivo.
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http://dx.doi.org/10.1016/s0960-894x(02)01020-xDOI Listing
February 2003