Gnidimacrin, a Potent Anti-HIV Diterpene, Can Eliminate Latent HIV-1 Ex Vivo by Activation of Protein Kinase C β

An effective means to eradicate latent reservoirs in HIV-1-infected individuals remains elusive. Attempts to purge these reservoirs were undertaken over a decade ago without success. The subsequent lapse in further clinical attempts since may have been justified as our knowledge of the mechanisms which underpin the latent state still evolves. Although additional novel molecular antagonists of HIV-1 latency have subsequently been reported, these candidate agents have not been tested in human trials for reservoir ablation. This review provides an overview of the protein kinase C (PKC) pathway which can be modulated by small molecular agents to induce the expression of latent HIV-1 from within infected reservoir cells. Some of these agents have been tested against select cancers with seemingly tolerable side effects. As such, modulation of the PKC pathway may yet be a viable mechanism toward HIV-1 reservoir eradication.

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Activation of Latent HIV-1 Expression by Protein Kinase C Agonists. A Novel Therapeutic Approach to Eradicate HIV-1 Reservoirs

Current Drug Targets ◽

10.2174/138945011794815266 ◽

2011 ◽

Vol 12 (3) ◽

pp. 348-356 ◽

Cited By ~ 31

Author(s):

Gonzalo Sanchez-Duffhues ◽

Minh Q. Vo ◽

Moises Perez ◽

Marco A. Calzado ◽

Santiago Moreno ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Therapeutic Approach ◽

Kinase C ◽

Latent Hiv ◽

Hiv 1 ◽

Novel Therapeutic

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Ex VivoBioactivity and HIV-1 Latency Reversal by Ingenol Dibenzoate and Panobinostat in Resting CD4+T Cells from Aviremic Patients

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01077-15 ◽

2015 ◽

Vol 59 (10) ◽

pp. 5984-5991 ◽

Cited By ~ 53

Author(s):

Adam M. Spivak ◽

Alberto Bosque ◽

Alfred H. Balch ◽

David Smyth ◽

Laura Martins ◽

...

Keyword(s):

T Cells ◽

Protein Kinase C ◽

Protein Kinase ◽

Ex Vivo ◽

Viral Reactivation ◽

Major Barrier ◽

Kinase C ◽

Wide Range ◽

Hiv 1 ◽

In Cells

ABSTRACTThe human immunodeficiency virus type 1 (HIV-1) latent reservoir in resting CD4+T cells represents a major barrier to viral eradication. Small compounds capable of latency reversal have not demonstrated uniform responses acrossin vitroHIV-1 latency cell models. Characterizing compounds that demonstrate latency-reversing activity in resting CD4+T cells from aviremic patientsex vivowill help inform pilot clinical trials aimed at HIV-1 eradication. We have optimized a rapidex vivoassay using resting CD4+T cells from aviremic HIV-1+patients to evaluate both the bioactivity and latency-reversing potential of candidate latency-reversing agents (LRAs). Using this assay, we characterize the properties of two candidate compounds from promising LRA classes, ingenol 3,20-dibenzoate (a protein kinase C agonist) and panobinostat (a histone deacetylase inhibitor), in cells from HIV-1+antiretroviral therapy (ART)-treated aviremic participants, including the effects on cellular activation and cytotoxicity. Ingenol induced viral release at levels similar to those of the positive control (CD3/28 receptor stimulation) in cells from a majority of participants and represents an exciting LRA candidate, as it combines a robust viral reactivation potential with a low toxicity profile. At concentrations that blocked histone deacetylation, panobinostat displayed a wide range of potency among participant samples and consistently induced significant levels of apoptosis. The protein kinase C agonist ingenol 3,20-dibenzoate demonstrated significant promise in a rapidex vivoassay using resting CD4+T cells from treated HIV-1-positive patients to measure latent HIV-1 reactivation.

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Differential Regulation of Myosin Regulatory Light Chain Phosphorylation by Protein Kinase C Isozymes in Human Uterine Myocytes

Reproductive Sciences ◽

10.1177/1933719118802062 ◽

2018 ◽

Vol 26 (7) ◽

pp. 988-996

Author(s):

Bryan F. Mitchell ◽

Mei Chi ◽

Elle Surgent ◽

Bailey M. Sorochan ◽

Curtis N. Tracey ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Light Chain ◽

Myosin Light Chain ◽

Ex Vivo ◽

Neonatal Morbidity ◽

The Novel ◽

Uterine Contractility ◽

Uterine Activity ◽

Kinase C

Background: Preterm birth is the most common cause of neonatal morbidity and mortality and a common precedent to lifelong disability. Current treatment has minimal efficacy. Objective: We assessed the role of isozymes of the protein kinase C (PKC) family in regulating the phosphorylation of myosin regulatory light chains (RLCs), which regulate uterine contractility. We also explored the mechanisms through which these isozymes function. Study Design: We used a previously characterized and validated quantitative in-cell Western (ICW) assay to measure site-specific phosphorylations on myosin RLC and CPI-17. Cultures of human uterine myocytes (hUM) were treated with the potent contractile stimulant oxytocin to induce uterine contractility or a pharmacological mimic of diacyl-glycerol to stimulate the conventional and novel isozymes of the PKC family. Combinations of isozyme-selective inhibitors were used to determine the effects of the conventional and novel classes of isozymes. Results: Stimulation of PKC using phospho-dibutyrate caused immediate, concentration-dependent inhibition of uterine activity ex vivo. Using the ICW assay with hUM, the oxytocin-stimulated increase in the pro-contractile phosphorylations of myosin RLCs at serine19 and threonine18 was completely inhibited by prior treatment with phorbol-12-myristate-13-acetate, which stimulates both convention and novel classes of isozymes. Our results suggest that the conventional class of isozymes cause a reduction in phosphorylations at serine19 and threonine18 by reducing activity of myosin light chain kinase. The novel class of isozymes has 2 mechanisms of action: the first is activation of CPI-17 through phosphorylation at threonine38, which results in reduced activity of myosin light chain phosphatase and increased levels of activated myosin RLC; the second is increased phosphorylation of the N-terminal region of myosin RLC. Conclusions: Specific agonists for the conventional isozymes or inhibitors of the novel isozymes of the PKC family could be useful pharmacological agents for regulation of uterine activity.

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Involvement of Protein Kinase C in HIV-1 gp120-Induced Apoptosis in Primary Endothelium

JAIDS Journal of Acquired Immune Deficiency Syndromes ◽

10.1097/00126334-200012150-00001 ◽

2000 ◽

Vol 25 (5) ◽

pp. 375-389 ◽

Cited By ~ 19

Author(s):

Ming-Bo Huang ◽

Vincent C. Bond

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Kinase C ◽

Induced Apoptosis ◽

Hiv 1

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Biogenesis of P-TEFb in CD4+ T cells to reverse HIV latency is mediated by protein kinase C (PKC)-independent signaling pathways

10.1101/2021.04.26.441433 ◽

2021 ◽

Author(s):

Uri Mbonye ◽

Konstantin Leskov ◽

Meenakshi Shukla ◽

Saba Valadkhan ◽

Jonathan Karn

Keyword(s):

T Cells ◽

Protein Kinase C ◽

T Cell ◽

Protein Kinase ◽

Signaling Pathways ◽

Cd4 T Cells ◽

Hiv Latency ◽

Kinase C ◽

Latent Hiv ◽

Memory Cd4 T Cells

The switch between HIV latency and productive transcription is regulated by an auto-feedback mechanism initiated by the viral trans-activator Tat, which functions to recruit the host transcription elongation factor P-TEFb to proviral HIV. A heterodimeric complex of CDK9 and one of three cyclin T subunits, P-TEFb is expressed at vanishingly low levels in resting memory CD4 + T cells and cellular mechanisms controlling its availability are central to regulation of the emergence of HIV from latency. Using a well-characterized primary T-cell model of HIV latency alongside healthy donor memory CD4 + T cells, we characterized specific T-cell receptor (TCR) signaling pathways that regulate the generation of transcriptionally active P-TEFb, defined as the coordinate expression of cyclin T1 and phospho-Ser175 CDK9. Protein kinase C (PKC) agonists, such as ingenol and prostratin, stimulated active P-TEFb expression and reactivated latent HIV with minimal cytotoxicity, even in the absence of intracellular calcium mobilization with an ionophore. Unexpectedly, inhibition-based experiments demonstrated that PKC agonists and TCR-mobilized diacylglycerol signal through MAP kinases ERK1/2 rather than through PKC to effect the reactivation of both P-TEFb and latent HIV. Single-cell and bulk RNA-seq analyses revealed that of the four known isoforms of the Ras guanine nucleotide exchange factor RasGRP, RasGRP1 is by far the predominantly expressed diacylglycerol-dependent isoform in CD4 + T cells. RasGRP1 should therefore mediate the activation of ERK1/2 via Ras-Raf signaling upon TCR co-stimulation or PKC agonist challenge. Combined inhibition of the PI3K-mTORC2-AKT-mTORC1 pathway and the ERK1/2 activator MEK prior to TCR co-stimulation abrogated active P-TEFb expression and substantially suppressed latent HIV reactivation. Therefore, contrary to prevailing models, the coordinate reactivation of P-TEFb and latent HIV in primary T cells following either TCR co-stimulation or PKC agonist challenge is independent of PKC but rather involves two complementary signaling arms of the TCR cascade, namely, RasGRP1-Ras-Raf-MEK-ERK1/2 and PI3K-mTORC2-AKT-mTORC1.

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Insulin generates free radicals in human fibroblasts ex vivo by a protein kinase C-dependent mechanism, which is inhibited by pravastatin

Free Radical Biology and Medicine ◽

10.1016/j.freeradbiomed.2006.04.015 ◽

2006 ◽

Vol 41 (3) ◽

pp. 473-483 ◽

Cited By ~ 16

Author(s):

G CEOLOTTO ◽

I PAPPARELLA ◽

L LENZINI ◽

M SARTORI ◽

M MAZZONI ◽

...

Keyword(s):

Protein Kinase C ◽

Free Radicals ◽

Protein Kinase ◽

Ex Vivo ◽

Human Fibroblasts ◽

Kinase C ◽

Dependent Mechanism

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Identification of Combinations of Protein Kinase C Activators and Histone Deacetylase Inhibitors that Potently Reactivate Latent HIV

Viruses ◽

10.3390/v12060609 ◽

2020 ◽

Vol 12 (6) ◽

pp. 609

Author(s):

Francesca Curreli ◽

Shahad Ahmed ◽

Sofia M. Benedict Victor ◽

Asim K. Debnath

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Synergistic Effect ◽

Histone Deacetylase ◽

Histone Deacetylase Inhibitors ◽

Latent Virus ◽

Hiv Latency ◽

Kinase C ◽

Protein Kinase C Activators ◽

Latent Hiv

Combination antiretroviral therapy (cART) is successful in maintaining undetectable levels of HIV in the blood; however, the persistence of latent HIV reservoirs has become the major barrier for a HIV cure. Substantial efforts are underway in finding the best latency-reversing agents (LRAs) to purge the latent viruses from the reservoirs. We hypothesize that identifying the right combination of LRAs will be the key to accomplishing that goal. In this study, we evaluated the effect of combinations of three protein kinase C activators (prostratin, (-)-indolactam V, and TPPB) with four histone deacetylase inhibitors (AR-42, PCI-24781, givinostat, and belinostat) on reversing HIV latency in different cell lines including in a primary CD4+ T-cell model. Combinations including indolactam and TPPB with AR-42 and PCI produced a strong synergistic effect in reactivating latent virus as indicated by higher p24 production and envelope gp120 expression. Furthermore, treatment with TPPB and indolactam greatly downregulated the cellular receptor CD4. Indolactam/AR-42 combination emerged from this study as the best combination that showed a strong synergistic effect in reactivating latent virus. Although AR-42 alone did not downregulate CD4 expression, indolactam/AR-42 showed the most efficient downregulation. Our results suggest that indolactam/AR-42 is the most effective combination, showing a strong synergistic effect in reversing HIV latency combined with the most efficient CD4 downregulation.

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ChemInform Abstract: 12-O-Acetylphorbol-13-decanoate Potently Inhibits Cytopathic Effects of Human Immunodeficiency Virus Type 1 (HIV-1), without Activation of Protein Kinase C.

ChemInform ◽

10.1002/chin.200011179 ◽

2010 ◽

Vol 31 (11) ◽

pp. no-no

Author(s):

Sahar El-Mekkawy ◽

Meselhy R. Meselhy ◽

Norio Nakamura ◽

Masao Hattori ◽

Takuya Kawahata ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Protein Kinase C ◽

Protein Kinase ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Cytopathic Effects ◽

Kinase C ◽

Immunodeficiency Virus ◽

Hiv 1

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Cigarette smoke extract induces endothelin-1 via protein kinase C in pulmonary artery endothelial cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.2001.281.2.l403 ◽

2001 ◽

Vol 281 (2) ◽

pp. L403-L411 ◽

Cited By ~ 18

Author(s):

Sang-Do Lee ◽

Dong-Soon Lee ◽

Yong-Gam Chun ◽

Tae-Sun Shim ◽

Chae-Man Lim ◽

...

Keyword(s):

Gene Expression ◽

Endothelial Cells ◽

Protein Kinase C ◽

Protein Kinase ◽

Pulmonary Artery ◽

Cigarette Smoke ◽

De Novo ◽

Ex Vivo ◽

Cigarette Smoke Extract ◽

Kinase C

We examined the mechanism of endothelin (ET)-1 regulation by cigarette smoke extract (CSE) and the effect of platelets on CSE-induced stimulation of ET-1 gene expression in human and bovine pulmonary artery endothelial cells (PAECs). Our data show that CSE (1%) induces ET-1 gene expression (after 1 h) and ET-1 peptide synthesis (after 4 h) in bovine PAECs. The induction of preproET-1 mRNA level was due to de novo transcription, and new protein synthesis was not required for this induction. The protein kinase C inhibitors staurosporine (10−8mol/l) and calphostin C (10−7mol/l) abolished the induction of ET-1 gene expression by CSE in bovine and human PAECs. Although a lower concentration of platelets (106cells/ml in bovine PAECs; 107cells/ml in human PAECs) did not significantly alter ET-1 gene expression in PAECs, incubation of platelets with CSE (1%) and PAECs produced a significant increase in preproET-1 mRNA and ET-1 peptide compared with the values in the presence of CSE (1%) alone. CSE (1%) induced platelet aggregation and increased the expression of platelet membrane glycoproteins ex vivo. Thus our data suggest that CSE stimulates ET-1 gene expression via PKC in PAECs. CSE and platelets showed a synergistic effect on ET-1 gene expression, possibly through the activation of platelets by CSE.

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