Protein Kinase C δ Regulates the Depletion of Actin at the Immunological Synapse Required for Polarized Exosome Secretion by T Cells

ABSTRACT CARMA1 (also known as CARD11) is a scaffold molecule and contains a caspase-recruitment domain (CARD) and a membrane-associated guanylate kinase-like (MAGUK) domain. It plays an essential role in mediating CD3/CD28 costimulation-induced NF-κB activation. However, the molecular mechanism by which CARMA1 mediates costimulatory signals remains to be determined. Here, we show that CARMA1 is constitutively associated with the cytoplasmic membrane. This membrane association is essential for the function of CARMA1, since a mutant of CARMA1, CARMA1(L808P), that is defective in the membrane association cannot rescue CD3/CD28 costimulation-induced NF-κB activation in JPM50.6 CARMA1-deficient T cells. Although CD3/CD28 costimulation effectively induces the formation of the immunological synapse in CARMA1-deficient T cells, the recruitment of protein kinase C-θ (PKC-θ), Bcl10, and IκB kinase β (IKKβ) into lipid rafts of the immunological synapse is defective. Moreover, expression of wild-type CARMA1, but not CARMA1(L808P), restores the recruitment of PKC-θ, Bcl10, and IKKβ into lipid rafts in CARMA1-deficient T cells. Consistently, expression of a mutant CARMA1, CARMA1(ΔCD), that cannot associate with Bcl10 failed to restore CD3/CD28 costimulation-induced NF-κB activation in JPM50.6 cells, whereas expression of Bcl10-CARMA(ΔCD) fusion protein effectively restored this NF-κB activation. Together, these results indicate that CARMA1 mediates CD3/CD28 costimulation-induced NF-κB activation by recruiting downstream signaling components into the immunological synapse.

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Differential Requirements for Protein Kinase C-Theta at The Immunological Synapse of Effector Versus Regulatory T Cells and Their Clinical Implications

Journal of Clinical & Cellular Immunology ◽

10.4172/2155-9899.1000e104 ◽

2012 ◽

Vol 03 (01) ◽

Keyword(s):

T Cells ◽

Protein Kinase C ◽

Protein Kinase ◽

Regulatory T Cells ◽

Immunological Synapse ◽

Clinical Implications ◽

Kinase C

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Protein Kinase C-Theta (PKCθ): A Rheostat in T cell Signaling and Cancer

Journal of Clinical & Experimental Immunology ◽

10.33140/jcei/01/02/00001 ◽

2016 ◽

Vol 1 (2) ◽

Keyword(s):

Signal Transduction ◽

T Cells ◽

Protein Kinase C ◽

T Cell ◽

Protein Kinase ◽

Cell Signaling ◽

Immunological Synapse ◽

Signal Transduction Pathway ◽

T Cell Signaling ◽

Kinase C

Protein kinase C-theta (PKCθ) is a key enzyme in T lymphocytes signal transduction pathway that works downstream of the activated T cell receptor (TCR) and the CD28 receptor. This protein translocates to the center of the immunological synapse (IS) as T cells encounter an antigen. Depending on the quality and quantity of extracellular antigenic stimuli, PKCθ differentially phosphorylates and activates different effector molecules that mediate signal transduction into distinct subcellular compartments and activate the major T cell responsive transcription factors, NF-κB, NFAT and AP-1. Besides having a major biological role in T cells, PKCθ is also expressed at high levels in gastrointestinal stromal tumors, although the functional importance is not fully clear. The present manuscript shades light on the current understanding on PKCθ in T cell signaling and cancer.

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Protein Kinase C θ Affects Ca2+ Mobilization and NFAT Activation in Primary Mouse T Cells

Journal of Experimental Medicine ◽

10.1084/jem.20020234 ◽

2003 ◽

Vol 197 (11) ◽

pp. 1525-1535 ◽

Cited By ~ 231

Author(s):

Christa Pfeifhofer ◽

Kurt Kofler ◽

Thomas Gruber ◽

Nassim Ghaffari Tabrizi ◽

Christina Lutz ◽

...

Keyword(s):

T Cells ◽

Protein Kinase C ◽

T Cell ◽

Protein Kinase ◽

Immunological Synapse ◽

Interleukin 2 ◽

Cell Receptor ◽

Kinase C ◽

Primary Mouse ◽

Nfat Activation

Protein kinase C (PKC)θ is an established component of the immunological synapse and has been implicated in the control of AP-1 and NF-κB. To study the physiological function of PKCθ, we used gene targeting to generate a PKCθ null allele in mice. Consistently, interleukin 2 production and T cell proliferative responses were strongly reduced in PKCθ-deficient T cells. Surprisingly, however, we demonstrate that after CD3/CD28 engagement, deficiency of PKCθ primarily abrogates NFAT transactivation. In contrast, NF-κB activation was only partially reduced. This NFAT transactivation defect appears to be secondary to reduced inositol 1,4,5-trisphosphate generation and intracellular Ca2+ mobilization. Our finding suggests that PKCθ plays a critical and nonredundant role in T cell receptor–induced NFAT activation.

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Protein kinase C modulates cytosolic free calcium by stimulating calcium pump activity in Jurkat T cells

Cell Calcium ◽

10.1016/0143-4160(95)90015-2 ◽

1995 ◽

Vol 18 (6) ◽

pp. 526-541 ◽

Cited By ~ 30

Author(s):

M. Balasubramanyam ◽

J.P. Gardner

Keyword(s):

T Cells ◽

Protein Kinase C ◽

Protein Kinase ◽

Calcium Pump ◽

Free Calcium ◽

Jurkat T Cells ◽

Cytosolic Free Calcium ◽

Kinase C ◽

Pump Activity

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Role of protein kinase C in T-cell antigen receptor regulation of p21ras: evidence that two p21ras regulatory pathways coexist in T cells

Molecular and Cellular Biology ◽

10.1128/mcb.12.7.3305-3312.1992 ◽

1992 ◽

Vol 12 (7) ◽

pp. 3305-3312

Author(s):

M Izquierdo ◽

J Downward ◽

J D Graves ◽

D A Cantrell

Keyword(s):

T Cells ◽

Protein Kinase C ◽

Protein Kinase ◽

Kinase Inhibitor ◽

Antigen Receptor ◽

Permeabilized Cell ◽

Regulatory Pathways ◽

Kinase C ◽

Stimulation Of

T-lymphocyte activation via the antigen receptor complex (TCR) results in accumulation of p21ras in the active GTP-bound state. Stimulation of protein kinase C (PKC) can also activate p21ras, and it has been proposed that the TCR effect on p21ras occurs as a consequence of TCR regulation of PKC. To test the role of PKC in TCR regulation of p21ras, a permeabilized cell system was used to examine TCR regulation of p21ras under conditions in which TCR activation of PKC was blocked, first by using a PKC pseudosubstrate peptide inhibitor and second by using ionic conditions that prevent phosphatidyl inositol hydrolysis and hence diacylglycerol production and PKC stimulation. The data show that TCR-induced p21ras activation is not mediated exclusively by PKC. Thus, in the absence of PKC stimulation, the TCR was still able to induce accumulation of p21ras-GTP complexes, and this stimulation correlated with an inactivation of p21ras GTPase-activating proteins. The protein tyrosine kinase inhibitor herbimycin could prevent the non-PKC-mediated, TCR-induced stimulation of p21ras. These data indicate that two mechanisms for p21ras regulation coexist in T cells: one PKC mediated and one not. The TCR can apparently couple to p21ras via a non-PKC-controlled route that may involve tyrosine kinases.

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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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