Protein Kinase Cθ Is a Specific Target for Inhibition of the HIV Type 1 Replication in CD4+ T Lymphocytes

Abstract

The novel protein serine/threonine kinase C (PKC) isoform is selectively expressed in T lymphocytes but not B lymphocytes, erythrocytes, polymorphonuclear neutrophils, monocytes, or macrophages (1). Other PKC isotypes (␣, ␤, ␦, ⑀, , and ) are also expressed in T cells, but PKC is essential for T cell receptor/CD3-mediated activation events (2, 3). Among novel PKCs, PKC displays the highest amino acid similarity with PKC␦, not only in the catalytic or kinase core and the diacylglycerol binding regulatory domain C1 but mainly in the NH 2 -terminal V1 domain (2). However, V3 domain of PKC is unique and does not show significant similarity with any other PKC isoforms, including PKC␦. As a result, PKC provides a molecular basis for isotype selectivity and the non-redundant activity of distinct PKC isoenzymes in T cells (4).PKC kinase activity is regulated by phosphorylation of the activation-loop residue Thr 538 on the catalytic domain during T cell activation (5). Residue Thr 538 has been described as critical for PKC catalytic activity for regulating phosphorylation of the hydrophobic motif and for enabling CD3-mediated nuclear factor-B (NF-B) activation (6). PKC also shows the unique property of being translocated to the plasma membrane lipid rafts during the immunological synapse between T cells and antigen-presenting cells (7-9). Recruitment of PKC to the immunological synapse induces the activation of intracellular signaling pathways as the mitogen-activated protein kinase and the NF-B pathway (10), essential for the regulation of T cell growth-promoting genes as IL-2 (interleukin-2) (3, 11). NF-B is also critical for the replication of the human immunodeficiency virus type 1 (HIV-1) in human blood CD4 ϩ T cells (12). The main NF-B inhibitor, IB␣, binds to the NF-B nuclear localization signal to keep it inactive in the cytoplasm in the absence of activation. Upon T cell activation, IB␣ is phosphorylated by the IB kinase complex and degraded in the proteasome (13), releasing the nuclear localization signal and allowing NF-B translocation to the nucleus, where binds to cognate sequences in inducible gene promoters (14), as the HIV-1 long terminal promoter (LTR).The main target for HIV-1 infection is the CD4 ϩ T cell population, in particular memory CD4 ϩ T cells that are generated by antigen recognition (15). The viral genome can be permanently integrated in the chromosomes of these cells, producing latent reservoirs with long half-life. HIV-1-infected memory T cells remain undetectable by the immune system and the highly active antiretroviral therapy (HAART) 4 when they are in a resting state, but they are able to release new batches of virions after

Protein kinase C-δ signaling regulates glucagon secretion from pancreatic islets

“…Moreover, the results obtained with rottlerin were compatible with those obtained utilizing more selective approaches to inhibit PKCδ in a previous report (17). It was recently reported rottlerin also inhibited PKCθ (23). However, our data indicates that PKCθ is not involved PMA-induced glucagon secretion.…”

“…2). It was recently reported that rottlerin also inhibited PKCθ another nPKC isoform, with IC50 of 1.6 μM and less than 3 μM of rottlerin selectively inhibited PKCθ (23). PMA-induced glucagon secretion was not suppressed by less than 2.5 μM of rottlerin, suggesting that PKCθ was not involved in PMA-induced glucagon secretion (Fig.…”

The Endocytosis and Signaling of the γδ T Cell Coreceptor WC1 Are Regulated by a Dileucine Motif

“…In contrast, the PKC u inhibitor Rottlerin did not inhibit wild-type CD4/WC1 endocytosis, even at the high dose of 10 mM, which inhibits PKC u, d, and z (Fig. 4A) (36). These results suggest that phosphorylation by PKC a or b, but not by PKC u, d, or z, is necessary for optimal WC1 endocytosis in Jurkat T cells; additionally, although phosphorylation of S13 or S14 is not required for PMA-induced endocytosis in Jurkat T cells (Fig.…”

“…Because the serine mutant CD4/WC1S13A/S14A reduced PMAinduced endocytosis when it was expressed in 293T cells but not in Jurkat T cells, we investigated whether WC1 endocytosis in Jurkat T cells was independent of serine/threonine phosphorylation by PKC using the inhibitors Gö6983 and Rottlerin (36). The PKC a, b, d, or z inhibitor Gö6983 significantly reduced the PMAinduced endocytosis of wild-type CD4/WC1 (Fig.…”

Reactivation of latently infected HIV-1 viral reservoirs and correction of aberrant alternative splicing in the LMNA gene via AMPK activation: Common mechanism of action linking HIV-1 latency and Hutchinson–Gilford progeria syndrome

“…Strikingly, inhibition of PKCh through the use of rottlerin prevented PKCh translocation to lipid rafts, repressed NF-kB, and reduced HIV-1 replication more than 20-fold in MT-2 and Jurkat cells and more than 4-fold in peripheral blood lymphocytes [131]. Interestingly, PKCh has recently been shown to mediate T cell gene expression (i.e.…”