Stimulus-induced phosphorylation of PKCθ at the Ser-695 hydrophobic-motif in human T lymphocytes

Department of Biochemistry, Royal College of Surgeons in Ireland, Dublin, Leinster, Ireland
Biochemical and Biophysical Research Communications (Impact Factor: 2.3). 09/2005; 334(2):619-30. DOI: 10.1016/j.bbrc.2005.06.136
Source: PubMed


Protein kinase C (PKC) is a family of serine/threonine kinases whose activity is controlled, in part, by phosphorylation on three conserved residues that are located on the catalytic domain of the enzyme, known as the activation-loop, the turn-motif, and the C-terminal hydrophobic-motif sites. Using a panel of phospho-specific antibodies, we have determined that PKC beta(I) and delta are constitutively phosphorylated on all three sites in unstimulated and activated T cells. Although PKC theta is constitutively phosphorylated at the activation-loop and turn-motif sites in T cells, PMA or anti-CD3/CD28 stimulation results in an increase in phosphorylation at the hydrophobic-motif (Ser695), an event that coincides with translocation of the enzyme from the cytosol/cytoskeleton to the membrane. Studies on the stimulus-induced phosphorylation of PKC theta demonstrate that an upstream kinase activity involving a conventional PKC isoform(s) and the PI3-kinase pathway, rather than autophosphorylation or the rapamycin-sensitive mTOR pathway, regulates this site in T lymphocytes. However, hydrophobic-motif phosphorylation does not appear to control membrane translocation, suggesting that this site may control other aspects of PKC theta signalling.

Full-text preview

Available from:
  • Source
    • "PKCθ also regulates Rap1 and LFA-1 upon TCR ligation and controls antigen induced migration [23], [55]. Our data demonstrating that T538 and S676 are phosphorylated in response to CCR7 signaling are similar to that seen upon TCR activation [16], [17]. These results suggest that while CCR7 signaling via PKCθ to T cell motility may share some pathways in common with TCR signaling, the effects of PKCθ downstream of CCR7 may be separate from the pathways that have already been identified downstream of TCR signaling. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Cell motility is a fundamental process crucial for function in many cell types, including T cells. T cell motility is critical for T cell-mediated immune responses, including initiation, activation, and effector function. While many extracellular receptors and cytoskeletal regulators have been shown to control T cell migration, relatively few signaling mediators have been identified that can modulate T cell motility. In this study, we find a previously unknown role for PKCθ in regulating T cell migration to lymph nodes. PKCθ localizes to the migrating T cell uropod and regulates localization of the MTOC, CD43 and ERM proteins to the uropod. Furthermore, PKCθ-deficient T cells are less responsive to chemokine induced migration and are defective in migration to lymph nodes. Our results reveal a novel role for PKCθ in regulating T cell migration and demonstrate that PKCθ signals downstream of CCR7 to regulate protein localization and uropod formation.
    Full-text · Article · Nov 2013 · PLoS ONE
  • Source
    • "A physical interaction of PKCθ with the cytoplasmatic tail of CD28 has been shown to be essential in this recruitment mechanism (Kong et al., 2011). Subsequently, PKCθ is phosphorylated at different sites (Bauer et al., 2001; Bi et al., 2001; Liu et al., 2002; Freeley et al., 2005; Lee et al., 2005) and autophosphorylated at Thr-219 (Thuille et al., 2005). Recently, Chuang et al. (2011) identified the MAP4K3 GCK-like kinase (GLK) as a kinase that directly phosphorylates PKCθ at Thr-538 which is essential to activation of NF-κB in T cells. "
    [Show abstract] [Hide abstract]
    ABSTRACT: It is well established that members of the protein kinase C (PKC) family seem to have important roles in T cells. Focusing on the physiological and non-redundant PKC functions established in primary mouse T cells via germline gene-targeting approaches, our current knowledge defines two particularly critical PKC gene products, PKCθ and PKCα, as the "flavor of PKC" in T cells that appear to have a positive role in signaling pathways that are necessary for full antigen receptor-mediated T cell activation ex vivo and T cell-mediated immunity in vivo. Consistently, in spite of the current dogma that PKCθ inhibition might be sufficient to achieve complete immunosuppressive effects, more recent results have indicated that the pharmacological inhibition of PKCθ, and additionally, at least PKCα, appears to be needed to provide a successful approach for the prevention of allograft rejection and treatment of autoimmune diseases.
    Full-text · Article · Aug 2012 · Frontiers in Immunology
  • Source
    • "S676 is constitutively autophosphorylated in the turn motif of recombinant PKC-θ isolated from HEK293T cells and E. coli expression system (Liu et al., 2002; Czerwinski et al., 2005). Basal S676 phosphorylation of PKC-θ has also been observed in Jurkat T cells, CTL clone AB.1 cells, and primary CD4+ T cells (Freeley et al., 2005; Puente et al., 2005; Lee et al., 2010). The basal level of PKC-θ S676 phosphorylation is moderately increased in mouse primary CD4+ T cells upon anti-CD3/CD28 costimulation (Lee et al., 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Protein kinase C (PKC)-θ is a serine/threonine kinase belonging to the calcium-independent novel PKC subfamily; its expression is restricted to certain tissues and cell types, including T cells. The signals delivered from T cell receptor (TCR) and CD28 costimulatory molecules trigger PKC-θ catalytic activation and membrane translocation to the immunological synapse, leading to activation of NF-κB, AP-1, and NF-AT. These transcription factors are important for T cell survival, activation, and differentiation. Phosphorylation of PKC-θ at multiple Ser/Thr/Tyr residues is induced in T cells during TCR signaling. Some phosphorylation sites play critical roles in the regulation of PKC-θ function and downstream signaling. The regulation mechanisms for PKC-θ phosphorylation sites are now being revealed. In this review, we discuss the current understanding of the regulation of PKC-θ function by phosphorylation during TCR signaling.
    Full-text · Article · Jul 2012 · Frontiers in Immunology
Show more