Protein kinase C activation inhibits tyrosine phosphorylation of Cbl and its recruitment of Src homology 2 domain-containing proteins.
One of the major proteins that is rapidly tyrosine phosphorylated upon stimulation of the TCR/CD3 complex is the 120-kDa product of the c-cbl protooncogene (Cbl). Upon activation, tyrosine-phosphorylated Cbl interacts with the Src homology 2 (SH2) domains of several signaling proteins, e.g., phosphatidylinositol 3-kinase (PI3-K) and CrkL. In the present study, we report that pretreatment of Jurkat T cells with PMA reduced the anti-CD3-induced tyrosine phosphorylation of Cbl and, consequently, its activation-dependent association with PI3-K and CrkL. A specific protein kinase C (PKC) inhibitor (GF-109203X) reversed the effect of PMA on tyrosine phosphorylation of Cbl and restored the activation-dependent association of Cbl with PI3-K and CrkL. We also provide evidence that PKCalpha and PKCtheta can physically associate with Cbl and are able to phosphorylate it in vitro and in vivo. Furthermore, a serine-rich motif at the C terminus of Cbl, which is critical for PMA-induced 14-3-3 binding, is also phosphorylated by PKCalpha and PKCtheta in vitro. These results suggest that, by regulating tyrosine and serine phosphorylation of Cbl, PKC is able to control the association of Cbl with signaling intermediates, such as SH2 domain-containing proteins and 14-3-3 proteins, which may consequently result in the modulation of its function.
Liu
Y
Y
Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA.
Liu
Y C
YC
Meller
N
N
Giampa
L
L
Elly
C
C
Doyle
M
M
Altman
A
A
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D004789:Enzyme Activation / Q000235:genetics; D006801:Humans; D019169:Jurkat Cells; D009687:Nuclear Proteins / Q000378:metabolism; D050722:Oncogene Protein v-cbl; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014443:Tyrosine / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018909:src Homology Domains / Q000187:drug effects / Q000235:genetics
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; C082869:CRKL protein; D009687:Nuclear Proteins; D050722:Oncogene Protein v-cbl; D011506:Proteins; D015682:Retroviridae Proteins, Oncogenic; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014443:Tyrosine; D012694:Serine; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate