SKAP55 recruits to lipid rafts and positively mediates the MAPK pathway upon T cell receptor activation.
T cell receptor (TCR) engagement triggers a series of events including protein tyrosine kinase activation, tyrosine phosphorylation of adapter proteins, and multiple protein-protein interactions. We observed that adapter protein SKAP55, the Src kinase-associated phosphoprotein, formed homodimers through its SH3 domain and SK region. SKAP55 as a substrate interacted with Fyn kinase in vivo. In Jurkat cells, interaction between SKAP55 and Fyn kinase depended on TCR activation. Stable overexpression of SKAP55 in Jurkat cells caused mitogen-activated protein kinase activation following TCR engagement. Anti-CD3 stimulation also promoted the interaction of SKAP55 with Grb-2 in T cells. Mutational analysis revealed that tyrosine 271 in SKAP55 played a pivotal role for interaction with both Fyn kinase and adapter protein Grb-2, indicating that the Fyn-phosphorylated SKAP55 transiently associates with adapter Grb-2 to mediate mitogen-activated protein kinase activation. Intriguingly, T cell receptor engagement dramatically induced the translocation of endogenous SKAP55 to lipid rafts where SKAP55 was found to interact with Fyn kinase, suggesting that the positive function of SKAP55 via its association with Fyn and other signaling components may have been involved in raft-mediated T cell activation.
Wu
Liangtang
L
Mammalian Cell Genetics, Biotechnology Research Institute, National Research Council Canada, 6100 Royalmount Avenue, Montreal, Quebec H4P 2R2, Canada.
Yu
Zhenbao
Z
Shen
Shi-Hsiang
SH
D048868:Adaptor Proteins, Signal Transducing; D004789:Enzyme Activation; D051380:GRB2 Adaptor Protein; D006801:Humans; D019169:Jurkat Cells; D050356:Lipid Metabolism; D008213:Lymphocyte Activation; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011948:Receptors, Antigen, T-Cell; C108336:SKAP1 protein, human; C092947:SLP-76 signal Transducing adaptor proteins; D014443:Tyrosine; C494957:FYN protein, human; D051076:Proto-Oncogene Proteins c-fyn; D020928:Mitogen-Activated Protein Kinases