PSM/SH2B1 splice variants: critical role in src catalytic activation and the resulting STAT3s-mediated mitogenic response.
A role of PSM/SH2B1 had been shown in mitogenesis and extending to phenotypic cell transformation, however, the underlying molecular mechanism remained to be established. Here, four alternative PSM splice variants and individual functional protein domains were compared for their role in the regulation of Src activity. We found that elevated cellular levels of PSM variants resulted in phenotypic cell transformation and potentiated cell proliferation and survival in response to serum withdrawal. PSM variant activity presented a consistent signature pattern for any tested response of highest activity observed for gamma, followed by delta, alpha, and beta with decreasing activity. PSM-potentiated cell proliferation was sensitive to Src inhibitor herbimycin and PSM and Src were found in the same immune complex. PSM variants were substrates of the Src Tyr kinase and potentiated Src catalytic activity by increasing the V(max) and decreasing the K(m) for ATP with the signature pattern of variant activity. Dominant-negative PSM peptide mimetics including the SH2 or PH domains inhibited Src catalytic activity as well as Src-mediated phenotypic cell transformation. Activation of major Src substrate STAT3 was similarly potentiated by the PSM variants in a Src-dependent fashion or inhibited by PSM domain-specific peptide mimetics. Expression of a dominant-negative STAT3 mutant blocked PSM variant-mediated phenotypic cell transformation. Our results implicate an essential role of the PSM variants in the activation of the Src kinase and the resulting mitogenic response--extending to phenotypic cell transformation and involving the established Src substrate STAT3.
Zhang
Manchao
M
Department of Biochemistry, West Virginia University, School of Medicine, Morgantown, West Virginia 26506-9142, USA.
Deng
Youping
Y
Riedel
Heimo
H
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics*; D000818:Animals; D000954:Antigens, Surface / Q000235:genetics*; D002384:Catalysis; D002460:Cell Line; D029721:Drosophila Proteins; D004789:Enzyme Activation; D043425:Glutamate Carboxypeptidase II / Q000235:genetics*; D006801:Humans; D051379:Mice; D008934:Mitogens; D020033:Protein Isoforms / Q000502:physiology*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000502:physiology*; D019061:src-Family Kinases / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000954:Antigens, Surface; D029721:Drosophila Proteins; D008934:Mitogens; D020033:Protein Isoforms; C107249:SH2B2 protein, human; D050796:STAT3 Transcription Factor; D016392:Proto-Oncogene Proteins pp60(c-src); D019061:src-Family Kinases; C473848:FOLH1 protein, human; D043425:Glutamate Carboxypeptidase II