Platelet-derived growth factor (PDGF) stimulates the association of SH2-Bbeta with PDGF receptor and phosphorylation of SH2-Bbeta.
We recently identified SH2-Bbeta as a JAK2-binding protein and substrate involved in the signaling of receptors for growth hormone and interferon-gamma. In this work, we report that SH2-Bbeta also functions as a signaling molecule for platelet-derived growth factor (PDGF). SH2-Bbeta fused to glutathione S-transferase (GST) bound PDGF receptor (PDGFR) from PDGF-treated but not control cells. GST fusion protein containing only the SH2 domain of SH2-Bbeta also bound PDGFR from PDGF-treated cells. An Arg to Glu mutation within the FLVRQS motif in the SH2 domain of SH2-Bbeta inhibited GST-SH2-Bbeta binding to tyrosyl-phosphorylated PDGFR. The N-terminal truncated SH2-Bbeta containing the entire SH2 domain interacted directly with tyrosyl-phosphorylated PDGFR from PDGF-treated cells but not unphosphorylated PDGFR from control cells in a Far Western assay. These results suggest that the SH2 domain of SH2-Bbeta is necessary and sufficient to mediate the interaction between SH2-Bbeta and PDGFR. PDGF stimulated coimmunoprecipitation of endogenous SH2-Bbeta with endogenous PDGFR in both 3T3-F442A and NIH3T3 cells. PDGF stimulated the rapid and transient phosphorylation of SH2-Bbeta on tyrosines and most likely on serines and/or threonines. Similarly, epidermal growth factor stimulated the phosphorylation of SH2-Bbeta; however, phosphorylation appears to be predominantly on serines and/or threonines. In response to PDGF, SH2-Bbeta associated with multiple tyrosyl-phosphorylated proteins, at least one of which (designated p84) does not bind to PDGFR. Taken together, these data strongly argue that, in response to PDGF, SH2-Bbeta directly interacts with PDGFR and is phosphorylated on tyrosine and most likely on serines and/or threonines, and acts as a signaling protein for PDGFR.
Rui
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Department of Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0622, USA.
Carter-Su
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D016475:3T3 Cells; D000818:Animals; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D051379:Mice; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D017479:Receptors, Platelet-Derived Growth Factor / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains
D010982:Platelet-Derived Growth Factor; D014443:Tyrosine; D004815:Epidermal Growth Factor; D017479:Receptors, Platelet-Derived Growth Factor