The PDGF receptor phosphorylates Tyr 138 in the c-Src SH3 domain in vivo reducing peptide ligand binding.
Treatment of quiescent NIH3T3 cells with PDGF BB results in the transient activation and hyperphosphorylation of the protein-tyrosine kinase, c-Src. These effects correlate with novel serine and tyrosine phosphorylations in the N-terminal non-catalytic region of the molecule, which contains an SH3 and SH2 domain. In this study, a site of PDGF-induced tyrosine phosphorylation was mapped to Tyr 138 in the SH3 domain; Tyr 138 is exposed on the SH3 peptide binding surface. This same site is phosphorylated in vitro by the PDGF receptor when purified baculovirus-expressed c-Src is complexed with the activated receptor. Phosphorylation of Tyr 138 required association of c-Src with the PDGF receptor via its SH2 domain. When a c-Src Phe 138 mutant was stably expressed in Src- mouse fibroblasts, it was activated to the same extent as wild type c-Src following PDGF stimulation, indicating that phosphorylation of this site is not required for PDGF-mediated activation. However, Tyr 138 phosphorylation was found to diminish SH3 domain peptide ligand binding ability in vitro.
Broome
M A
MA
Molecular Biology and Virology Laboratory, The Salk Institute, La Jolla, California 92037, USA.
Hunter
T
T
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002478:Cells, Cultured; D051379:Mice; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification; D016415:Sequence Alignment; D018411:Spodoptera; D014443:Tyrosine / Q000378:metabolism*; D018909:src Homology Domains / Q000502:physiology; D019061:src-Family Kinases
D010982:Platelet-Derived Growth Factor; D011994:Recombinant Proteins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D017479:Receptors, Platelet-Derived Growth Factor; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases