IDENTIFICATION OF SHC DOCKING SITE ON RET TYROSINE KINASE

The RET proto-oncogene encodes two isoforms of a receptor type tyrosin e kinase which plays a role in neural crest and kidney development, Di stinct germ-line mutations of RET have been associated inherited cance r syndromes MEN2A, MEN2B FMTC as well as with the congenital disorder Hirschsprung disease (HSCR), whereas somatic rearrangements (RET/PTCs) have been frequently detected in the papillary thyroid carcinoma, Des pite these findings, suggesting a relevant role for RET product in dev elopment and neoplastic processes, little is known about the signallin g triggered by this receptor, In this study, we have demonstrated that the transducing adaptor molecule She is recruited and activated by bo th Ret isoforms and by the rearranged cytoplasmatic Ret/ptc2 oncoprote ins as well as by the membrane bound receptor activated by MEN2A or by MEN2B associated mutations, Moreover, our analysis has identified the Ret tyrosine residue and the She domains involved in the interaction, In fact, here we show that both the phosphotyrosine binding domains o f She, PTB and SH2, interact with Ret/ptc2 in vitro, However, PTB doma in binds 20 folds higher amount of Ret/ptc2 than SH2, The putative bin ding site for either SH2 and PTB domains has been identified as Tyr586 of Ret/ptc2 (Tyr1062 on proto-Ret). In keeping with this finding, by using RET/PTC2-Y586F mutant, we have demonstrated that this tyrosine r esidue, the last amino acid but one before the divergence of the two R et isoforms, is the docking site for She.