Identification of SNT/FRS2 docking site on RET receptor tyrosine kinase and its role for signal transduction

SNT/FRS2 is a lipid anchored docking protein that contains an amino-termina l myristylation signal, followed by a phosphotyrosine-binding (PTB) domain and a carboxy-terminal region with multiple tyrosine residues. Here we show that the SNT/FRS2 PTB domain binds to RET receptor tyrosine kinase activat ed by glial cell line-derived neurotrophic factor (GDNF) or multiple endocr ine neoplasia (MEN) 2 mutations. Analyses by site directed-mutagenesis reve aled that it binds to tyrosine 1062 in RET that is also known to be a bindi ng site for the SHC adaptor protein. Whereas SHC bound to RET was associate d with GRB2 and GAB1 proteins, SNT/FRS2 was associated with GRB2 only, sugg esting that SNT/FRS2 is involved mainly in the activation of the RAS/mitoge n activated protein kinase (MAPK) pathway but not the phosphatidylinositol 3-kinase (PI3-K)/AKT pathway. In addition, phosphorylated SNT/FRS2 appeared to directly complex with SHP-2 tyrosine phosphatase. These results suggest that tyrosine 1062 in RET provides a site for the interaction of multiple signaling molecules and that the balance of SHC and SNT/FRS2 binding may af fect the nature of the intracellular signaling for cell proliferation, diff erentiation and survival induced by activated RET.