Characterisation of the SH2 domain of the melanoma associated adaptor protein, ShcD/RaLP

ShcD/RaLP is the least characterised member of the Shc adaptor family of proteins. Shc adaptor proteins share the modular structural domains known as phosphotyrosine binding (PTB), Src homology 2 (SH2), and one or two collagen homology (CH1/CH2) domains. These domains are involved in binding activated receptor tyrosine kinases and co-ordinating the activation of various signalling pathways. ShcD is highly expressed in melanomas where high expression levels correlate with increasing vertical growth phase and invasive properties. Since ShcD is a signalling adaptor, its role in migration and invasion is likely to depend on the proteins with which it forms complexes. Previous studies in this lab have shown that the signalling scaffolding protein Gab1 interacts with the SH2 domain of ShcD. Interestingly a possible phosphorylation site has been identified by mass spectrometry within the SH2 domain of ShcD which could regulate binding to Gab1. I have made a S551D phosphomimic mutation in the SH2 domain of ShcD and shown that this inhibits interaction with Gab1 and other tyrosine phosphorylated proteins by GST pull-downs. This suggests that phosphorylation of the SH2 domain by a Ser/Thr kinases may negatively regulate ShcD-Gab1 induced signalling. Future studies will examine the effect of the mutation on ShcD mediated migration and identifying the biological function of kinases that phosphorylate the SH2 domain of ShcD.