Structural Studies On Integrin-Mediated C-Src Activation

c-Src gene was discovered to be the first proto oncogen. c Srcprotein is involved in multiple important signaling pathways, such as cellproliferation, cell differentiation, cell apotosis, cell adhesion and cellmigragtion. The malfunction of c Src or abnormal activation of itsactivity often will lead to various severe diseases including osteopetrosis,thrombus and different cancers. So c Src became a vital drug target and alot of c Src inhibitors were applied to preclinical and clinical studies.Integrin β3is involed in the activation of c Src. Three amino of“RGT”, located in terminal of the cytoplasmic domain of β3, can directlyinteract with SH3domain, and lead the activation of c Src and thedownstream cell signaling transduction. Protein’s function bases on itsstructure. The interaction between β3and c Src can’t separate from theirstructures. It is an unsolved question how integrin mediates the activationof c Src through the interaction of RGT and SH3due to the lack of thestructural information of the interaction between β3and c Src, althoughtheir single structure has been reported.This paper started with the crystal structure of RGT:SH3complexand successfully analyzed the crystal structure of complex by means of X ray diffraction crystallography. The structure shows the bindingmode and sites of RGT:SH3complex. This interaction is in anon classical way among the interactions of peptides with SH3. Thebinding site lies in the “N” Src loop of SH3, just in the opening of“zipper” formed by interactions among SH3and linker and catalyticdomain. We hypothesized that the combination of RGT and SH3breaksthe original force balance of them and primes the activation of c Src. Wevalidated the crystal structure model from protein interaction experimentsand activity assays in vitro and cell spreading assays in vivo accordingthe information provided by crystal structure. These results are consistentwith the crystal structure. Finally, based on structure information andfunction assays and previous research, we proposed the model ofintegrin mediated c Src activation. Our work will shed light on thedevelopment of new c Src protein inhibitor on the basis of block of theinteraction of integrin with c Src in pharmacy.