Molecular basis for regulation of Src by the docking protein p130Cas.
The docking protein p130Cas (Cas) becomes tyrosine-phosphorylated in its central substrate domain in response to extracellular stimuli such as integrin-mediated cell adhesion, and transmits signals through interactions with various intracellular signaling molecules such as the adaptor protein Crk. Src-family kinases (SFKs) bind a specific site in the carboxyl-terminal region of Cas and subsequently SFKs phosphorylate progressively the substrate domain in Cas. In this study crystallography, mutagenesis and binding assays were used to understand the molecular basis for Cas interactions with SFKs. Tyrosine phosphorylation regulates binding of Cas to SFKs, and the primary site for this phosphorylation, Y762, has been proposed. A phosphorylated peptide corresponding to Cas residues 759MEDpYDYVHL767 containing the key phosphotyrosine was crystallized in complex with the SH3-SH2 domain of the SFK Lck. The results provide the first structural data for this protein-protein interaction. The motif in Cas 762pYDYV binds to the SH2 domain in a mode that mimics high-affinity ligands, involving dual contacts of Y762 and V765 with conserved residues in SFK SH2 domains. In addition, Y764 is in position to make an electrostatic contact after phosphorylation with a conserved SFK arginine that mediates interactions with other high-affinity SH2 binders. These new molecular data suggest that Cas may regulate activity of Src as a competing ligand to displace intramolecular interactions that occur in SFKs (between the C-terminal tail and the SH2 domain) and restrain and down-regulate the kinase in an inactive form.
Nasertorabi
Fariborz
F
Cancer Center, The Burnham Institute for Medical Research, La Jolla, California 92037, USA.
Tars
Kaspars
K
Becherer
Kathleen
K
Kodandapani
Ramadurgam
R
Liljas
Lars
L
Vuori
Kristiina
K
Ely
Kathryn R
KR
D000494:Allosteric Regulation; D050719:Crk-Associated Substrate Protein / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D016296:Mutagenesis; D010766:Phosphorylation; D011485:Protein Binding; D015398:Signal Transduction; D018909:src Homology Domains; D019061:src-Family Kinases / Q000737:chemistry* / Q000378:metabolism
D050719:Crk-Associated Substrate Protein; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D019061:src-Family Kinases