Protein p130Cas constitutes an adaptor protein mainly involved in integrin signaling downstream of Src kinase. Owing to its modular structure, p130Cas acts as a general regulator of cancer cell growth and invasiveness induced by different oncogenes. However, other mechanisms of p130Cas signaling leading to malignant progression are poorly understood. Here, we show a novel interaction of p130Cas with Ser/Thr kinase PKN3, which is implicated in prostate and breast cancer growth downstream of phosphoinositide 3-kinase. This direct interaction is mediated by the p130Cas SH3 domain and the centrally located PKN3 polyproline sequence. PKN3 is the first identified Ser/Thr kinase to bind and phosphorylate p130Cas and to colocalize with p130Cas in cell structures that have a pro-invasive function. Moreover, the PKN3-p130Cas interaction is important for mouse embryonic fibroblast growth and invasiveness independent of Src transformation, indicating a mechanism distinct from that previously characterized for p130Cas. Together, our results suggest that the PKN3-p130Cas complex represents an attractive therapeutic target in late-stage malignancies.

• Keywords
• CAS, BCAR1, PKN3, SH3, Src, p130Cas,
• MeSH
• Fibroblasts metabolism   MeSH
• Phosphorylation MeSH
• Phosphothreonine metabolism   MeSH
• Neoplasm Invasiveness MeSH
• Stress Fibers metabolism   MeSH
• Humans MeSH
• Mice, Nude MeSH
• Neoplasms metabolism   pathology   MeSH
• Podosomes metabolism   MeSH
• Cell Movement MeSH
• Cell Proliferation MeSH
• Protein Kinase C metabolism   MeSH
• Pseudopodia metabolism   MeSH
• src-Family Kinases metabolism   MeSH
• Crk-Associated Substrate Protein metabolism   MeSH
• Protein Binding MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Phosphothreonine MeSH
• protein kinase N MeSH Browser
• Protein Kinase C MeSH
• src-Family Kinases MeSH
• Crk-Associated Substrate Protein MeSH

CAS is a docking protein downstream of the proto-oncogene Src with a role in invasion and metastasis of cancer cells. The CAS SH3 domain is indispensable for CAS-mediated signaling, but structural aspects of CAS SH3 ligand binding and regulation are not well understood. Here, we identified the consensus CAS SH3 binding motif and structurally characterized the CAS SH3 domain in complex with ligand. We revealed the requirement for an uncommon centrally localized lysine residue at position +2 of CAS SH3 ligands and two rather dissimilar optional anchoring residues, leucine and arginine, at position +5. We further expanded the knowledge of CAS SH3 ligand binding regulation by manipulating tyrosine 12 phosphorylation and confirmed the negative role of this phosphorylation on CAS SH3 ligand binding. Finally, by exploiting the newly identified binding requirements of the CAS SH3 domain, we predicted and experimentally verified two novel CAS SH3 binding partners, DOK7 and GLIS2.

• MeSH
• Amino Acids metabolism   MeSH
• Phosphorylation physiology   MeSH
• Humans MeSH
• Ligands MeSH
• Proto-Oncogene Mas MeSH
• Amino Acid Sequence MeSH
• Signal Transduction physiology   MeSH
• src Homology Domains physiology   MeSH
• Crk-Associated Substrate Protein metabolism   MeSH
• Protein Binding physiology   MeSH
• Binding Sites physiology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Amino Acids MeSH
• Ligands MeSH
• MAS1 protein, human MeSH Browser
• Proto-Oncogene Mas MeSH
• Crk-Associated Substrate Protein MeSH