Activation of the integrin effector kinase focal adhesion kinase in cancer cells is regulated by crosstalk between protein kinase Calpha and the PDZ adapter protein mda-9/Syntenin.
Aberrant adhesion signaling pathways in cancer cells underlie their deadly invasive capabilities. The adhesion-related PDZ adapter protein mda-9/syntenin is a positive regulator of cancer cell progression in breast cancer, melanoma, and other human cancers. In this study, we report that mda-9/syntenin mediates adhesion-mediated activation of protein kinase Calpha (PKCalpha) and focal adhesion kinase (FAK) by fibronectin (FN) in human breast cancer and melanoma cells. FN rapidly stimulated the expression of mda-9/syntenin and the activation of PKCalpha prior to activation of FAK. Inhibiting PKCalpha suppressed basal or FN-induced expression of mda-9/syntenin, as well as cell migration and invasion toward FN stimulated by mda-9/syntenin. Several lines of evidence suggested that activation of PKCalpha and expression of mda-9/syntenin were interdependent. First, mda-9/syntenin inhibition suppressed basal or FN-induced phosphorylation of PKCalpha at Thr(638/641), whereas PKCalpha inhibition suppressed basal or FN-induced expression of mda-9/syntenin. Second, inhibiting either mda-9/syntenin or PKCalpha suppressed FN-induced formation of integrin-beta(1)/FAK/c-Src signaling complexes. Third, inhibiting either mda-9/syntenin or PKCalpha suppressed FN-induced phosphorylation of FAK Tyr(397) and c-Src Tyr(416) and the induction of downstream effector signals to p38 and mitogen-activated protein kinase, Cdc42, and NF-kappaB. In summary, our findings offer evidence that mda-9/syntenin acts as a molecular adaptor linking PKCalpha and FAK activation in a pathway of FN adhesion by human breast cancer and melanoma cells.
Authors' Affiliations: Department of Biochemistry, College of Natural Sciences, Kangwon National University, Chuncheon 200-701, Republic of Korea.
Cheol
C
Hwangbo
Jaekyung
J
Kim
Jung Joon
JJ
Lee
Jeong-Hyung
JH
Lee
D000081247:CSK Tyrosine-Protein Kinase; D002448:Cell Adhesion / Q000187:drug effects / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D005353:Fibronectins / Q000235:genetics / Q000502:physiology; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D009369:Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D054731:PDZ Domains / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D051571:Protein Kinase C-alpha / Q000378:metabolism* / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020239:Receptor Cross-Talk / Q000502:physiology; D053676:Syntenins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D019061:src-Family Kinases
D005353:Fibronectins; D019012:Integrin beta1; D034741:RNA, Small Interfering; C109621:SDCBP protein, human; D053676:Syntenins; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019061:src-Family Kinases; C000631346:CSK protein, human; D051571:Protein Kinase C-alpha