Analysis of regulatory mechanism for cell polarity formation by JNK binding molecules during migration

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JNK/SAPK-associated protein 1(JSAP1) mediated an association between focal adhesion kinase (FAK) and JNK, which was induced by either co-expression of Src or attachment of cells to fibronectin (FN). Complex formation of FAK with JSAP1 and p130 Crk-associated substrate (p130^<Cas>) resulted in augmentation of FAK activity and phosphorylation of both JSAP1 and p130^<Cas>, which required p130^<Cas> hyperphosphorylation and was abolished by inhibition of Src. JNK activation by FN was enhanced by JSAP1, which was suppressed by disrupting the FAK/p130^<Cas> pathway by expression of a dominant-negative form of p130^<Cas> or by inhibiting Src. JSAP1 was co-localized with JNK and phosphorylated FAK at the leading edge and stimulated of cell migration, which depended on its JNK binding domain and was suppressed by inhibition of JNK. The level of JSAP1 mRNA correlated with advanced malignancy in brain tumors, unlike other JIPs. We propose that the JSAP1/FAK complex functions cooperatively as a sc … More affold for the JNK signaling pathway and regulator of cell migration on FN, and we suggest that JSAP1 is also associated with malignancy in brain tumors.MT1-MMP expression promoted FN-induced cell migration, which was accompanied by FN degradation and reduction of stable focal adhesions, which function as anchors for actin-stress fibers, and attenuated integrin clustering. The attenuation of integrin clustering was abrogated by MT1-MMP inhibition. When cultured on fibronectin, HT1080 cells, which endogenously express MT1-MMP, showed so-called motile morphology with well-organized focal adhesion formation, well-oriented actin-stress fiber formation and the lysis of FN through trails of cell migration. Inhibition of endogenous MT1-MMP resulted in the suppression of FN lysis and cell migration and promotion of stable focal adhesion formation concomitant with enhanced phosphorylation of tyrosine 397 of FAK and reduced ERK activation. These results suggest that lysis of the extracellular matrix by MT1-MMP promotes focal adhesion turnover and subsequent ERK activation, which in turn stimulates cell migration. Less