Functional analysis of exon 2 of p130Cas in fibroblasts derived from exon 2-specific knockout mice.

p130Cas (Cas, Crk-associated substrate) is an adaptor molecule composed of an N-terminal Src homology 3 (SH3) domain, a substrate domain (SD), and a C-terminal Src binding domain (SBD). The SH3 domain of Cas has been shown to associate with various signaling molecules, including focal adhesion kinase (FAK), but its role in cellular function remains unclear. To address this issue, we established and analyzed primary fibroblasts derived from mice expressing a truncated Cas lacking the exon 2 encoding the SH3 domain (Cas exon 2/). In comparison to wild-type (Cas exon 2+/+) cells, Cas exon 2/ primary fibroblasts showed delayed migration in wound healing and reduced spreading on fibronectin (FN), which would be due to reduced complex formation of Cas exon 2/ with FAK and CrkII and also to impaired localization of Cas exon 2/ to focal adhesions on FN. In addition, to analyze downstream signaling pathway regulated by Cas exon 2, we compared gene expression profiles between Cas exon 2+/+ and Cas exon 2/ cells by a microarray analysis. Interestingly, we found that Cas exon 2-deficiency upregulated expression of CXC Chemokine Receptor-4 (CXCR4), CC Chemokine Receptor-5 (CCR5), and thrombospondin 4, which are implicated in cell motility and adhesion. These results define the role of Cas SH3-encoding exon in cell motility, FAK/Cas/CrkII complex formation, recruitment of Cas to focal adhesions, and regulation of cell adhesion-associated gene expression in primary fibroblasts.

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