| CIN85 was independently identified as Cbl-interacting protein of 85 kDa (1), Ruk (regulator of ubiquitous kinase) (2), SETA (SH3 domain-containing gene expressed in tumorigenic astrocytes) (3), and SH3KBP1 (SH3 domain kinase binding protein 1) (4). The genes encoding these proteins were isolated from either human (CIN85), rat (Ruk and SETA), or mouse (SH3KBP1) sources and share between 92% and 97% sequence identity, suggesting that they represent homologues of one gene. Differential promoter usage and alternative splicing is thought to occur in a tissue specific and developmentally regulated manner to generate a complex expression pattern of various transcripts and encoded protein isoforms (5). The main isoform in humans, CIN85, contains three N-terminal SH3 domains, a proline-rich region harboring several P-X-X-P motifs that provide recognition sites for SH3 domain-containing proteins, a PEST sequence implicated in CIN85 degradation, and a C-terminal coiled-coil region for oligomerization (1,2,5,6). The other molecular variants of CIN85 are shorter, N-terminally truncated proteins lacking one, two, or all three of the SH3 domains (1,5,6-8). Proteomic screens suggest that CIN85 is phosphorylated at multiple sites and the role of phosphorylation of some of these sites in regulation of intra- and intermolecular interactions of CIN85 cannot be excluded. CIN85 belongs to the CD2AP/CMS family of adaptor proteins and has been shown to interact with signaling molecules such as c-Cbl, Cbl-b, BLNK, p85/PI3K, GRB2, p130 Cas, and endophilins to coordinate the activity of multiple signaling cascades. Indeed, a growing body of evidence suggests that CIN85 is required for the regulation of a variety of cellular processes including vesicle-mediated transport (9-12), signal transduction (13,14), and cytoskeleton remodelling (15). |
