ASAP1 is an Arf GTPase activating protein (GAP) with activity towards Arf1 and Arf5 but not Arf6 However, it has been shown to bind GTP-Arf6 stably without GAP activity []. It has been implicated in cell growth, migration, and survival, as well as in tumor invasion and malignancy. It binds paxillin and cortactin, two components of invadopodia which are essential for tumor invasiveness. It also binds focal adhesion kinase (FAK) and the SH2/SH3 adaptor CrkL [, ]. ASAP1 contains an N-terminal BAR domain, followed by a Pleckstrin homology (PH) domain, an Arf GAP domain, ankyrin (ANK) repeats, and a C-terminal SH3 domain [].This entry represents the BAR domain of ASAP1. BAR domains form dimers that bind to membranes, induce membrane bending and curvature, and may also be involved in protein-protein interactions. The BAR domain of ASAP1 mediates membrane bending, is essential for function, and autoinhibits GAP activity by interacting with the PH and/or Arf GAP domains [].
This entry represents the N-terminal SH3 domain found in the CRK family members []. CRK adaptor proteins consists of SH2 and SH3 domains, which bind tyrosine-phosphorylated peptides and proline-rich motifs, respectively. They function downstream of protein tyrosine kinases in many signaling pathways started by various extracellular signals, including growth and differentiation factors. Cellular CRK (c-CRK) contains a single SH2 domain, followed by N-terminal and C-terminal SH3 domains. It is involved in the regulation of many cellular processes including cell growth, motility, adhesion, and apoptosis. CRK has been implicated in the malignancy of various human cancers [, ]. The N-terminal SH3 domain of CRK binds a number of target proteins including DOCK180, C3G, SOS, and cABL []. The CRK family includes two alternatively spliced protein forms, CRKI and CRKII, that are expressed by the CRK gene, and the CRK-like (CRKL) protein, which is expressed by a distinct gene (CRKL). CrkI lacks the regulatory phosphorylation site and C-terminal SH3 domain present in CrkII and CrkL [, ]. The N-terminal SH3 domain of CRKII has been shown to bind the recognizes proline-rich motifs (PRMs) found in cABL kinase; this interaction is involved in the regulation of cell spreading, microbial pathogenesis, and cancer metastasis [].
