Acts as an adapter protein downstream of several growth factor receptors to promote cell proliferation, migration, and redistribution of actin fibers (PubMed:24216110). Specifically involved in INS/insulin signaling pathway by mediating MAPK1/ERK2-MAPK3/ERK1 activation and DNA synthesis (PubMed:24216110). Promotes insulin-mediated membrane ruffling (By similarity). In response to vasoconstrictor peptide EDN1, involved in the activation of RAP1 downstream of PTK2B via interaction with phosphorylated BCAR1 (PubMed:19086031). Inhibits cell migration and invasion via regulation of TGFB-mediated matrix digestion, actin filament rearrangement, and inhibition of invadopodia activity (By similarity). May inhibit TGFB-SMAD signaling, via facilitating BCAR1 and SMAD2 and/or SMAD3 interaction (By similarity). Regulates EGF-induced DNA synthesis (PubMed:18722344). Required for the maintenance of ocular lens morphology and structural integrity, potentially via regulation of focal adhesion complex signaling (By similarity). Acts upstream of PTPRA to regulate the localization of BCAR1 and PTPRA to focal adhesions, via regulation of SRC-mediated phosphorylation of PTPRA (By similarity). Positively regulates integrin-induced tyrosine phosphorylation of BCAR1 (By similarity). Acts as a guanine nucleotide exchange factor (GEF) for small GTPases RALA, RAP1A and RRAS (By similarity). However, in a contrasting study, lacks GEF activity towards RAP1 (PubMed:22081014). Part of a complex comprised of PTPRA, BCAR1, BCAR3 (via SH2 domain) and SRC; the formation of the complex is dependent on integrin mediated-tyrosine phosphorylation of PTPRA (PubMed:22801373). Within the complex, interacts (via SH2 domain) with PTPRA (when phosphorylated on 'Tyr-798') (PubMed:22801373). Interacts (via Ras-GEF domain) with BCAR1 (PubMed:18722344, PubMed:19086031, PubMed:22081014). Interacts (via Ras-GEF domain) with NEDD9 (By similarity). Interacts with PTK2/FAK1 (By similarity). Interacts with PTPN1. Interacts (via SH2 domain) with EGFR (when tyrosine-phosphorylated) (PubMed:18722344). Localization to focal adhesions depends on interaction with PTPRA. Ubiquitously expressed. Found in several cancer cell lines, but not in nonmalignant breast tissue. The SH2 domain mediates interaction with tyrosine-phosphorylated proteins (PubMed:18722344). However, not involved in the binding to phosphorylated BCAR1 (PubMed:18722344). Required for cell cycle progression in response to INS/insulin (PubMed:24216110). Required for regulation of EFR-induced DNA synthesis (PubMed:18722344). The Ras-GEF domain appears to adopt a closed conformation rendering it incapable of carrying out canonical exchange factor function, this closed conformation is probably required for interaction with BCAR1. Phosphorylated on tyrosine residues. Overexpression confers anti-estrogen resistance via RRAS-independent activation of the PI3K pathway, and activation of the cyclin D1 promoter in breast cancer cell lines (PubMed:9582273). Plays a role in insulin-mediated ERK activation and DNA synthesis in breast cancer cells (PubMed:24216110). The guanine nucleotide exchange factor (GEF) activity is controversial. One study showed GEF activity towards RALA, RAP1A and RRAS (By similarity). However, in another study, a construct containing only the Ras-GEF domain lacks GEF activity towards RAP1 (PubMed:22081014).