Suppresses SRC activation by recognizing and binding to active SRC and facilitating PTPN13-mediated dephosphorylation of SRC 'Tyr-419' leading to its inactivation. Inactivated SRC dissociates from this protein allowing the initiation of a new SRC inactivation cycle (By similarity). Involved in reorganization of the actin cytoskeleton. In nonmuscle cells, binds to ACTN1 (alpha-actinin-1), increases the affinity of ACTN1 to F-actin (filamentous actin), and promotes formation of actin stress fibers (PubMed:14729062, PubMed:22659164). Involved in regulation of the synaptic AMPA receptor transport in dendritic spines of hippocampal pyramidal neurons directing the receptors toward an insertion at the postsynaptic membrane. Links endosomal surface-internalized GRIA1-containing AMPA receptors to the alpha-actinin/actin cytoskeleton. Increases AMPA receptor-mediated excitatory postsynaptic currents in neurons (PubMed:15456832). Homodimer (By similarity). Interacts (via C-terminus only or via combined C-terminus and LIM domain, but not LIM domain only) with PTPN13 (via the second or fourth PDZ domains). Found in a complex with PTPN13 and TRIP6 (By similarity). Interacts (via PDZ domain) with ACTN1 and ACTN2 (via C-terminal SDL residues) (PubMed:14729062, PubMed:15456832). Interacts (via PDZ domain) with TRIP6 (via the second LIM domain or via the third LIM domain plus C-terminus) (By similarity). Interacts (via LIM domain) with GRIA1 (via C-terminus); this interaction as well as the interaction with alpha-actinin is required for their colocalization in early endosomes (PubMed:15456832). Interacts with PDLIM1 (PubMed:22659164). Forms (via LIM domain) a heterodimer with PDLIM3 (By similarity). Interacts directly with SRC (via kinase domain and to a lesser extent the SH2 domain) (By similarity). Localizes to actin stress fibers in nonmuscle cells (PubMed:14729062, PubMed:22659164). Colocalizes with GRIA1 in early endosomes. Enriched in numerous but not all spine-like structures along dendritic branches. Colocalizes with actin and enriched at sites containing larger amounts of actin and alpha-actinin. Targeted efficiently to spines via its PDZ domain-mediated interaction with the alpha-actinin/actin cytoskeletal complex. Localizes to synaptosomes in brain (PubMed:15456832). Colocalizes with F-actin. Colocalizes with TRIP6 at cell-cell contacts and lamellipodia. In the cytoplasm, displays a fibrillar pattern with characteristic thick fibers and occasional clusters. Colocalizes with the actin stress fibers. Oxidative stress induces redistribution from cytoskeleton to cytosol. Colocalizes with SRC at the perinuclear region, but not at focal adhesions (By similarity). Detected in several tissues, most prominent in brain and heart of adults (PubMed:7824279). Expressed in embryonic fibroblasts (PubMed:22659164). Phosphorylated on tyrosine residue(s). Can be dephosphorylated by PTPN13.