Cytoskeletal protein involved in actin-membrane attachment at sites of cell adhesion to the extracellular matrix (focal adhesion). Interacts in vitro with VCL/vinculin as well as to the SH3 domain of SRC and, when tyrosine phosphorylated, to the SH2 domain of CRK (PubMed:7534286). Interacts with GIT1 (PubMed:10938112). Interacts with NUDT16L1/SDOS (By similarity). Interacts with PTK2/FAK1 (PubMed:14527389). Interacts with PTK2B/PYK2 (PubMed:19358827). Interacts with ASAP2 (PubMed:10749932). Interacts with unphosphorylated ITGA4 (PubMed:10604475). Interacts with RNF5 (PubMed:12861019). Interacts with PDCD10 (PubMed:20489202). Interacts with NEK3, the interaction is prolactin-dependent (PubMed:17297458). Interacts with PTK6 (PubMed:15572663). Interacts with TGFB1I1 (By similarity). Interacts with SORBS1 (PubMed:17462669). Interacts with PARVB (PubMed:22869380). Interacts (via LD motif 4) with PARVA/PARVIN (PubMed:15817463, PubMed:18508764, PubMed:18940607). Interacts (via LD motif 4) with ILK (PubMed:15817463, PubMed:18508764, PubMed:18940607). Interacts (via cytoplasmic domain) with CEACAM1; the interaction is phosphotyrosyl-dependent (PubMed:11035932). Interacts with LIMA1; this complex stabilizes actin dynamics (PubMed:24694988). Interacts with CD36 (via C-terminus) (PubMed:20037584). Interacts strongly with PTK2/FAK1 and weakly with VCL/vinculin. Interacts strongly with VCL/vinculin but only weakly with PTK2/FAK1. Colocalizes with integrins at the cell periphery. Colocalize with PXN to membrane ruffles and the leading edge of migrating cells (PubMed:23128389). Phosphorylated by MAPK1/ERK2 (By similarity). Phosphorylated on tyrosine residues during integrin-mediated cell adhesion, embryonic development, fibroblast transformation and following stimulation of cells by mitogens. Phosphorylation at Ser-244 by CDK5 reduces its interaction with PTK2/FAK1 in matrix-cell focal adhesions (MCFA) during oligodendrocytes (OLs) differentiation. Phosphorylation at Tyr-31 and Tyr-118 by PTK6 promote the activation of RAC1 via CRK/CrKII, thereby promoting migration and invasion. Phosphorylation at Ser-250 by SLK is required for PXN redistribution and cell motility (PubMed:23128389). Belongs to the paxillin family.