Transcriptional coactivator for androgen receptor (AR) and serum response factor (SRF). Contributes to the regulation of cell adhesion, spreading and cell migration and acts as a negative regulator in integrin-mediated cell adhesion events. Suppresses the integrin-induced tyrosine phosphorylation of paxillin (PXN). May play a critical role as an adapter protein in the formation of the adhesion zone in osteoclasts. Negatively regulates B-cell antigen receptor (BCR) signaling. Interacts with unphosphorylated ITGA4. Interacts with AR and SRF (By similarity). Interacts with PTK2B/PYK2, PTPN22 and PTPN12. Interacts (via LD motif 3) with LYN and the interaction is induced upon B-cell antigen receptor (BCR) activation. Interacts (via LD motif 3) with PTK2/FAK. Shuttles between the cytoplasm and nucleus. Recruited to the cell membrane following B-cell antigen receptor (BCR) cross-linking in B-cells. Enhanced focal adhesion kinase activity (PTK2/FAK) attenuates its nuclear accumulation and limits its ability to enhance serum response factor (SRF)-dependent gene transcription. Targeting to focal adhesions is essential for its tyrosine phosphorylation in response to bombesin (By similarity). Expressed in osteoclasts (at protein level). Highly expressed in vascular smooth muscle. The LIM domain 3 is critical for focal adhesion targeting and the suppression of paxillin (PXN) tyrosine phosphorylation. The LIM domain 3 alone or both LIM domains 3 and 4 can mediate interaction with AR. Phosphorylated on tyrosine residues. Phosphorylation on Tyr-72 is important for its inhibitory function. Bombesin stimulates phosphorylation on Tyr-22, Tyr-62 and Tyr-72 (By similarity). Belongs to the paxillin family.