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 (By similarity). 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 (By similarity). 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). 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 (By similarity). 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.