Integrins alpha-4/beta-1 (VLA-4) and alpha-4/beta-7 are receptors for fibronectin. They recognize one or more domains within the alternatively spliced CS-1 and CS-5 regions of fibronectin. They are also receptors for VCAM1. Integrin alpha-4/beta-1 recognizes the sequence Q-I-D-S in VCAM1. Integrin alpha-4/beta-7 is also a receptor for MADCAM1. It recognizes the sequence L-D-T in MADCAM1. On activated endothelial cells integrin VLA-4 triggers homotypic aggregation for most VLA-4-positive leukocyte cell lines. It may also participate in cytolytic T-cell interactions with target cells. ITGA4:ITGB1 binds to fractalkine (CX3CL1) and may act as its coreceptor in CX3CR1-dependent fractalkine signaling (PubMed:23125415). ITGA4:ITGB1 binds to PLA2G2A via a site (site 2) which is distinct from the classical ligand-binding site (site 1) and this induces integrin conformational changes and enhanced ligand binding to site 1 (PubMed:18635536, PubMed:25398877). Heterodimer of an alpha and a beta subunit. The alpha subunit can sometimes be cleaved into two non-covalently associated fragments. Alpha-4 associates with either beta-1 or beta-7. Alpha-4 interacts with PXN, LPXN, and TGFB1I1/HIC5. Interacts with CSPG4 through CSPG4 chondroitin sulfate glycosaminoglycan. Interacts with JAML; integrin alpha-4/beta-1 may regulate leukocyte to endothelial cells adhesion by controlling JAML homodimerization. ITGA4:ITGB1 is found in a ternary complex with CX3CR1 and CX3CL1 (PubMed:23125415). Interacts with MDK (PubMed:15466886). ITGA4:ITGB1 interacts with MDK; this interaction mediates MDK-induced osteoblast cells migration through PXN phosphorylation (PubMed:15466886). The SG1 motif is involved in binding to chondroitin sulfate glycosaminoglycan and cell adhesion. Phosphorylation on Ser-1027 inhibits PXN binding. Belongs to the integrin alpha chain family.