ITGA4 encodes integrin alpha chain 4. Integrins are heterodimeric integral membrane proteins composed of an alpha chain and a beta chain. Unlike other integrin alpha chains, alpha 4 neither contains an I-domain, nor undergoes disulfide-linked cleavage. Although alpha 4 is variably cleaved to yield two unlinked chains, this cleavage is unnecessary for integrin assembly and function. Alpha 4 combines with beta 1 (ITGB1) on T-cells to form the integrin very late (activation) antigen 4 (VLA-4) that can bind to the extracellular matrix molecules fibronectin or thrombospondin, and is also a ligand for the cell surface molecule vascular cell adhesion molecule 1 (VCAM-1). In addition, alpha 4 combines with beta 7 to form the lymphocyte homing receptor known as LPAM-1 (lymphocyte Peyer Patch adhesion molecule 1). Integrins are also known to participate in cell-surface mediated signalling.