Integrin alpha-4-containing integrins (ITGA4)

Integrin alpha-4-containing integrins are a subset of the integrin family characterized by the presence of the alpha-4 subunit (ITGA4, also known as CD49d). This subunit can non-covalently pair with either the beta-1 subunit to form alpha-4-beta-1 (VLA-4) or the beta-7 subunit to form alpha-4-beta-7 (LPAM-1) [4, 6, 7]. These heterodimeric receptors are primarily expressed on the surface of various leukocytes, including lymphocytes, monocytes, and eosinophils, where they mediate critical cell-cell and cell-extracellular matrix interactions [1, 4, 15]. Their primary biological function involves the regulation of leukocyte trafficking and homing to sites of inflammation by binding to ligands such as Vascular Cell Adhesion Molecule-1 (VCAM-1) and Mucosal Addressin Cell Adhesion Molecule-1 (MAdCAM-1) [1, 7, 12]. In pathological contexts, alpha-4 integrins play a central role in the development of autoimmune and inflammatory diseases, such as multiple sclerosis and inflammatory bowel disease, by facilitating the infiltration of inflammatory cells into the central nervous system and gastrointestinal tract, respectively [1, 4, 17]. They are also implicated in cancer progression, contributing to tumor cell migration, metastasis, and drug resistance in conditions like leukemia [4, 5, 12]. Consequently, these integrins have become significant therapeutic targets. Drugs like natalizumab, which blocks the alpha-4 subunit, and vedolizumab, which selectively targets the alpha-4-beta-7 complex, are used to treat these conditions by inhibiting leukocyte extravasation [4, 9, 10]. However, therapeutic intervention, particularly with non-selective alpha-4 blockers, carries risks such as progressive multifocal leukoencephalopathy (PML) due to impaired immune surveillance [10, 14].

Other names

CD49dITGA4Integrin subunit alpha 4Very late antigen-4 (VLA-4)Lymphocyte Peyer patch adhesion molecule (LPAM-1)Integrin alpha-4-beta-1Integrin alpha-4-beta-7

Antagonism of the alpha-4 subunit or its specific heterodimers (alpha-4-beta-1 and alpha-4-beta-7) prevents the interaction between leukocytes and endothelial cell ligands such as VCAM-1 and MAdCAM-1. This blockade inhibits the tethering, rolling, and firm adhesion of leukocytes to the vascular wall, thereby preventing their extravasation and migration into inflamed tissues like the central nervous system and the gastrointestinal tract [1, 4, 15].