Integrin alpha-9 beta-1 and Integrin alpha-4 beta-1 (α9β1 and α4β1)

Integrins α9β1 and α4β1 are closely related members of the β1 integrin subfamily that function as transmembrane heterodimeric receptors [1, 2]. They play critical roles in mediating cell-cell and cell-extracellular matrix interactions, primarily through binding to ligands such as vascular cell adhesion molecule-1 (VCAM-1), osteopontin, and tenascin-C [1, 3, 11]. While α4β1 (also known as VLA-4) is well-characterized for its role in leukocyte trafficking and is a validated target in multiple sclerosis and Crohn's disease, α9β1 is increasingly recognized for its involvement in lymphangiogenesis, neutrophil migration, and cancer metastasis [1, 9, 10]. Both integrins are essential for the recruitment of inflammatory cells to sites of injury or disease, making them attractive targets for treating autoimmune and inflammatory disorders [7, 12]. Pharmacological inhibition of these receptors, such as with the monoclonal antibody natalizumab or small-molecule antagonists like firategrast, aims to block leukocyte extravasation and reduce tissue inflammation [5, 13, 16]. However, therapeutic targeting of α4β1 is associated with significant safety concerns, most notably the risk of progressive multifocal leukoencephalopathy (PML) due to impaired CNS immune surveillance [1, 16].

Other names

VLA-4 (Very late antigen-4)CD49d/CD29ITGA4/ITGB1ITGA9/ITGB1Alpha-4 beta-1 and Alpha-9 beta-1 integrins

Antagonism of ligand binding (e.g., VCAM-1, fibronectin, osteopontin) to inhibit leukocyte adhesion, extravasation, and migration into inflamed tissues.