alpha4beta1

Alpha4beta1 integrin, also known as very late antigen-4 (VLA-4) or CD49d/CD29, is a transmembrane glycoprotein belonging to the integrin family of cell adhesion molecules. Integrins are heterodimeric proteins composed of non-covalently associated alpha and beta subunits, which mediate cell-extracellular matrix (ECM) and cell-cell interactions essential for various physiological processes.

The alpha4beta1 integrin specifically binds to fibronectin and vascular cell adhesion molecule-1 (VCAM-1), facilitating cell adhesion, migration, and signaling. Its primary ligands include the extracellular matrix protein fibronectin (particularly the CS-1 region) and the immune cell adhesion molecule VCAM-1, which is expressed on activated endothelial cells. This binding is critical in immune cell trafficking, particularly for lymphocytes, monocytes, and eosinophils, during inflammation and immune responses.

Alpha4beta1 plays a key role in lymphocyte homing to secondary lymphoid organs, such as lymph nodes and Peyer’s patches, by interacting with high endothelial venules (HEVs). It also contributes to the migration of immune cells into inflamed tissues, where VCAM-1 is upregulated on endothelial cells. Additionally, alpha4beta1 is involved in the adhesion and migration of hematopoietic stem cells and certain cancer cells, influencing tumor metastasis and progression.

Genetically, the alpha4 subunit is encoded by the *ITGA4* gene, while the beta1 subunit is encoded by the *ITGB1* gene. Mutations or dysregulation in alpha4beta1 have been linked to various disorders, including leukocyte adhesion deficiency type III (LAD-III), a rare genetic condition characterized by impaired immune cell migration and recurrent infections. Therapeutically, monoclonal antibodies targeting alpha4beta1, such as natalizumab and vedolizumab, are used to modulate immune responses in diseases like multiple sclerosis and inflammatory bowel disease.

In summary, alpha4beta1 integrin is a multifunctional adhesion molecule with critical roles in immune cell trafficking, tissue remodeling, and disease pathogenesis. Its targeted inhibition represents a promising approach in treating autoimmune and inflammatory disorders.