α9β1

Integrin α9β1 mediates cell adhesion and migration through extracellular matrix and endothelial ligands, including VCAM-1, which supports neutrophil adhesion and transendothelial migration^[1]. Mechanistically, α9β1 ligation activates Src, p130Cas, Rac1, and inducible nitric oxide synthase, linking its cytoplasmic domain to nitric oxide-dependent cell migration^[2]. In vascular smooth muscle cells, PDGF-BB upregulates α9, while anti-α9 antibody or smooth muscle-specific α9 deletion suppresses synthetic phenotype, proliferation, migration, and injury-induced neointimal hyperplasia through reduced FAK/Src-ERK/p38-GSK3β/β-catenin signaling^[3]. In disease models, α9β1 and ligands such as osteopontin and tenascin-C contribute to autoimmune disease biology, including rheumatoid arthritis and multiple sclerosis models^[4]. In lymphatic biology, EMILIN1-α9β1 interaction supports lymphatic valve formation and maintenance, and α9β1-deficient mice develop fatal bilateral chylothorax^[5][6]. Compared with RGD-binding integrins such as α5β1, α9β1 recognizes non-RGD motifs and uses β1 as its reported partner, supporting isoform-specific experimental design^[3]. For experimental applications, blocking antibodies such as Y9A2 and 55A2C enable α9β1 pathway interrogation in smooth muscle, vascular injury, thrombosis, and inflammation models^[3][7].

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