Integrin alpha 7 beta 1, also called VLA‑7 (very late antigen‑7), is the major laminin‑binding integrin in cardiac and skeletal muscle (1‑4). The non‑covalent heterodimer is composed of ~150 kDa alpha 7 and 130 kDa beta 1/CD29 type I transmembrane glycoprotein subunits with short cytoplasmic tails (2). While alpha 7 pairs only with beta 1, twelve integrins share the beta 1 subunit (1‑5). The longest version of alpha 7 is the X1X2B form, encoding 1179 amino acids (aa). Six alternatively spliced 1116‑1160 aa isoforms of the alpha 7 subunits have short extracellular (X1, X2) or cytoplasmic (A, C) deletions. Isoforms are differentially expressed by tissue and developmental stage and may show preferences for specific laminins (3‑5). The beta 1 vWFA domain participates with the alpha 7 FG‑GAP motifs in ligand binding. The alpha 7 subunit is cleaved into extracellular heavy and transmembrane/cytoplasmic light chains (3). The mouse alpha 7 heavy chain shares 89%, 90%, 87% and 85% aa sequence identity with human, rat, feline and bovine alpha 7, and the mouse beta 1 ECD shares 98% aa identity with rat and 93‑94% with human, bovine, porcine, ovine, canine and feline beta 1. The alpha 7 heavy chain in species other than mouse may also be cleaved at aa 603‑605 by a serine protease; fragments remain associated. This form enhances the active, unfolded and open conformation, promoting cell adhesion and spreading (1, 2, 6). Adhesion of alpha 7 beta 1 to laminin‑111 accounts for many of its effects, but alpha 7 beta 1 also binds most other laminins (5). It protects muscle from exercise‑induced damage, and its absence in humans or mice causes a form of muscular dystrophy (7‑9). alpha 7 beta 1 is also expressed in vascular smooth muscle (VSM), and is important for development of the cerebral vasculature (10). VSM cells show increased alpha 7 beta 1 expression and enhanced laminin binding in injury‑induced atherosclerosis or PDGF treatment (11, 12). Deletion of alpha 7 results in VSM hyperplasia, especially in response to injury (13).
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| Product By Gene ID | 3679 |
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