Integrin α7β1 is a redox-regulated target of hydrogen peroxide in vascular smooth muscle cell adhesion

Upon adhesion to laminin-111, aortic smooth muscle cells initially form membrane protrusions with an average diameter of 2.9 mu m. We identified these protrusions also as subcellular areas of increased redox potential and protein oxidation by detecting cysteine sulfenic acid groups with dimedone. Hence, we termed these areas oxidative hot spots. They are spatially and temporally transient during an early stage of adhesion and depend on the activity of the H2O2-generating NADPH oxidase 4. Presumably located on cellular protrusions, integrin alpha 7 beta 1 mediates adhesion and migration of vascular smooth muscle cells to laminins of their surrounding basement membrane. Using protein chemistry and mass spectrometry, two specific oxidation sites within the integrin alpha 7 subunit were identified: one located in its genu region and another within its calf 2 domain. Upon H2O2 treatment, two cysteine residues are oxidized thereby unlocking a disulfide bridge. The genu region is a hinge, around which the integrin domains pivot between a bent/inactive and an upright/active conformation. Also, cysteine oxidation within the calf 2 domain permits conformational changes related to integrin activation. H2O2 treatment of alpha 7 beta 1 integrin in concentrations of up to 100 mu M increases integrin binding activity to laminin-111, suggesting a physiological redox regulation of alpha 7 beta 1 integrin. (C) 2012 Elsevier Inc. All rights reserved.