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 μm. 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 α7β1 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 α7 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 α7β1 integrin in concentrations of up to 100 μM increases integrin binding activity to laminin-111, suggesting a physiological redox regulation of α7β1 integrin.

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► Upon adhesion to laminin-111 vascular smooth muscle cells form “oxidative hot spots.”
► Nox4 enzyme plays an important role in adhesion, migration, and hot spot formation.
► Recombinant α7β1 integrin can be oxidized by H2O2 at cysteine residues.
► Oxidized Cys are in key regions of the integrin involved in conformational changes.
► Treatment of α7β1 with 100 μM H2O2 increases binding activity to laminin-111.