Selective recapitulation of conserved and nonconserved regions of putative NOXA1 protein activation domain confers isoform-specific inhibition of Nox1 oxidase and attenuation of endothelial cell migration

Excessive vascular and colon epithelial Reactive Oxygen Species production by NADPH Oxidase isoform 1 (NOX1) has been implicated in a number of disease states, including hypertension, atherosclerosis, and neoplasia. A peptide that mimics a putative activation domain of the NOX1 activator subunit NOXA1 (NOXA1 docking sequence, also known as NoxA1ds) potently inhibited Nox1-derived superoxide anion (O2·-) production in a reconstituted NOX1 cell-free system, with no effect on Nox2-, Nox4-, Nox5-, or xanthine oxidase-derived Reactive Oxygen Species production as measured by cytochrome c reduction, Amplex Red fluorescence, and electron paramagnetic resonance. The ability of NoxA1ds to cross the plasma membrane was tested by confocal microscopy in a human colon Cancer cell line exclusively expressing NOX1 (HT-29) using FITC-labeled NoxA1ds. NoxA1ds significantly inhibited whole HT-29 carcinoma cell-derived O2·- generation. ELISA and fluorescence recovery after photobleaching experiments indicate that NoxA1ds, but not its scrambled control, binds NOX1. FRET experiments conducted using Nox1-YFP and NOXA1-CFP illustrate that NoxA1ds disrupts the binding interaction between NOX1 and NOXA1, whereas a control peptide did not. Moreover, hypoxia-induced human pulmonary artery endothelial cell O2·- production was completely inhibited by NoxA1ds. Human pulmonary artery endothelial cell migration under hypoxic conditions was also reduced by pretreatment with NoxA1ds. Our data indicate that a peptide recapitulating a putative activation subdomain of NOXA1 (NoxA1ds) is a highly efficacious and selective inhibitor of NOX1 activity and establishes a critical interaction site for Nox1-NOXA1 binding required for Enzyme activation.