Loss of p47^phox Subunit Enhances Susceptibility to Biomechanical Stress and Heart Failure due to Dysregulation of Cortactin and Actin Filaments

Abstract

Rationale: The classical phagocyte NADPH oxidase (gp91^phox or Nox2) is expressed in the heart. Nox2 activation requires membrane translocation of the p47^phox subunit and is linked to heart failure. We hypothesized that loss of p47^phox subunit will result in decreased ROS production and resistance to heart failure.

Objective: To define the role of p47^phox in pressure-overload induced biomechanical stress.

Methods and Results: Eight weeks old male p47^phox null (p47^phoxKO), Nox2 null (Nox2KO) and wildtype (WT) mice were subjected to transverse aortic constriction (TAC)-induced pressure-overload. Contrary to our hypothesis, p47^phoxKO mice showed markedly worsened systolic dysfunction in response to pressure-overload at 5 weeks and 9 weeks post-TAC compared to WT-TAC mice. We found that biomechanical stress upregulated N-cadherin and β-catenin in p47^phoxKO hearts but disrupted the actin filament cytoskeleton and reduced phosphorylation of FAK. p47^phox interacts with cytosolic cortactin by co-immunoprecipitation and double immunofluorescence staining in murine and human hearts and translocated to the membrane upon biomechanical stress where cortactin interacted with N-cadherin resulting in adaptive cytoskeletal remodeling. However, p47^phoxKO hearts showed impaired interaction of cortactin with N-cadherin resulting in loss of biomechanical stress-induced actin polymerization and cytoskeletal remodeling. In contrast, Nox2 does not interact with cortactin and Nox2 deficient hearts were protected from pressure-overload induced adverse myocardial and intracellular cytoskeletal remodeling.

Conclusions: We showed a novel role of p47^phox subunit beyond and independent of NADPH oxidase activity, as a regulator of cortactin and adaptive cytoskeletal remodeling leading to a paradoxical enhanced susceptibility to biomechanical stress and heart failure.