Abstract 13033: Cavin/Caveolin Interaction Modulates BMP/Smad Signaling in Pulmonary Artery Endothelial Cells

Abstract

Background: Pulmonary hypertension (PH) is a progressive disease associated with poor prognosis. Caveolin-1 (Cav1) and Cavin-1 are components of caveolae, and both interact with each other and influence the composition and stabilization of caveolae. Cav1 is identified as a related gene of pulmonary arterial hypertension (PAH). Gene mutation of bone morphogenetic protein type II receptor (BMPRII) is the most common cause of PAH. BMPRII is localized in caveolae and associates with Cav1. However, the role of the Caveolin-Cavin system on the BMP/Smad signaling and the PAH progression has not been well-known. Methods and Results: As in previous reports, Cav1 knockout mice exhibited PH with pulmonary vascular remodeling and right ventricular hypertrophy. Caveolae disappeared in pulmonary microvascular endothelial cells of Cav1 knockout mice. We then examined the role of Caveolin-Cavin and the association with BMP/Smad signaling in human pulmonary artery endothelial cells (hPAECs). Cav1 knockdown in hPAECs reduced BMPRII at the plasma membrane and Smad 1/5/9 phosphorylation. Cav1 knockdown also significantly increased hypoxia-induced apoptosis in hPAECs. Cav1 was associated with BMPRII at the membrane of hPAECs. In addition, Cavin-1 inhibited the interaction of BMPRII with Cav1 and reduced BMPRII localization on the membrane of hPAECs. Cavin-1 knockdown reversed BMPRII localization at the plasma membrane and Smad 1/5/9 phosphorylation induced by Cav1 knockdown. Both Cavin-1 and BMPRII were associated with the Cav1 scaffolding domain. These results suggest that Cavin-1 interacts with Cav1 and inhibits the association of Cav1 with BMPRII, resulting in modulating Smad signaling pathway. Conclusions: Cavin-1 and BMPRII are competitively associated with Cav1 at the plasma membrane and modulating BMP/Smad signal transduction in PAECs. Our findings reveal a previously undescribed mechanism via Cavin-Caveolin interaction in BMP/Smad signaling-modulated PH development.