Vascular Smooth Muscle Vps34 in Pulmonary Arterial Hypertension - PROJECT SUMMARY (See instructions): Pulmonary arterial hypertension (PAH) is a progressive and rapidly fatal disease with no cure. PAH manifests by remodeling of small pulmonary arteries, leading to increased PA pressure, elevated right ventricular (RV) afterload, heart failure, and death. One of the key components of PA remodeling is the increased proliferation and survival of PA vascular smooth muscle cells (PAVSMC). Recently, I found that activation of Class Ill Phosphatidylinositol 3 kinase/vacuolar protein sorting 34 (Vps34), evidenced by lack of inhibitory phosphorylation at Ser164 (P-S164-Vps34), promotes hyper-proliferation of PAH PAVSMC, which is Akt-dependent and is associated with accumulation of Vps 15, deficiency of TSC2, activation of mammalian target of rapamycin complex 1 (mTOC1), increased growth and proliferation of PAVSMC, and pulmonary vascular remodeling in PAH. Our recent in silico analyses suggested potential protein phosphatases that may be involved in this Akt-dependent Vps34 activation. Similar to human PAH, decreased P-S164-Vps34 was also observed in PA VSM from experimental rodent PH models, which is reversely correlated with increased PA medial thickness, and was associated with increased RV systolic pressure (RVSP) and RV hypertrophy. Further, I show that Vps34 inhibition by siR NA significantly decreased PAH PAVSMC proliferation and survival, reduced Vps15 and restored TSC2 prot4in levels, and inactivated mTORC1. Additionally, our data show that pharmacological inhibition of Vps34 reverses PAH-specific signaling abnormalities, selectively inhibits proliferation and promotes apoptosis in human PAH PAVSMC, and significantly attenuated established pulmonary vascular remodeling and reduced RV hypertrophy in mice with SU5416/hypoxia-induced PH. based on our preliminary data, I hypothesize that Vps34 is activated in PAH PAVSMC in an Akt-dependent manner, leading to increased PAVSMC proliferation and survival, pulmonary vascular remodeling, and PH via modulating Vps15 and TSC2-mTORC1 axis. I also propose that pharmacological inhibition of VPS34 inhibits proliferation and induced apoptosis in PAH PAVSMC, and attenuates or reverses pulmonary vascular remodeling and PH. I will test my hypothesis using three specific aims: Aim 1 will examine the status and mechanisms of Vps34 regulation in PAH pulmonary vasculature, Aim2 will determine the role of Vps34 in human PAVSMC proliferation and survival, and Aim 3 will evaluate whether molecular or pharmacological
