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Circulation. 2014 Feb 25;129(8):864-74. doi: 10.1161/CIRCULATIONAHA.113.004581. Epub 2013 Nov 22.

Mammalian target of rapamycin complex 2 (mTORC2) coordinates pulmonary artery smooth muscle cell metabolism, proliferation, and survival in pulmonary arterial hypertension.

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Pulmonary, Allergy & Critical Care Division (D.A.G., T.V.K., H.Z., H.D., V.P.K., S.M.K., E.A.G.), Department of Pathology and Laboratory Medicine (K.I.-S.), Pulmonary Vascular Disease Program (K.I.-S., H.D., V.P.K., S.M.K., E.A.G.), Center for Clinical Epidemiology and Biostatistics (S.M.K.), and Abramson Cancer Center (V.P.K.), Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA; Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Denver, Aurora, CO (R.M.T.); and Division of Pulmonary, Allergy and Critical Care Medicine, Vascular Medicine Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA (D.A.G., T.V.K.). Dr Goncharova's current affiliation is the Division of Pulmonary, Allergy and Critical Care Medicine, Vascular Medicine Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA.



Enhanced proliferation, resistance to apoptosis, and metabolic shift to glycolysis of pulmonary arterial vascular smooth muscle cells (PAVSMCs) are key pathophysiological components of pulmonary vascular remodeling in idiopathic pulmonary arterial hypertension (PAH). The role of the distinct mammalian target of rapamycin (mTOR) complexes mTORC1 (mTOR-Raptor) and mTORC2 (mTOR-Rictor) in PAVSMC proliferation and survival in PAH and their therapeutic relevance are unknown.


Immunohistochemical and immunoblot analyses revealed that mTORC1 and mTORC2 pathways are markedly upregulated in small remodeled pulmonary arteries and isolated distal PAVSMCs from subjects with idiopathic PAH that have increased ATP levels, proliferation, and survival that depend on glycolytic metabolism. Small interfering RNA- and pharmacology-based analysis showed that although both mTORC1 and mTORC2 contribute to proliferation, only mTORC2 is required for ATP generation and survival of idiopathic PAH PAVSMCs. mTORC2 downregulated the energy sensor AMP-activated protein kinase, which led to activation of mTORC1-S6 and increased proliferation, as well as a deficiency of the proapoptotic protein Bim and idiopathic PAH PAVSMC survival. NADPH oxidase 4 (Nox4) protein levels were increased in idiopathic PAH PAVSMCs, which was necessary for mTORC2 activation, proliferation, and survival. Nox4 levels and mTORC2 signaling were significantly upregulated in small pulmonary arteries from hypoxia-exposed rats at days 2 to 28 of hypoxia. Treatment with the mTOR kinase inhibitor PP242 at days 15 to 28 suppressed mTORC2 but not Nox4, induced smooth muscle-specific apoptosis in small pulmonary arteries, and reversed hypoxia-induced pulmonary vascular remodeling in rats.


These data provide a novel mechanistic link of Nox4-dependent activation of mTORC2 via the energy sensor AMP-activated protein kinase to increased proliferation and survival of PAVSMCs in PAH, which suggests a new potential pathway for therapeutic interventions.


AMP-activated protein kinase; energy metabolism; idiopathic pulmonary arterial hypertension; mTORC2; muscle, smooth, vascular; remodeling; signal transduction

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