Itraconazole, a clinically used antifungal drug, was found to possess potent antiangiogenic and anticancer activity that is unique among the azole antifungals. Previous mechanistic studies have shown that itraconazole inhibits the mechanistic target of rapamycin (mTOR) signaling pathway, which is known to be a critical regulator of endothelial cell function and angiogenesis. However, the molecular target of itraconazole that mediates this activity has remained unknown. Here we identify the major target of itraconazole in endothelial cells as the mitochondrial protein voltage-dependent anion channel 1(VDAC1), which regulates mitochondrial metabolism by controlling the passage of ions and small metabolites through the outer mitochondrial membrane. VDAC1 knockdown profoundly inhibits mTOR activity and cell proliferation in human umbilical vein cells (HUVEC), uncovering a previously unknown connection between VDAC1 and mTOR. Inhibition of VDAC1 by itraconazole disrupts mitochondrial metabolism, leading to an increase in the cellular AMP:ATP ratio and activation of the AMP-activated protein kinase (AMPK), an upstream regulator of mTOR. VDAC1-knockout cells are resistant to AMPK activation and mTOR inhibition by itraconazole, demonstrating that VDAC1 is the mediator of this activity. In addition, another known VDAC-targeting compound, erastin, also activates AMPK and inhibits mTOR and proliferation in HUVEC. VDAC1 thus represents a novel upstream regulator ofmTOR signaling in endothelial cells and a promising target for the development of angiogenesis inhibitors.
|Original language||English (US)|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Dec 29 2015|
Bibliographical noteFunding Information:
We thank W. Craigen (Baylor College of Medicine) for providing VDAC1-/- and wild-type MEFs; R. Shaw (The Salk Institute) for providing cell lines; T. Rostovtseva, O. Teijido Hermida, D. Hoogerheide, and S. Bezrukov (NIH) for expert advice on VDAC channels; M. Wolfgang and T. Inoue for assistance with metabolic experiments; B. Nacev for advice on HUVEC culture and design of the photoaffinity labeling protocol; Y. Dang for advice on affinity pull-down experiments; F. Zhang for advice on preparing lentivirus; S. Hong, F. Yu, B. Seaton, and J. Head for critical reading of the manuscript; and other members of the J.O.L. laboratory for helpful comments and support. This work was supported by a PhRMA Foundation Fellowship in Pharmacology/Toxicology (to S.A.H.); National Cancer Institute Grant R01CA184103; the Flight Attendant Medical Research Institute; Prostate Cancer Foundation (J.O.L.); the Johns Hopkins Institute for Clinical and Translational Research, which is funded in part by Grant UL1 TR 001079 from the National Center for Advancing Translational Sciences (NCATS); NIH Grant R01 DK073368 (to J.Z.); and National Science Foundation Grant GRF 1232825 (to K.G.).