1 Identification of PDCL3 as a novel chaperone protein involved in the generation of functional VEGFR-2 Srimathi Srinivasan 1 , Rosana D Meyer 1 , Ricardo Lugo 1 , Nader Rahimi 1 1 Departments of Pathology and Ophthalmology, Boston University School of Medicine, Boston MA 02118 Corresponding author: Nader Rahimi, Department of Pathology, Boston University Medical Campus, 670 Albany St., Room 510, Boston, MA 02118, Tel: 617-638-5011, Fax: 617-414-7914, E-mail: nrahimi@bu.edu. Running title: PDCL3 controls VEGFR-2 expression The authors declare no conflict of interest. Acknowledgement: This work was supported in part through grants from the National Institute of Health (NIH/NEI) to NR. This work was also supported by a grant from the Department of Pathology, Boston University and by a grant from the Massachusetts Lions Foundation to the Department of Ophthalmology, Boston University. The authors greatly appreciate Cheryl Chi for proof reading the manuscript. Background: Angiogenesis is primarily driven by the VEGF-induced activation of VEGFR-2. Results: We have identified phosducin like 3 as a novel chaperone protein involved in angiogenesis by regulating expression of VEGFR-2. Conclusion: PDCL3 activity is required for angiogenesis. Significance: Targeting PDCL3 may represent an attractive therapeutic strategy to block angiogenesis and tumor growth. Abstract: Angiogenesis, a hallmark step in tumor metastasis and ocular neovascularization, is primarily driven by the function of VEGF ligand on one of its receptors, VEGFR-2. Central to endothelial cells’ proliferation and ensuing angiogenesis, the abundance of VEGFR-2 on the surface of endothelial cells is essential for VEGF to recognize and activate VEGFR-2. We have identified phosducin like 3 (PDCL3, also known as PhLP2A), through a yeast two-hybrid system, as a novel protein involved in the stabilization of VEGFR-2 by serving as a chaperone. PDCL3 binds to the juxtamembrane domain of VEGFR-2 and controls the abundance of VEGFR- 2 by inhibiting its ubiquitination and degradation. PDCL3 increases VEGF- induced tyrosine phosphorylation and is required for VEGFR-2-dependent endothelial capillary tube formation and proliferation. Taken together, our data provide strong evidence for the role of PDCL3 in angiogenesis and establishes the molecular mechanism by which it regulates VEGFR-2 expression and function. Introduction: Angiogenesis is one of the hallmarks of cancer progression and is associated with various other human diseases ranging from neovascular age-related macular degeneration (AMD) to inflammation (1-3). The vast majority of tumors’ growth highly depends on the recruitment of functional blood vessels; tumors unable to induce successful angiogenesis remain dormant. The transition of tumor cells from a pre-vascular to a highly growing and vascularized mass is determined by shift in the balance of expression of pro-angiogenic factors, favoring endothelial cell growth (4). Receptor tyrosine kinases (RTKs) constitute critical machinery of the http://www.jbc.org/cgi/doi/10.1074/jbc.M113.473173 The latest version is at JBC Papers in Press. Published on June 21, 2013 as Manuscript M113.473173 Copyright 2013 by The American Society for Biochemistry and Molecular Biology, Inc. by guest on March 5, 2016 http://www.jbc.org/ Downloaded from