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IQGAP1 causes choroidal neovascularization by sustaining VEGFR2-mediated Rac1 activation

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Abstract

Loss of visual acuity in neovascular age-related macular degeneration (nAMD) occurs when factors activate choroidal endothelial cells (CECs) to transmigrate the retinal pigment epithelium into the sensory retina and develop into choroidal neovascularization (CNV). Active Rac1 (Rac1GTP) is required for CEC migration and is induced by different AMD-related stresses, including vascular endothelial growth factor (VEGF). Besides its role in pathologic events, Rac1 also plays a role in physiologic functions. Therefore, we were interested in a method to inhibit pathologic activation of Rac1. We addressed the hypothesis that IQGAP1, a scaffold protein with a Rac1 binding domain, regulates pathologic Rac1GTP in CEC migration and CNV. Compared to littermate Iqgap1+/+, Iqgap1−/− mice had reduced volumes of laser-induced CNV and decreased Rac1GTP and phosphorylated VEGFR2 (p-VEGFR2) within lectin-stained CNV. Knockdown of IQGAP1 in CECs significantly reduced VEGF-induced Rac1GTP, mediated through p-VEGFR2, which was necessary for CEC migration. Moreover, sustained activation of Rac1GTP induced by VEGF was eliminated when CECs were transfected with an IQGAP1 construct that is unable to bind Rac1. IQGAP1-mediated Src activation was involved in initiating Rac1 activation, CEC migration, and tube formation. Our findings indicate that CEC IQGAP1 interacts with VEGFR2 to mediate Src activation and subsequent Rac1 activation and CEC migration. In addition, IQGAP1 binding to Rac1GTP results in sustained activation of Rac1, leading to CEC migration toward VEGF. Our study supports a role of IQGAP1 and the interaction between IQGAP1 and Rac1GTP to restore CECs quiescence and, therefore, prevent vision-threatening CNV in nAMD.

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Acknowledgements

This work was supported by the National Institutes of Health EY014800 and an Unrestricted Grant from Research to Prevent Blindness, Inc., New York, NY, to the Department of Ophthalmology & Visual Sciences, University of Utah; and the National Institutes of Health R01EY015130 and R01EY017011 to M.E.H and by T32 EY024234 to A. R. D.B.S. is supported by the Intramural Research Program of the National Institutes of Health. We thank Dr. William A. Muller for providing adenovirus-IQGAP1shRNA constructs.

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Authors and Affiliations

  1. The John A Moran Eye Center, University of Utah, 65 Mario Capecchi Drive, Salt Lake City, UT, 84132, USA

    Haibo Wang, Aniket Ramshekar, Eric Kunz & M. Elizabeth Hartnett

  2. Department of Laboratory Medicine, National Institutes of Health, Bethesda, MD, 20892, USA

    David B. Sacks

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  1. Haibo Wang
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HW designed and performed the experiments and wrote the manuscript; AR and EK performed experiments and housed the animals; DBS provided the animals, reagents, and wrote the manuscript; MEH designed the experiments, wrote the manuscript, and provided funding supports.

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Correspondence to M. Elizabeth Hartnett.

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Wang, H., Ramshekar, A., Kunz, E. et al. IQGAP1 causes choroidal neovascularization by sustaining VEGFR2-mediated Rac1 activation. Angiogenesis 23, 685–698 (2020). https://doi.org/10.1007/s10456-020-09740-y

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