The role of srGAP2 in the regulation of endothelial function

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Endothelial cells create new blood vessels during vasculogenesis and angiogenesis, which are regulated by the binding between the vascular endothelial growth factors (VEGFs) with their receptors (VEGFRs). The two VEGFRs most important in vasculogenesis and angiogenesis are VEGFR2 and VEGFR1. VEGFR2 has been widely studied; it forms homodimers or heterodimers with VEGFR1 and transduces the signal more efficiently than VEGFR1. However, the function of VEGFR1 alone in angiogenesis is poorly understood. This study sought to identify novel interactors specifically involved in the VEGFR1 pathway. Previous work from my lab identified the Rho GAP slit-ROBO GTPase Activating Protein 2 (srGAP2) as an interactor of VEGFR1. Therefore, my study also sought to characterise the partnership between VEGFR1 and srGAP2 and its common signalling pathway in endothelial cells through the identification of new srGAP2 binding partners.
Despite this previous work, I was unable to find a conclusive role for srGAP2 in VEGFR1 signalling. Instead, I showed that srGAP2 plays a role in the maintenance and recovery of the endothelial barrier after the stimulation with three permeability factors; thrombin, TNF-α and angiotensin II. Depletion of srGAP2 enhances endothelial permeability and slows down the recovery of the endothelial monolayer after its stimulation. Moreover, a RhoA activation assay shows an increase in the activation of RhoA that persists longer over time after thrombin stimulation in srGAP2-depleted cells. These results are in accord with experiments in endothelial cells, in which depletion of srGAP2 delayed cell respreading after the thrombin-induced contraction. Interestingly, srGAP2 was found not to be involved in general cell spreading. Therefore, srGAP2 shuts down RhoA signalling after thrombin-induced permeability, inducing a prompt cell respreading and then, the recovery of the endothelial barrier. Further work will be needed to elucidate whether srGAP2 also regulates the RhoA family members RhoB and RhoC.
Date of Award28 Sep 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorHarry H Mellor (Supervisor) & Simon C Satchell (Supervisor)

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