Regulation and Function of Cerebral Cavernous Malformation Proteins Public Deposited

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  • March 20, 2019
  • Borikova, Asya Lazarova
    • Affiliation: School of Medicine, Department of Pharmacology
  • Cerebral Cavernous Malformations (CCM) is a genetic disease that causes dilated, leaky blood vessels in the brain and manifests with neurological deficits, seizures and hemorrhagic stroke. CCM is linked with loss-of-function mutations in ccm1, ccm2, and ccm3. CCM1, 2 and 3 are adaptor-like proteins that form a ternary complex, which has suggested that they regulate a common molecular pathway for the maintenance of endothelial cell function. We provide subcellular localization evidence in support of a common molecular role for CCM1 and 2, and define the only two known signaling pathways that are coordinately regulated by CCM1, 2 and 3. Using molecular and functional approaches, we report that 433MISDISSDIEAL444 is a nuclear export sequence in CCM2, the localization of CCM1 patterns that of wildtype and nuclear export deficient CCM2 and that the cytosolic localization of CCM2 is required for normal endothelial function. Regulated co-localization of CCM1 and CCM2 within the same subcellular compartment is consistent with a common function for CCM1 and 2. Consistent with these observations a finding from Crose et al. showed that CCM2 binds the E3 ubiquitin ligase Smurf1 and localizes Smurf1 to sites of RhoA at the plasma membrane for the degradation of RhoA. We utilized molecular, FRET-based biosensor, biophysical and functional approaches to define that CCM1, 2 and 3 co-regulate the abundance and activity of RhoA and RhoA-dependent cytoskeletal dynamics and endothelial cell self-assembly in lumen-like tubes. We show that pharmacological and genetic inhibition of ROCK rescues the functional defects in CCM and propose ROCK as a potential therapeutic target for CCM. Using genetic, proteomic and functional approaches we also define that CCM1, 2 and 3 co-regulate the abundance and activity of the small GTPase Rap1, and demonstrate a novel interaction between CCM2 and the E3 ubiquitin ligase Smurf2. Smurf2 regulates the degradation of Rap1 in neurons and we propose that CCM1, 2 and 3 co-regulate Rap1 abundance and activity for the regulation of endothelial cell tube formation. The studies presented here provide evidence that CCM1,2 and 3 coordinately regulate RhoA and Rap1, two key signaling hubs for the maintenance of endothelial function and vascular repair.
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  • Johnson, Gary
  • Doctor of Philosophy
Graduation year
  • 2012

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