Cerebral Cavernous Malformation Proteins and MEKK3 Coordinately Modulate SMURF1 Abundance to Control RhoA-dependent Endothelial Cell Phenotypic State. Cerebral Cavernous Malformation Proteins and MEKK3 Coordinately Modulate SMURF1 Abundance to Control RhoA-dependent Endothelial Cell Phenotypic State

Cerebral Cavernous Malformations (CCM), caused by loss of CCM1, CCM2 or CCM3 in endothelial cells (ECs), are leaky capillaries causing seizures and stroke. CCM protein loss gives overlapping changes in biomechanical and transcriptional properties of ECs, due to common RhoA-driven alterations in cytoskeletal organization and intracellular signaling. However, EC models of 3-D tube formation show loss of each CCM protein generates distinct morphological defects in tubular structures. Computational modeling, live-cell imaging and RNA sequencing revealed distinct functional roles of CCM1 and CCM3 in regulating EC-EC and EC-matrix interactions. CCM2 has an intermediate phenotype consistent with its interaction with CCM1 and CCM3. In ECs, CCM proteins regulate SMURF1 E3 ligase ubiquitination and degradation of RhoA. Loss of CCM proteins results in loss of SMURF1 and a concomitant increase of MEKK3, a negative regulator of SMURF1 expression. We propose CCM lesions develop because of dysregulated SMURF1 resulting in RhoA and MEKK3 gain-of-function. Overall design: 29 experimental samples with replicates indicated in sample title