| Cerebral cavernous malformations (CCM) are cerebrovascular lesions occurring with homozygous loss of function mutations of CCM1, -2, and -3. CCMs can cause neurological deficits, seizures, and fatal hemorrhagic stroke. Loss of function in any one of the three CCM proteins leads to defects in in vitro angiogenesis assays, along with increased actin stress fibers in endothelial cells. Elevated RhoA and Rho kinase (ROCK)-LIM kinase hyperactivity results upon loss of the CCM proteins, likely from dysregulation of the E3 ubiquitin ligase SMURF1. Phosphorylation of the LIM kinase substrate and actin depolymerizing factor cofilin is increased in primary endothelial cells and surgically resected human CCM lesions, providing a novel biomarker for CCM disease. The CCM phenotype and RhoA-ROCK hyperactivity can be recapitulated in endothelial progenitor-derived endothelial cells, primary cells that can be isolated from the peripheral blood of human CCM patients. Significantly, treatment with structurally distinct small molecule ROCK inhibitors rescues the CCM phenotype in vitro and reverses the hyperactivation of ROCK effectors seen with loss of the CCM proteins. Interrogation of the kinome in endothelial cells with CCM2 knockdown using multiplexed kinase inhibitor beads coupled to mass spectroscopy reveals striking dysregulation, likely multifactorial from loss of the scaffold-like CCM2 protein, dysregulation of SMURF1, and concomitant hyperactivation of the small GTPase RhoA. Of particular interest are the loss of two critical angiogenesis kinases, TIE-2 and BMX. Together, these data provides insight to the molecular mechanism of CCM pathophysiology and provides clues for future successful pharmacological treatment of the disease. |
