Cerebral cavernous malformations (CCMs) are vascular malformations that affect the central nervous system and result in cerebral hemorrhage, seizure and stroke. CCMs arise from loss-of-function mutations in one of three genes: KRIT1 (also known as CCM1), CCM2 or PDCD10 (also known as CCM3). PDCD10 mutations in humans often result in a more severe form of the disease relative to mutations in the other two CCM genes, and PDCD10-knockout mice show severe defects, the mechanistic basis for which is unclear. We have recently reported that CCM3 regulates exocytosis mediated by the UNC13 family of exocytic regulatory proteins. Here, in investigating the role of endothelial cell exocytosis in CCM disease progression, we found that CCM3 suppresses UNC13B- and vesicle-associated membrane protein 3 (VAMP3)-dependent exocytosis of angiopoietin 2 (ANGPT2) in brain endothelial cells. CCM3 deficiency in endothelial cells augments the exocytosis and secretion of ANGPT2, which is associated with destabilized endothelial cell junctions, enlarged lumen formation and endothelial cell–pericyte dissociation. UNC13B deficiency, which blunts ANGPT2 secretion from endothelial cells, or treatment with an ANGPT2-neutralizing antibody normalizes the defects in the brain and retina caused by endothelial-cell-specific CCM3 deficiency, including the disruption of endothelial cell junctions, vessel dilation and pericyte dissociation. Thus, enhanced secretion of ANGPT2 in endothelial cells contributes to the progression of CCM disease, providing a new therapeutic approach for treating this devastating pathology.
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Unc13B-deficient mice were a gift from N. Brose (Max Planck Institute of Experimental Medicine, Germany). We thank J. Pober, R. Liu and T. Manes for reagents and discussion. This work was partly supported by US National Institutes of Health (NIH) grants R01 HL109420 (W.M.), HL115148 (W.M.), GM109487 (D.W.), National Natural Science Foundation of China (no. 91539110) (W.M.), CT Stem Cell Innovation (Established Investigator Grant) award no. 14-SCB-YALE-17 (W.M.) and 2016YFC1300600 (W.M.), Scientific Grants of Guangdong (no. 2015B020225002 and 2015A050502018) (W.M.), and American Heart Association grants 13SDG17110045 (H.Z.) and 14SDG20490020 (W.T.).
G.F. and M.Y. are employees of Genentech. W.J. is an employee of Guangzhou Darron Medscience.
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Zhou, H., Qin, L., Zhang, H. et al. Endothelial exocytosis of angiopoietin-2 resulting from CCM3 deficiency contributes to cerebral cavernous malformation. Nat Med 22, 1033–1042 (2016). https://doi.org/10.1038/nm.4169
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