Stabilization of VEGFR2 Signaling by Cerebral Cavernous Malformation 3 Is Critical for Vascular Development

Abstract

Cerebral cavernous malformations (CCMs) are human vascular malformations caused by mutations in three genes of unknown function: CCM1, CCM2, and CCM3. CCM3, also known as PDCD10 (programmed cell death 10), was initially identified by its mRNA induction by apoptotic stimuli in vitro. However, the in vivo function of CCM3 has not been determined. Here, we describe mice with a deletion of the CCM3 gene either ubiquitously or specifically in certain cell types, including the vascular endothelium, smooth muscle cells, and neurons. Mice with global or endothelial cell-specific deletion of CCM3 die at embryonic stage, exhibiting defects in embryonic angiogenesis. CCM3 deletion reduces VEGFR2 signaling in embryos and derived endothelial cells. CCM3 is recruited to and stabilizes VEGFR2 in response to stimulation by VEGF, and the C-terminal domain of CCM3 is required for the stabilization of VEGFR2. Indeed, the CCM3 mutants found in human patients with a deletion of the C-terminal domain were labile, and unable to stabilize and activate VEGFR2. These results demonstrate that CCM3 regulates vascular development by modulating VEGFR2 signaling.

Mutations in 2 distinct genetic pathways result in cerebral cavernous malformations in mice

“…Several reports suggest an essential role for binding GCKIII family serine-threonine kinases (16,(21)(22)(23). However, a recent characterization of mice carrying a different conditional allele of Pdcd10 showed that the loss of Pdcd10 in endothelial cells substantially blocks VEGFR2 signaling and inhibits the earliest stages of developmental angiogenesis (47). The implication of VEGFR2 signaling through MAP kinases agrees with a previous report linking GCKIII kinases and ERK signaling (20).…”

Endothelial Cell-to-Cell Junctions: Adhesion and Signaling in Physiology and Pathology

“…This is the case for global mutation of CCM1, -2, and -3 (Whitehead et al 2004;Boulday et al 2009;He et al 2010), Rap1b (ChrzanowskaWodnicka et al 2008, and DEP-1 . In addition, desmoplakin KO produced endothelial alterations in the mouse embryo, besides multi-tissue dysfunctions (Gallicano et al 2001).…”

“…Endothelial-specific and inducible models of null mutations have been described more recently (Pitulescu et al 2010) for CCM2 and CCM3 (Boulday et al 2009;He et al 2010) and Afadin (Tawa et al 2010). The constitutive and endothelial-specific mutation of each CCM gene induces a phenotype superimposable to the constitutive global one, further pointing to a crucial role of CCM molecules in vessels morphogenesis and functions (see below for further discussion).…”

“…The expression of the corresponding proteins is not endothelial specific. However, strong evidence has accumulated indicating that the cause of the pathology is indeed the mutation of the endothelial protein (Boulday et al 2009;He et al 2010). The three CCM genes codify for unrelated proteins that can form a complex (Labauge et al 2007) in which CCM2 bridges CCM1 and CCM3 together.…”

CCM1 and the second life of proteins in adhesion complexes

“…44 Also for Ccm3, both constitutive and tissue-specific deletion gave similar phenotypes. 50 Mice with heterozygous knockout of Ccm1 or Ccm2 do not develop CCMlike vascular lesions in the brain with any useful frequency, which makes these mice unsuitable to study CCM pathogenesis. Because of the suggestions of a two-hit hypothesis for the disease phenotype of CCM patients, other mice studies used mice lacking either p53 51 or Msh2 52 in addition to heterozygosity of CCM1.…”