CCM1 regulates vascular-lumen organization by inducing endothelial polarity

Abstract

SummaryLittle is known about the molecular mechanisms that regulate the organization of vascular lumen. In this paper we show that lumen formation correlates with endothelial polarization. Adherens junctions (AJs) and VE-cadherin (VEC, encoded by CDH5) are required for endothelial apicobasal polarity in vitro and during embryonic development. Silencing of CDH5 gene expression leads to abrogation of endothelial polarity accompanied by strong alterations in lumenal structure. VEC co-distributes with members of the Par polarity complex (Par3 and PKCz) and is needed for activation of PKCz. CCM1 is encoded by the CCM1 gene, which is mutated in 60% of patients affected by cerebral cavernous malformation (CCM). The protein interacts with VEC and directs AJ organization and AJ association with the polarity complex, both in cell-culture models and in human CCM1 lesions. Both VEC and CCM1 control Rap1 concentration at cell-cell junctions. We propose that VEC, CCM1 and Rap1 form a signaling complex. In the absence of any of these proteins, AJs are dismantled, cell polarity is lost and vascular lumenal structure is severely altered.

The Wnt/Planar Cell Polarity Signaling Pathway Contributes to the Integrity of Tight Junctions in Brain Endothelial Cells

“…22 In addition, the apicobasal polarity in endothelial cells was shown to be controlled by VE-cadherin and associated proteins, via activation of the Par/aPKC PCP complex. 28 We confirmed here, by confocal microscopy, that PAR-3 is expressed by hCMEC/D3 cells and partly localized at cell-cell junctions, together with ZO-1, a prototype TJ-associated protein; a proportion of PAR-3 was also detected in the cytosol and nucleus, in line with previous reports in different cell types. 29,30 We established here, by quantitative confocal microscopy analysis of Podxl and P-gp expression in individual cells, that hCMEC/D3 cells are polarized on Transwell inserts (Figure 2), as previously reported by electron microscopy monitoring of P-gp expression.…”

Biomimetic model to reconstitute angiogenic sprouting morphogenesis in vitro

“…These steps are consistent with seminal observations of in vivo angiogenesis showing the emergence of tip cells from an existing vessel, and stalk cells that establish apical/basal polarity and form a lumen that excludes the tip cell (24,25,41). VEGF has been shown to be important in triggering such tip cells to extend thin, actin-rich protrusions and in guiding stalk cells to form elongated multicellular sprouts (5,25).…”

“…For this purpose, we focused on the MVPS cocktail, which promoted the greatest sprouting response with minimal single-cell migration. Before stimulation, cells in the endothelialized channel exhibited the expected apical-basal polarity as demonstrated by the localization of the CD34 apical marker podocalyxin to the luminal face (24). On the basolateral side of the endothelium we observed both laminin and collagen IV deposition, suggestive of a cell-deposited matrix layer enveloping the parent vessel (Fig.…”

Nuclear Localization of Integrin Cytoplasmic Domain-associated Protein-1 (ICAP1) Influences β1 Integrin Activation and Recruits Krev/Interaction Trapped-1 (KRIT1) to the Nucleus

“…Conversely, increased cytoplasmic ICAP1 leads to greater repression of integrin ␤1 activation, and thus general defects in cell adhesion and cell spreading would be expected. This could lead to a loss of endothelial cell polarity and lumen formation (48), phenotypes also seen in CCM patient samples (49). In addition to influencing levels of ICAP1 in the cytoplasm and thus impacting cytoplasmic functions of ICAP1, as discussed further below, nuclear localization FIGURE 8.…”