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Arterioscler Thromb Vasc Biol. 2006 Sep;26(9):1991-7. Epub 2006 Jun 8.

IQGAP1 mediates VE-cadherin-based cell-cell contacts and VEGF signaling at adherence junctions linked to angiogenesis.

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  • 1Division of Cardiology, Emory University School of Medicine, 1639 Pierce Drive, Atlanta, GA 30322, USA.

Abstract

OBJECTIVE:

Vascular endothelial growth factor (VEGF) induces angiogenesis by stimulating reactive oxygen species (ROS) production primarily through the VEGF receptor-2 (VEGFR2). One of the initial responses in established vessels to stimulate angiogenesis is loss of vascular endothelial (VE)-cadherin-based cell-cell adhesions; however, little is known about the underlying mechanisms. IQGAP1 is a novel VEGFR2 binding protein, and it interacts directly with actin, cadherin, and beta-catenin, thereby regulating cell motility and morphogenesis.

METHODS AND RESULTS:

Confocal microscopy analysis shows that IQGAP1 colocalizes with VE-cadherin at cell-cell contacts in unstimulated human endothelial cells (ECs). VEGF stimulation reduces staining of IQGAP1 and VE-cadherin at the adherens junction without affecting interaction of these proteins. Knockdown of IQGAP1 using siRNA inhibits localization of VE-cadherin at cell-cell contacts, VEGF-stimulated recruitment of VEGFR2 to the VE-cadherin/beta-catenin complex, ROS-dependent tyrosine phosphorylation of VE-cadherin, which is required for loss of cell-cell contacts and capillary tube formation. IQGAP1 expression is increased in a mouse hindlimb ischemia model of angiogenesis.

CONCLUSIONS:

IQGAP1 is required for establishment of cell-cell contacts in quiescent ECs. To induce angiogenesis, it may function to link VEGFR2 to the VE-cadherin containing adherens junctions, thereby promoting VEGF-stimulated, ROS-dependent tyrosine phosphorylation of VE-cadherin and loss of cell-cell contacts.

PMID:
16763158
[PubMed - indexed for MEDLINE]
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