Heart of glass anchors Rasip1 at endothelial cell-cell junctions to support vascular integrity
Bart-Jan de Kreuk,
Alexandre R Gingras,
James DR Knight,
Jian J Liu,
Anne-Claude Gingras,
Mark H Ginsberg
Affiliations
Bart-Jan de Kreuk
Department of Medicine, University of California, San Diego, San Diego, United States
Alexandre R Gingras
Department of Medicine, University of California, San Diego, San Diego, United States
James DR Knight
Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
Jian J Liu
Department of Medicine, University of California, San Diego, San Diego, United States
Anne-Claude Gingras
Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Canada
Heart of Glass (HEG1), a transmembrane receptor, and Rasip1, an endothelial-specific Rap1-binding protein, are both essential for cardiovascular development. Here we performed a proteomic screen for novel HEG1 interactors and report that HEG1 binds directly to Rasip1. Rasip1 localizes to forming endothelial cell (EC) cell-cell junctions and silencing HEG1 prevents this localization. Conversely, mitochondria-targeted HEG1 relocalizes Rasip1 to mitochondria in cells. The Rasip1-binding site in HEG1 contains a 9 residue sequence, deletion of which abrogates HEG1’s ability to recruit Rasip1. HEG1 binds to a central region of Rasip1 and deletion of this domain eliminates Rasip1’s ability to bind HEG1, to translocate to EC junctions, to inhibit ROCK activity, and to maintain EC junctional integrity. These studies establish that the binding of HEG1 to Rasip1 mediates Rap1-dependent recruitment of Rasip1 to and stabilization of EC cell-cell junctions.
