The involvement of CD146 and its novel ligand galectin-1 in apoptotic regulation of endothelial cells

Abstract

CD146 is a highly glycosylated junctional adhesion molecule, expressed on human vascular endothelial cells and involved in the control of vessel integrity. Galectin-1 is a lectin produced by vascular cells that can bindsN- andO-linked oligosaccharides of cell membrane glycoproteins. Because both CD146 and Galectin- 1 are involved in modulation of cell apoptosis, we hypothesized that Galectin-1 could interact with CD146, leading to functional consequences in endothelial cell apoptosis. We first characterized CD146 glycosylations and showed that it is mainly composed of N-glycans able to establish interactions with Galectin-1. We demonstrated a sugar-dependent binding of recombinant CD146 to Galectin-1 using both ELISA and Biacore assays. This interaction is direct, with a KD of 3.10-7 M, and specific as CD146 binds to Galectin-1 and not to Galectin-2. Moreover, co-immunoprecipitation experiments showed that Galectin-1 interacts with endogenous CD146 that is highly expressed by HUVEC. We observed a Galectin-1-induced HUVEC apoptosis in a dose-dependent manner as demonstrated by Annexin-V/7AAD staining. Interestingly, both downregulation of CD146 cell surface expression using siRNA and antibody-mediated blockade of CD146 increase this apoptosis. Altogether, our results identify Galectin-1 as a novel ligand for CD146 and this interaction protects, in vitro, endothelial cells against apoptosis induced by Galectin-1. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.