Integrin β1 is bound to galectin-1 in human trophoblast

Interaction of sugar binding proteins-galectins, with glycoconjugates is considered relevant for various reproductive processes. Galectin-1 (gal-1) is a molecule involved in trophoblast cell invasion, which is accomplished through interaction with cell surface and/or extracellular matrix glycoproteins. A possibility of interaction of endogenous gal-1 and trophoblast beta(1) integrins, both previously shown relevant for trophoblast invasion, was investigated. Confocal microscopy showed overlap in gal-1 and beta(1) integrin localization at the plasma membrane of isolated cytotrophoblast, HTR-8/SVneo extravillous trophoblast cell line and JAr choriocarcinoma cells. Immunoprecipitation confirmed an interaction of gal-1 with integrin beta(1), but not with alpha(1) or alpha(5) integrin subunits. Nondenaturing electrophoresis and subcellular fractionation suggested association of gal-1 with beta(1) integrin in intracellular and plasma membrane compartments of HTR-8/SVneo cells. Gal-1/beta(1) integrin complex was sensitive to chemical and enzyme treatments, indicating carbohydrate dependent interaction. Down-regulation of gal-1 by siRNA, however, had no effect on level or distribution of beta(1) integrin, as determined by qPCR and flow cytometry. These results suggest complex lectin type interaction of gal-1 with beta(1) integrin at the trophoblast cell membrane, which could influence trophoblast cell adhesion, migration and invasion.