The glut 1 glucose transporter interacts with calnexin and calreticulin

Calnexin is an integral membrane protein that acts as a chaperone during glycoprotein folding in the endoplasmic reticulum. Cross-linking studies were carried out with the aim of investigating the interactions of calnexin with glycoproteins in vitro, A truncated version of the integral membrane glycoprotein Glut 1 (GT(155)) was synthesized in a rabbit reticulocyte translation system in the presence of canine pancreatic microsomes, Following immunoprecipitation with an anti-calnexin antiserum, a cross-linker-independent association was observed between GT(155) and calnexin. In addition, the anti-calnexin antiserum immunoprecipitated a W-dependent cross-linking product consisting of GT(155) and a protein of approximately 60 kDa designated CAP-60 (calnexin-associated protein of 60 kDa), Both the GT(155)-calnexin and the GT(155)-CAP-60 interactions were dependent on the presence of a correctly modified oligosaccharide group on GT(155), a characteristic of many calnexin interactions, A GT(155) mutant that was not glycosylated (AGGT(155)) did not associate with calnexin or CAP-60, Calreticulin, the soluble homologue of calnexin, was also shown to interact with GT(155) only when the protein bore a correctly modified oligosaccharide group, Thus, our data show that both calnexin and calreticulin with Glut 1 in a glycosylation-dependent manner.