Cell surface counter receptors are essential components of the unconventional export machinery of galectin-1

• Main Authors: Seelenmeyer, Claudia (Author), Wegehingel, Sabine (Author), Tews, Ivo (Author), Künzler, Markus (Author), Aebi, Markus (Author), Nickel, Walter (Author)
• Format: Article
• Language: English
• Published: 2005-10-24.
• Subjects: Article
• Online Access: Get fulltext

 Galectin-1 is a component of the extracellular matrix as well as a ligand of cell surface counter receptors such as beta-galactoside-containing glycolipids, however, the molecular mechanism of galectin-1 secretion has remained elusive. Based on a nonbiased screen for galectin-1 export mutants we have identified 26 single amino acid changes that cause a defect of both export and binding to counter receptors. When wild-type galectin-1 was analyzed in CHO clone 13 cells, a mutant cell line incapable of expressing functional galectin-1 counter receptors, secretion was blocked. Intriguingly, we also find that a distant relative of galectin-1, the fungal lectin CGL-2, is a substrate for nonclassical export from Chinese hamster ovary (CHO) cells. Alike mammalian galectin-1, a CGL-2 mutant defective in beta-galactoside binding, does not get exported from CHO cells. We conclude that the beta-galactoside binding site represents the primary targeting motif of galectins defining a galectin export machinery that makes use of beta-galactoside-containing surface molecules as export receptors for intracellular galectin-1.