ROLE OF N-GLYCANS ON MEGALIN IN THE LIGAND-BINDING ACTIVITY

摘要

Megalin is a 600 kDa single-spanning transmembrane glycoprotein [1], which is known to be an endocytic receptor. Megalin is distributed not only in the kidney but also in various tissues. Many ligands for megalin have been identified, for example, vitamin-binding proteins such as retinol-binding protein (RBP), carrier proteins such as albumin, and hormones such as parathyroid hormone [2]. Megalin has four ligand-binding domains in the extracellular region, which has 30 potential N-glycosylation sites. It is well documented that different tissues in the body have specific glycoforms of glycoproteins [3]. Thus, megalin likely has tissue-specific glycoforms. We hypothesize that glycans on megalin modify its ligand-binding activity and provide megalin with a specific ligand-binding activity required by each tissue.