Influence of N-glycan chain length on chaperone association and intracellular transport of major histocompatibility complex class I proteins

Recent studies demonstrate that processing of N-linked glycans plays an imp ortant role in the quality control of major histocompatibility complex (MHC ) class I transport from the endoplasmic reticulum (ER) to the Golgi comple x and beyond. Here, we investigated the importance of oligosaccharide chain length on the association of MHC class I proteins with molecular chaperone s and their intracellular transport from the ER to the Gels. These data sho w that calnexin interaction with class I proteins having truncated N-glycan s was reduced compared to normal class I molecules, whereas the assembly of class I with calreticulin and TAP was unperturbed by N-glycan chain length . Additionally, these results demonstrate that class I proteins containing truncated N-glycans showed decreased detachment from calreticulin and TAP r elative to class I proteins bearing typical oligosaccharides. Taken togethe r, these studies show that N-glycan chain length is an important determinan t for the quality control of newly synthesized MHC class I proteins in the ER. (C) 1999 Academic Press.