Localization of phospholipase Cbeta isozymes in the mouse cerebellum

Recent studies demonstrate that processing of N-linked glycans plays an important role in the quality control of major histocompatibility complex (MHC) class I transport from the endoplasmic reticulum (ER) to the Golgi complex and beyond. Here, we investigated the importance of oligosaccharide chain length on the association of MHC class I proteins with molecular chaperones and their intracellular transport from the ER to the Golgi. These data show that calnexin interaction with class I proteins having truncated N-glycans 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 relative to class I proteins bearing typical oligosaccharides. Taken together, these studies show that N-glycan chain length is an important determinant for the quality control of newly synthesized MHC class I proteins in the ER.