Deglucosylation of N-Linked Glycans is an Important Step in the Dissociation of Calreticulin-Class I-TAP Complexes

• Published in: Proceedings of the National Academy of Sciences - PNAS 1996-11, Vol.93 (24), p.13997-14001
• Main Authors: Jeroen E. M. Van Leeuwen, Kearse, Kelly P.
• Format: Article
• Language: English
• Subjects: Animals; Antibodies; ATP Binding Cassette Transporter, Subfamily B, Member 2; ATP-Binding Cassette Transporters - isolation & purification; ATP-Binding Cassette Transporters - metabolism; Autoantigens - isolation & purification; Autoantigens - metabolism; Biological Sciences; Calcium-Binding Proteins - isolation & purification; Calcium-Binding Proteins - metabolism; Calnexin; Calreticulin; Cellular biology; Cellular metabolism; Endoplasmic Reticulum - immunology; Glycoproteins; Glycosylation; H-2 Antigens - biosynthesis; H-2 Antigens - isolation & purification; H-2 Antigens - metabolism; Immunity (Disease); Kinetics; Mice; Mice, Inbred C57BL; Molecules; Polysaccharides; Protein Binding; Protein digestion; Protein metabolism; Proteins; Ribonucleoproteins - isolation & purification; Ribonucleoproteins - metabolism; Spleen - immunology; T lymphocytes; T-Lymphocytes - immunology; Transplantation immunology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.93.24.13997

Recent evidence indicates that newly synthesized major histocompatibility complex (MHC) class I proteins interact with calnexin, a transmembrane endoplasmic reticulum protein specific for certain glycoproteins bearing monoglucosylated glycans. Here, we studied the association of newly synthesized class I proteins with calreticulin, a soluble calnexin-related ER protein, in murine T cells. We found that, unlike calnexin-class I interactions, calreticulin assembly with class I proteins was markedly decreased in the absence of β2microglobulin expression and that calreticulin associated with a subset of class I glycoforms distinct from those assembled with calnexin but similar to those bound to TAP (transporter associated with antigen processing) proteins. Finally, these studies show that deglucosylation of N-linked glycans is important for dissociation of class I proteins from both calreticulin and TAP and that the vast majority of newly synthesized class I proteins associated with calreticulin are simultaneously assembled with TAP. The data demonstrate that calnexin and calreticulin chaperones assemble with distinct MHC class I assembly intermediates in the ER and show that glycan processing is functionally coupled to release of MHC class I proteins from peptide transport molecules.