Deglucosylation of N-linked glycans is an important step in the dissociation of calreticulin–class I–TAP complexes
AUTOR(ES)
Van Leeuwen, Jeroen E. M.
FONTE
The National Academy of Sciences of the USA
RESUMO
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 β2 microglobulin 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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=19483Documentos Relacionados
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