TY - JOUR
T1 - Tapasin enhances assembly of transporters associated with antigen processing-dependent and -independent peptides with HLA-A2 and HLA-B27 expressed in insect cells
AU - Lauvau, Grégoire
AU - Gubler, Brigitte
AU - Cohen, Hélène
AU - Daniel, Soizic
AU - Caillat-Zucman, Sophie
AU - Van Endert, Peter M.
PY - 1999/10/29
Y1 - 1999/10/29
N2 - Assembly of HLA class I-peptide complexes is assisted by multiple proteins that associate with HLa molecules in loading complexes. These include the housekeeping chaperones calnexin and calreticulin and two essential proteins, the transporters associated with antigen processing (TAP) for peptide supply, and the protein tapasin which is thought to act as a specialized chaperone. We dissected functional effects of processing cofactors by co-expressing in insect cells various combinations of the human proteins HLA-A2, HLA-B27, β2-microglobulin, TAP, calnexin, calreticulin, and tapasin. Stability at 37 °C and surface expression of class I dimers correlated closely in baculovirus-infected Sf9 cells, suggesting that these cells retain empty dimers in the endoplasmic reticulum. Both HLA molecules form substantial quantities of stable complexes with insect cell-produced peptide pools. These pools are TAP-selected cytosolic peptides for HLA-B27 but endoplasmic reticulum-derived, i.e. TAP-independent peptides for HLA-A2. This discrepancy may be due to peptide selection by human TAP which is much better adapted to the HLA-B27 than to the HLA-A2 ligand preferences. HLA class I assembly with peptides from TAP-dependent and -independent pools was enhanced strongly by tapasin. Thus, tapasin acts as a chaperone and/or peptide editor that facilitates assembly of peptides with HLA class I molecules independently of mediating their interaction with TAP and/or retention in the endoplasmic reticulum.
AB - Assembly of HLA class I-peptide complexes is assisted by multiple proteins that associate with HLa molecules in loading complexes. These include the housekeeping chaperones calnexin and calreticulin and two essential proteins, the transporters associated with antigen processing (TAP) for peptide supply, and the protein tapasin which is thought to act as a specialized chaperone. We dissected functional effects of processing cofactors by co-expressing in insect cells various combinations of the human proteins HLA-A2, HLA-B27, β2-microglobulin, TAP, calnexin, calreticulin, and tapasin. Stability at 37 °C and surface expression of class I dimers correlated closely in baculovirus-infected Sf9 cells, suggesting that these cells retain empty dimers in the endoplasmic reticulum. Both HLA molecules form substantial quantities of stable complexes with insect cell-produced peptide pools. These pools are TAP-selected cytosolic peptides for HLA-B27 but endoplasmic reticulum-derived, i.e. TAP-independent peptides for HLA-A2. This discrepancy may be due to peptide selection by human TAP which is much better adapted to the HLA-B27 than to the HLA-A2 ligand preferences. HLA class I assembly with peptides from TAP-dependent and -independent pools was enhanced strongly by tapasin. Thus, tapasin acts as a chaperone and/or peptide editor that facilitates assembly of peptides with HLA class I molecules independently of mediating their interaction with TAP and/or retention in the endoplasmic reticulum.
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U2 - 10.1074/jbc.274.44.31349
DO - 10.1074/jbc.274.44.31349
M3 - Article
C2 - 10531335
AN - SCOPUS:0033615726
SN - 0021-9258
VL - 274
SP - 31349
EP - 31358
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 44
ER -