The nonclassical MHC class I molecule Qa-1 forms unstable peptide complexes.

Abstract

The MHC class Ib molecule Qa-1 is the primary ligand for mouse CD94/NKG2A inhibitory receptors expressed on NK cells, in addition to presenting Ags to a subpopulation of T cells. CD94/NKG2A receptors specifically recognize Qa-1 bound to the MHC class Ia leader sequence-derived peptide Qdm. Qdm is the dominant peptide loaded onto Qa-1 under physiological conditions and this peptide has an optimal sequence for binding to Qa-1. Peptide dissociation experiments demonstrated that Qdm dissociates from soluble or cell surface Qa-1(b) molecules with a t(1/2) of approximately 1.5 h at 37 degrees C. In comparison, complexes of an optimal peptide (SIINFEKL) bound to the MHC class Ia molecule H-2K(b) dissociated with a t(1/2) in the range from 11 to 31 h. In contrast to K(b), the stability of cell surface Qa-1(b) molecules was independent of bound peptides, and several observations suggested that empty cell surface Qa-1(b) molecules might be unusually stable. Consistent with the rapid dissociation rate of Qdm from Qa-1(b), cells become susceptible to lysis by CD94/NKG2A(+) NK cells under conditions in which new Qa-1(b)/Qdm complexes cannot be continuously generated at the cell surface. These results support the hypothesis that Qa-1 has been selected as a specialized MHC molecule that is unable to form highly stable peptide complexes. We propose that the CD94/NKG2A-Qa-1/Qdm recognition system has evolved as a rapid sensor of the integrity of the MHC class I biosynthesis and Ag presentation pathway.

7 Figures and Tables

Statistics

050100150'04'05'06'07'08'09'10'11'12'13'14'15'16'17
Citations per Year

441 Citations

Semantic Scholar estimates that this publication has 441 citations based on the available data.

See our FAQ for additional information.

Cite this paper

@article{Kambayashi2004TheNM, title={The nonclassical MHC class I molecule Qa-1 forms unstable peptide complexes.}, author={Taku Kambayashi and Jennifer R Kraft-Leavy and Joseph G Dauner and Barbara A. Sullivan and Oskar Laur and Peter Egede Jensen}, journal={Journal of immunology}, year={2004}, volume={172 3}, pages={1661-9} }