HLA-B polymorphisms and intracellular assembly modes
Section snippets
MHC class I molecules as ligands for cytotoxic T cell (CTL) and natural killer (NK) cell receptors
Major histocompatibility complex (MHC) class I molecules are ligands for antigen receptors of CD8+ CTL (Bjorkman, 1997, Rossjohn et al., 2014) and for inhibitory receptors of natural killer (NK) cells (Parham and Moffett, 2013). In a normal healthy cell, MHC class I heavy chains and light chains (β2-microglobulin; β2m) form heterodimers that bind short peptides derived from self-proteins. In cells infected with an intracellular pathogen or in cancer cells, a subset of the cellular peptides
MHC class I assembly in the ER
The assembly of MHC class I molecules occurs within the ER of cells, and involves the assembly factors TAP (transporter associated with antigen presentation) (Mayerhofer and Tampe, 2015) and tapasin (Blum et al., 2013), that are also encoded within the MHC gene complex, that includes the MHC class I heavy chain genes. In the endogenous pathway of antigen presentation, peptides that derive from cytosolic proteolysis are transported into the ER by TAP. TAP is comprised of two subunits, TAP1 and
MHC polymorphisms and assembly variations
Human TAP and tapasin sequences have no known functional polymorphisms. Rat TAP2 and chicken TAP1 and TAP2 sequences have functional polymorphisms that are known to affect peptide transport specificity. Chicken MHC haplotypes have TAP1, TAP2 and tapasin allele variants that are optimally configured for the transport and binding of peptide sequences relevant to the encoded MHC class I (Kaufman, 2015). Further studies of such functional polymorphisms are expected to provide insights into peptide
HLA-B polymorphisms and AIDS outcomes
The extreme polymorphism of the MHC class I molecules reflects evolutionary adaptations of T and NK cell responses to pathogens, in addition to NK cell functions during reproduction (Parham and Moffett, 2013). Since different combinations of HLA-A, B and C variants are present within individuals in a population, distinct sets of pathogen-derived peptides are presented during infections, resulting in the induction of CTL responses with distinct specificities. Thus, it might be expected that HLA
Acknowledgements
This work was funded by a NIH grant AI044115 (to MR). This work was supported in part by the University of Michigan Medical School Fast Forward Protein Folding Diseases Initiative.
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