Names & Taxonomy

Uniprot ID:
P01906
Entry Name:
DQA2_HUMAN
Status:
reviewed
Protein Names:
HLA class II histocompatibility antigen, DQ alpha 2 chain (DX alpha chain) (HLA class II histocompatibility antigen, DQ(6) alpha chain) (HLA-DQA1) (MHC class II DQA2)
Gene Names:
HLA-DQA2 HLA-DXA
Gene Names Primary:
HLA-DQA2
Organism:
Homo sapiens (Human)

Structure

Length:
255
Sequence:
MILNKALLLGALALTAVMSPCGGEDIVADHVASYGVNFYQSHGPSGQYTHEFDGDEEFYVDLETKETVWQLPMFSKFISFDPQSALRNMAVGKHTLEFMMRQSNSTAATNEVPEVTVFSKFPVTLGQPNTLICLVDNIFPPVVNITWLSNGHSVTEGVSETSFLSKSDHSFFKISYLTFLPSADEIYDCKVEHWGLDEPLLKHWEPEIPAPMSELTETLVCALGLSVGLMGIVVGTVFIIQGLRSVGASRHQGLL
Proteomes:
UP000005640

Subcellular location

Subcellular Location:
Cell membrane

Function

Function:
Binds peptides derived from antigens that access the endocytic route of antigen presenting cells (APC) and presents them on the cell surface for recognition by the CD4 T-cells. The peptide binding cleft accommodates peptides of 10-30 residues. The peptides presented by MHC class II molecules are generated mostly by degradation of proteins that access the endocytic route, where they are processed by lysosomal proteases and other hydrolases. Exogenous antigens that have been endocytosed by the APC are thus readily available for presentation via MHC II molecules, and for this reason this antigen presentation pathway is usually referred to as exogenous. As membrane proteins on their way to degradation in lysosomes as part of their normal turn-over are also contained in the endosomal/lysosomal compartments, exogenous antigens must compete with those derived from endogenous components. Autophagy is also a source of endogenous peptides, autophagosomes constitutively fuse with MHC class II loading compartments. In addition to APCs, other cells of the gastrointestinal tract, such as epithelial cells, express MHC class II molecules and CD74 and act as APCs, which is an unusual trait of the GI tract. To produce a MHC class II molecule that presents an antigen, three MHC class II molecules (heterodimers of an alpha and a beta chain) associate with a CD74 trimer in the ER to form a heterononamer. Soon after the entry of this complex into the endosomal/lysosomal system where antigen processing occurs, CD74 undergoes a sequential degradation by various proteases, including CTSS and CTSL, leaving a small fragment termed CLIP (class-II-associated invariant chain peptide). The removal of CLIP is facilitated by HLA-DM via direct binding to the alpha-beta-CLIP complex so that CLIP is released. HLA-DM stabilizes MHC class II molecules until primary high affinity antigenic peptides are bound. The MHC II molecule bound to a peptide is then transported to the cell membrane surface. In B-cells, the interaction between HLA-DM and MHC class II molecules is regulated by HLA-DO. Primary dendritic cells (DCs) also to express HLA-DO. Lysosomal microenvironment has been implicated in the regulation of antigen loading into MHC II molecules, increased acidification produces increased proteolysis and efficient peptide loading.
Gene Ontology Go:
clathrin-coated endocytic vesicle membrane
endocytic vesicle membrane
endosome membrane
ER to Golgi transport vesicle membrane
Golgi membrane
integral component of lumenal side of endoplasmic reticulum membrane
integral component of plasma membrane
lysosomal membrane
MHC class II protein complex
plasma membrane
trans-Golgi network membrane
transport vesicle membrane
MHC class II receptor activity
antigen processing and presentation of exogenous peptide antigen via MHC class II
cytokine-mediated signaling pathway
immune response
interferon-gamma-mediated signaling pathway
T cell costimulation
T cell receptor signaling pathway
Gene Ontology Biological Process:
antigen processing and presentation of exogenous peptide antigen via MHC class II
cytokine-mediated signaling pathway
immune response
interferon-gamma-mediated signaling pathway
T cell costimulation
T cell receptor signaling pathway
Gene Ontology Molecular Function:
MHC class II receptor activity
Gene Ontology Cellular Component:
clathrin-coated endocytic vesicle membrane
endocytic vesicle membrane
endosome membrane
ER to Golgi transport vesicle membrane
Golgi membrane
integral component of lumenal side of endoplasmic reticulum membrane
integral component of plasma membrane
lysosomal membrane
MHC class II protein complex
plasma membrane
trans-Golgi network membrane
transport vesicle membrane
Keywords:
Cell membrane
Complete proteome
Disulfide bond
Endoplasmic reticulum
Endosome
Glycoprotein
Golgi apparatus
Immunity
Lysosome
MHC II
Membrane
Polymorphism
Reference proteome
Signal
Transmembrane
Transmembrane helix

Publication

PubMed ID:
3036828 6584734 3610256 14574404 8026991 2513578 9036956 8598037 11684289 18046453 17241953 19092054 19533806 22407913