| Tissue Specificity | Expressed in professional APCs: macrophages, dendritic cells and B cells (at protein level). Expressed in thymic epithelial cells (at protein level). |
| Post Translational Modifications | Ubiquitinated by MARCHF1 or MARCHF8 at Lys-244 leading to down-regulation of MHCII. When associated with ubiquitination of the beta chain at 'Lys-254', the down-regulation of MHCII may be highly effective. |
| Function | An alpha chain of antigen-presenting major histocompatibility complex class II (MHCII) molecule. In complex with the beta chain HLA-DRB, displays antigenic peptides on professional antigen presenting cells (APCs) for recognition by alpha-beta T cell receptor (TCR) on HLA-DR-restricted CD4-positive T cells. This guides antigen-specific T-helper effector functions, both antibody-mediated immune response and macrophage activation, to ultimately eliminate the infectious agents and transformed cells. Typically presents extracellular peptide antigens of 10 to 30 amino acids that arise from proteolysis of endocytosed antigens in lysosomes. In the tumor microenvironment, presents antigenic peptides that are primarily generated in tumor-resident APCs likely via phagocytosis of apoptotic tumor cells or macropinocytosis of secreted tumor proteins. Presents peptides derived from intracellular proteins that are trapped in autolysosomes after macroautophagy, a mechanism especially relevant for T cell selection in the thymus and central immune tolerance. The selection of the immunodominant epitopes follows two processing modes: 'bind first, cut/trim later' for pathogen-derived antigenic peptides and 'cut first, bind later' for autoantigens/self-peptides. The anchor residue at position 1 of the peptide N-terminus, usually a large hydrophobic residue, is essential for high affinity interaction with MHCII molecules. |
| Protein Name | Hla Class Ii Histocompatibility Antigen - Dr Alpha ChainMhc Class Ii Antigen Dra |
| Database Links | Reactome: R-HSA-202424Reactome: R-HSA-202427Reactome: R-HSA-202430Reactome: R-HSA-202433Reactome: R-HSA-2132295Reactome: R-HSA-389948Reactome: R-HSA-877300 |
| Cellular Localisation | Cell MembraneSingle-Pass Type I Membrane ProteinEndoplasmic Reticulum MembraneEarly Endosome MembraneLate Endosome MembraneLysosome MembraneAutolysosome MembraneThe Mhcii Complex Transits Through A Number Of Intracellular Compartments In The Endocytic Pathway Until It Reaches The Cell Membrane For Antigen PresentationComponent Of Immunological Synapses At The Interface Between T Cell And Apc |
| Alternative Protein Names | Hla Class Ii Histocompatibility Antigen - Dr Alpha Chain proteinMhc Class Ii Antigen Dra proteinHLA-DRA proteinHLA-DRA1 protein |
Information sourced from Uniprot.org
