HLA class II histocompatibility antigen, DRB1 beta chain is a protein that in humans is encoded by the HLA-DRB1gene.[1] DRB1 encodes the most prevalent beta subunit of HLA-DR. Several alleles of DRB1 (shared epitope alleles)[2] are associated with an increased incidence of rheumatoid arthritis.
The protein encoded by this gene belongs to the HLA class II beta chain paralogues. The class II molecule is a heterodimer consisting of an alpha (DRA) and a beta chain (DRB), both anchored in the membrane. It plays a central role in the immune system by presenting peptides derived from extracellular proteins to T helper cells. Class II molecules are constitutively expressed in professional antigen presenting cells (APC: B lymphocytes, dendritic cells, macrophages),[1] and could be induced in non-professional APCs.
Gene structure and polymorphisms
The beta chain is approximately 26-28 kDa. It is encoded by 6 exons, exon one encodes the leader peptide, exons 2 and 3 encode the two extracellular domains, exon 4 encodes the transmembrane domain and exon 5 encodes the cytoplasmic tail. Within the DR molecule the beta chain contains all the polymorphisms specifying the peptide binding specificities. Hundreds of DRB1 alleles have been described and typing for these polymorphisms is routinely done for bone marrow and kidney transplantation.[1]
Gene expression
DRB1 is expressed at a level five times higher than its paralogues DRB3, DRB4 and DRB5. DRB1 is present in all individuals. Allelic variants of DRB1 are linked with either none or one of the genes DRB3, DRB4 and DRB5. There are 4 related pseudogenes: DRB2, DRB6, DRB7, DRB8 and DRB9.[1]
Prevalence of the HLA-DRB1*10:01 allele was greatly increased in people with anti-IgLON5 disease.[3]
↑Gregersen PK, Silver J, Winchester RJ (November 1987). "The shared epitope hypothesis. An approach to understanding the molecular genetics of susceptibility to rheumatoid arthritis". Arthritis and Rheumatism. 30 (11): 1205–13. doi:10.1002/art.1780301102. PMID2446635.
↑Gaig C, Graus F, Compta Y, Högl B, Bataller L, Brüggemann N, Giordana C, Heidbreder A, Kotschet K, Lewerenz J, Macher S, Martí MJ, Montojo T, Pérez-Pérez J, Puertas I, Seitz C, Simabukuro M, Téllez N, Wandinger KP, Iranzo A, Ercilla G, Sabater L, Santamaría J, Dalmau J (May 2017). "Clinical manifestations of the anti-IgLON5 disease". Neurology. 88 (18): 1736–1743. doi:10.1212/WNL.0000000000003887. PMC5409845. PMID28381508.
Further reading
Turesson C, Matteson EL (January 2006). "Genetics of rheumatoid arthritis". Mayo Clinic Proceedings. 81 (1): 94–101. doi:10.4065/81.1.94. PMID16438485.
Ahmad T, Marshall SE, Jewell D (June 2006). "Genetics of inflammatory bowel disease: the role of the HLA complex". World Journal of Gastroenterology. 12 (23): 3628–35. doi:10.3748/wjg.v12.i23.3628. PMID16773677.
Schmidt H, Williamson D, Ashley-Koch A (May 2007). "HLA-DR15 haplotype and multiple sclerosis: a HuGE review". American Journal of Epidemiology. 165 (10): 1097–109. doi:10.1093/aje/kwk118. PMID17329717.
1pyw: Human class II MHC protein HLA-DR1 bound to a designed peptide related to influenza virus hemagglutinin, FVKQNA(MAA)AL, in complex with staphylococcal enterotoxin C3 variant 3B2 (SEC3-3B2)
2fse: Crystallographic structure of a rheumatoid arthritis MHC susceptibility allele, HLA-DR1 (DRB1*0101), complexed with the immunodominant determinant of human type II collagen
2ipk: Crystal Structure of the MHC Class II Molecule HLA-DR1 in Complex with the Fluorogenic Peptide, AcPKXVKQNTLKLAT (X=3-[5-(dimethylamino)-1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl]-L-alanine) and the Superantigen, SEC3 Variant 3B2
![2ipk: Crystal Structure of the MHC Class II Molecule HLA-DR1 in Complex with the Fluorogenic Peptide, AcPKXVKQNTLKLAT (X=3-[5-(dimethylamino)-1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl]-L-alanine) and the Superantigen, SEC3 Variant 3B2](/index.php?title=Special:Upload&wpDestFile=PDB_2ipk_EBI.jpg){kind=link}
