title: The role of tapasin in MHC class I antigen assembly.
abstract: The discovery of tapasin has shed new light on the mechanisms of major histocompatibility complex (MHC) class I assembly in the endoplasmic reticulum (ER). Tapasin appears to play an important role in the stable assembly of class I molecules with peptide, however, the precise function of tapasin remains elusive. The pursuit of tapasin function is complicated by the observation that tapasin is not required for successful antigen presentation by all class I molecules. In addition, current data suggest that the putative role of tapasin as a bridging molecule between transporter associated with antigen presentation (TAP) and class I is only of minor importance in tapasin action, and tapasin' s major role appears to be as an active cofactor in the assembly of class I. Furthermore, it is clear that class I molecules can follow multiple pathways for successful assembly in the ER. These pathways may or may not include the interaction of class I molecules with the accessory proteins tapasin, calreticulin, ERp57, or TAP. I would like to suggest that the particular pathway utilized by a given class I molecule depends more upon the availability of appropriate peptides rather than on an intrinsic property of the class I molecule, and that tapasin may serve a peptide editing function.
authors.affiliation: H. Lee Moffitt Cancer Center and Research Institute, and the Department of Biochemistry and Molecular Biology, University of South Florida College of Medicine, Tampa 33612, USA. androlma@moffitt.usf.edu
authors.forename: M J
authors.initials: MJ
authors.lastname: Androlewicz
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D017951:Antigen Presentation; D017920:Antiporters / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D037282:Calreticulin; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000502:physiology*; D007535:Isomerases / Q000378:metabolism; D026901:Membrane Transport Proteins; D010455:Peptides / Q000378:metabolism; D019704:Protein Disulfide-Isomerases; D012261:Ribonucleoproteins / Q000378:metabolism
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D017920:Antiporters; D002135:Calcium-Binding Proteins; D037282:Calreticulin; D006360:Heat-Shock Proteins; D015395:Histocompatibility Antigens Class I; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; D010455:Peptides; D012261:Ribonucleoproteins; C073119:TAP1 protein, human; C107762:tapasin; D007535:Isomerases; D019704:Protein Disulfide-Isomerases; C085868:PDIA3 protein, human