title: HLA-B polymorphism affects interactions with multiple endoplasmic reticulum proteins.
abstract: To explore the nature of amino acid substitutions that influence association with TAP, we compared a site-directed mutant of HLA-B*0702 (Y116D) to unmutated HLA-B7 in regard to TAP interaction. We found that the mutant had stronger association with TAP, and, in addition, with tapasin and calreticulin. These data confirm the importance of position 116 for TAP association, and indicate that (1) an aspartic acid at the 116 position can facilitate the interaction, and (2) association with tapasin and calreticulin is affected along with TAP. Furthermore, we tested three natural subtypes of HLA-B15, and found that a B15 subtype with a tyrosine at position 116 (B*1510) was strongly associated not only with TAP, but also with tapasin and calreticulin. In contrast, two B15 subtypes with a serine at position 116 (B*1518 and B*1501) exhibited very little or no association with any of these proteins. Thus, very closely related HLA-B subtypes can differ in regard to interaction with the entire assembly complex. Interestingly, when their surface expression was tested by flow cytometry, the HLA-B15 subtypes with little to no detectable intracellular assembly complex association had a slightly, yet consistently, higher level of the open heavy chain form than did the B15 subtype with intracellular assembly complex association. These data suggest that the relatively low strength or short length of interaction between endoplasmic reticulum proteins and natural HLA class I molecules can decrease their surface stability.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha 68198-6805, USA.
authors.forename: H R
authors.initials: HR
authors.lastname: Turnquist
authors.forename: H J
authors.initials: HJ
authors.lastname: Thomas
authors.forename: K R
authors.initials: KR
authors.lastname: Prilliman
authors.forename: C T
authors.initials: CT
authors.lastname: Lutz
authors.forename: W H
authors.initials: WH
authors.lastname: Hildebrand
authors.forename: J C
authors.initials: JC
authors.lastname: Solheim
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000276:immunology / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017920:Antiporters / Q000276:immunology / Q000378:metabolism*; D001224:Aspartic Acid / Q000737:chemistry; D002135:Calcium-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D037282:Calreticulin; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D015793:HLA-B7 Antigen / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology; D007136:Immunoglobulins / Q000276:immunology / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D026901:Membrane Transport Proteins; D009097:Multienzyme Complexes / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D011110:Polymorphism, Genetic; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D011817:Rabbits; D012261:Ribonucleoproteins / Q000276:immunology / Q000378:metabolism*; D012694:Serine / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D000911:Antibodies, Monoclonal; D017920:Antiporters; D002135:Calcium-Binding Proteins; D037282:Calreticulin; D015793:HLA-B7 Antigen; D007074:Immunoglobulin G; D007136:Immunoglobulins; D007976:Leupeptins; D026901:Membrane Transport Proteins; D009097:Multienzyme Complexes; D011480:Protease Inhibitors; D012261:Ribonucleoproteins; C073119:TAP1 protein, human; C107762:tapasin; C063261:acetylleucyl-leucyl-norleucinal; D001224:Aspartic Acid; D014443:Tyrosine; D012694:Serine; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex