Identification of an alternate splice form of tapasin in human melanoma.
Assembly of major histocompatibility complex (MHC) class I molecules with peptide in the endoplasmic reticulum requires the assistance of tapasin. Alternative splicing, which is known to regulate many genes, has been reported for tapasin only in the context of mutations. Here, we report on an alternate splice form of tapasin (tpsnΔEx3) derived from a human melanoma cell line that does not appear to be caused by mutations. Excision of exon 3 results in deletion of amino acids 70 to 156 within the beta barrel region, but the membrane proximal Ig domain, the transmembrane domain, and cytoplasmic tail of tapasin are intact. Introduction of tpsnΔEx3 into a tapasin-deficient cell line does not restore MHC class I expression at the cell surface. Similar to a previously described tapasin mutant (tpsnΔN50), tpsnΔEx3 interacts with TAP. Therefore, we used these altered forms of tapasin to test the importance of MHC class I interaction with TAP. In the presence of wild-type tapasin, transfection of tpsnΔN50, but not tpsnΔEx3, reduced MHC class I expression at the cell surface likely due its ability to compete MHC class I molecules from TAP. Together these findings suggest that tumor cells may contain alternate splice forms of tapasin which may regulate MHC class I antigen presentation.
Belicha-Villanueva
Alan
A
Department of Immunology, Roswell Park Cancer Institute, Buffalo, New York, USA.
Golding
Michelle
M
McEvoy
Sarah
S
Sarvaiya
Nilofar
N
Cresswell
Peter
P
Gollnick
Sandra O
SO
Bangia
Naveen
N
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000276:immunology / Q000378:metabolism; D017398:Alternative Splicing / Q000276:immunology*; D017951:Antigen Presentation; D045744:Cell Line, Tumor; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000378:metabolism; D006801:Humans; D008545:Melanoma / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology*; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D017384:Sequence Deletion / Q000235:genetics; D019076:Transgenes / Q000235:genetics
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D015395:Histocompatibility Antigens Class I; D026901:Membrane Transport Proteins; D046912:Multiprotein Complexes; D020033:Protein Isoforms; C073119:TAP1 protein, human; C107762:tapasin