The blood group P1 synthase gene is identical to the Gb3/CD77 synthase gene. A clue to the solution of the P1/P2/p puzzle.
Blood group P1/P2 is a glycolipid antigen system for which the genetic mechanism has not yet been clarified. We analyzed the potential of the cloned Gb3/CD77 synthase to synthesize P1 antigen, because Gb3/CD77 and P1 share a common structure, Galalpha1,4Galbeta1,4Glc (NAc)-. L cell transfectants with Gb3/CD77 synthase cDNA expressed marginal levels of P1 on the cell surface but contained high levels of P1 in the cytoplasm. P2-type erythrocytes, which were serotyped as P2, also contained definite P1 antigen inside cells, although the amounts were lower than those of P1 cells. Only p erythrocytes lacked P1 antigen corresponding with function-losing mutations in the Gb3/CD77 synthase gene. Synthesis of P1 antigen from paragloboside in vitro was demonstrated using membrane fraction of the transfectants and a fusion enzyme with protein A. These results strongly suggested that P1 synthase is identical to Gb3/CD77 synthase and appear to propose a clue for the solution of the long-pending P1/P2/p puzzle. The P1/P2 difference might result from the difference in P1 quantity based on either different enzyme activity or the presence/absence of other enzyme modulators. Because P2 erythrocytes showed lower levels of Gb3/CD77 synthase mRNA than P1, 5'-upstream promoter regions were analyzed, resulting in the identification of two P2-specific homozygous mutations. Differences in the transcriptional regulation in erythrocytes might be a major factor determining P1/P2.
Iwamura
Koichi
K
Department of Biochemistry II, Nagoya University School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-0065, Japan.
Furukawa
Keiko
K
Uchikawa
Makoto
M
Sojka
Birgitta Nilsson
BN
Kojima
Yoshinao
Y
Wiels
Joelle
J
Shiku
Hiroshi
H
Urano
Takeshi
T
Furukawa
Koichi
K
D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D001789:Blood Group Antigens / Q000096:biosynthesis / Q000235:genetics; D002462:Cell Membrane / Q000201:enzymology; D004912:Erythrocytes / Q000276:immunology; D005347:Fibroblasts; D005455:Fluorescent Antibody Technique; D005700:Galactosyltransferases / Q000096:biosynthesis / Q000235:genetics*; D015870:Gene Expression; D005915:Globosides / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology; D007150:Immunohistochemistry; D007739:L Cells; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011993:Recombinant Fusion Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013205:Staphylococcal Protein A / Q000235:genetics; D014162:Transfection; D000519:alpha-Galactosidase / Q000378:metabolism
D000911:Antibodies, Monoclonal; D001789:Blood Group Antigens; D005915:Globosides; D007075:Immunoglobulin M; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D013205:Staphylococcal Protein A; C480041:galactopyranosyl-1-4-paragloboside; C036363:paragloboside; D005700:Galactosyltransferases; C045097:UDP-galactose-lactosylceramide alpha 1-4-galactosyltransferase; D000519:alpha-Galactosidase