Mechanisms by which the surface expression of the glycosyl-phosphatidylinositol-anchored complement regulatory proteins decay-accelerating factor (CD55) and CD59 is lost in human leukaemia cell lines.
We have investigated the mechanisms of defects in the glycosyl-phosphatidylinositol (GPI)-anchored complement regulatory proteins delay-accelerating factor (DAF) and/or CD59 in a panel of human leukaemia cell lines that lack surface expression of these proteins: U937 (DAF+/CD59-), CEM (DAF-/CD59+), TALL (DAF-/CD59-) and a substrain of Ramos [Ramos(-)] (DAF-/CD59-). Northern blotting and reverse transcription-PCR revealed that the main cause of the DAF and/or CD59 deficiency is the failure of mRNA expression in most of the cell lines, except in Ramos(-) in which sufficient mRNA for DAF and CD59 was produced. U937, CEM and TALL cells were not defective in GPI anchor formation as assessed by the detection of other GPI-anchored proteins. No gene abnormality corresponding to DAF or CD59 was detected by Southern blotting. Thus the cause of the defects of DAF and/or CD59 in these leukaemia cell lines except for Ramos(-) is virtually undetectable steady-state levels of the relevant mRNA, most likely attributable to lack of transcription in these cell lines. On the other hand, Ramos(-) cells failed to generate a GPI anchor, whereas they normally expressed DAF and CD59 transcripts. The transfection of phosphatidylinositol-glycan class A (PIG-A) cDNA into Ramos(-) cells restored DAF and CD59 expression, indicating that the defective mechanism in GPI anchor formation is similar to that in paroxysmal noctural haemoglobinuria (PNH) cells, i.e. a deficiency of the PIG-A gene product. Thus the mechanisms of the defects of DAF and/or CD59 in human leukaemia cell lines are not uniform, and in most cases are different from that proposed to cause PNH.
Hatanaka
M
M
Department of Clinical Pathology, Osaka Medical College, Japan.
Seya
T
T
Matsumoto
M
M
Hara
T
T
Nonaka
M
M
Inoue
N
N
Takeda
J
J
Shimizu
A
A
D015703:Antigens, CD / Q000096:biosynthesis* / Q000235:genetics; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D018958:CD55 Antigens / Q000096:biosynthesis* / Q000235:genetics; D018957:CD59 Antigens / Q000096:biosynthesis* / Q000235:genetics; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D017931:DNA Primers; D015870:Gene Expression; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006457:Hemoglobinuria, Paroxysmal / Q000235:genetics; D006801:Humans; D007938:Leukemia; D008565:Membrane Proteins / Q000096:biosynthesis; D008969:Molecular Sequence Data; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010727:Phosphoric Diester Hydrolases / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis; D018800:Thy-1 Antigens / Q000096:biosynthesis; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases
D015703:Antigens, CD; D018958:CD55 Antigens; D018957:CD59 Antigens; D017931:DNA Primers; D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D018800:Thy-1 Antigens; C080086:phosphatidylinositol glycan-class A protein; D010727:Phosphoric Diester Hydrolases; D010738:Type C Phospholipases; D043265:Phosphatidylinositol Diacylglycerol-Lyase