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

Biochemical Journal - Tập 314 Số 3 - Trang 969-976 - 1996
Minoru Hatanaka1,2, Tsukasa Seya2,3, Misako Matsumoto2, Tomoko Hara2, Masaru Nonaka4, Norimitsu Inoue5, Junji Takeda5, Akira Shimizu1
1Department of Clinical Pathology, Osaka Medical College, Takatsuki 569, Japan
2Department of Immunology, Center for Adult Diseases Osaka, Higashinari-ku, Osaka 537, Japan
3PRESTO, JRDC, Kyoto 619-02, Japan
4Department of Biochemistry, Nagoya City University Medical School, Mizuho-ku, Nagoya 467, Japan
5Department of Immunoregulation, Research Institute for Microbial Diseases, Suita, Osaka 565, Japan

Tóm tắt

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 nocturnal 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.

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Biochemical Journal

Tập 314 Số 3

969-976

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