Recognition by TNF-α of the GPI-anchor glycan induces apoptosis of U937 cells
- 作者：Fukushima ; Keiko ; Ishiyama ; Chikako ; Yamashita ; Katsuko
- 关键词：GPI anchor ; β ; -N-acetylglucosaminyl phosphate diester ; Apoptosis ; TNF-α
- 刊名：Archives of Biochemistry and Biophysics
- 出版年：2004
- 期刊代码：116_00039861
- 类别：ch
- 出版时间：June 15, 2004
- 卷：426
- 期：2
- 页码：298-305
- 文件大小：334 K
摘要
Tumor necrosis factor-α (TNF-α) binds to TNF-α receptors (TNFR) to produce a hexameric (TNF-α)3–(TNFR)3 structure that stimulates apoptosis. We found by using ELISA that TNF-α binds to the glycosylphosphatidylinositol (GPI) anchor glycans of carcinoembryonic antigen, human placental alkaline phosphatase (hAP), and Tamm–Horsfall glycoprotein. These binding abilities were inhibited by 10−6M mannose-6-phosphate. Treatment of hAP with mild acid and phosphatase, which releases the N-acetylglucosamine (GlcNAc) β1→phosphate→6 residue from the GPI-anchor glycan of hAP, abrogated the binding of TNF-α to hAP. Thus, TNF-α binds to the GlcNAcβ1→phosphate→6Man residue in GPI-anchor glycans. To investigate whether the carbohydrate-binding ability of TNF-α is related to its physiological functions, human lymphoma U937 cells were used. TNF-α stimulates U937 cell apoptosis in a dose-dependent manner and the presence of mannose-6-phosphate inhibited this. TNF-α-dependent tyrosine phosphorylation of several proteins in U937 cells was also diminished by mannose-6-phosphate. Phosphatidylinositol-specific phospholipase C-pretreatment also inhibited this tyrosine phosphorylation. These data suggest that TNF-α stimulates U937 cell apoptosis by forming a high-affinity nanomeric (TNF-α)3–(TNFR)3–(GPI-anchored glycan)3 complex. The GPI-anchored glycoprotein involved remains to be identified.