Kidney Sulfatides in Mouse Models of Inherited Glycosphingolipid Disorders
Kidney Sulfatides in Mouse Models of Inherited Glycosphingolipid Disorders
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DOI：
10.1074/jbc.m110641200
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发表时间：
2002-06
期刊：
影响因子：
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通讯作者：
R. Sandhoff;Stefan T. Hepbildikler;R. Jennemann;R. Geyer;V. Gieselmann;R. Proia;H. Wiegandt;H. Gröne
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文献类型：
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作者：
R. Sandhoff;Stefan T. Hepbildikler;R. Jennemann;R. Geyer;V. Gieselmann;R. Proia;H. Wiegandt;H. Gröne
硫酸脂与神经节苷脂在结构上和生理上可能相似。肾功能不全可能与硫苷脂的变化相关，硫苷脂是该器官中主要的酸性鞘糖脂。为了阐明它们的体内代谢途径，在患有遗传性鞘糖脂疾病的小鼠中分析了这些化合物。研究中的小鼠缺乏编码β-氨基己糖苷酶α亚基（Hexa−/−）、β-氨基己糖苷酶β亚基（Hexb−/−）、β-氨基己糖苷酶α和β亚基（Hexa−/−和Hexb−/−）、GD 3合酶（GD 3S −/−）、GD 3合酶和GalNAc转移酶（GD 3S −/−和GalNAcT−/−）、GM 2激活蛋白（Gm 2a −/−）或芳基硫酸酯酶A（阿萨−/−）的基因。通过纳米电喷雾串联质谱法对硫苷I3 SO 3 − -GalCer（SM 4s）、II 3SO 3 − -LacCer（SM 3）、II 3SO 3 − -Gg 3Cer（SM 2a）和IV 3，II 3-（SO 3 −）2-Gg 4Cer（SB 1a）进行定量。对于小鼠肾脏中的体内情况，我们得出以下结论：1）单一酶（GalNAc转移酶）分别负责从SM 3和GM 3合成SM 2a和GM 2。2)与GD 1a类似，SB 1a通过SM 2a降解。3)SM 2a被β-氨基己糖苷酶S（Hex S）和Hex A水解为SM 3，但不被Hex B水解。这两种酶都由GM 2激活蛋白支持。4)芳基硫酸酯酶A是降解SB 1a所必需的。它可能是唯一的鞘脂硫酸酯酶裂解半乳糖基-3-硫酸酯键。此外，研究了人泰-萨二氏病患者的肝脏，其显示SM 2a的积累沿着GM 2储存。两种化合物的不同神经酰胺组成表明它们可能来源于不同的细胞类型。这些数据表明，在体内的神经节系列的硫苷脂遵循相同的代谢途径作为神经节苷脂的磺基转移酶和硫酸酯酶的唾液酸转移酶和唾液酸酶的替代。此外，发现一种新的中性GSL，IV 6 GlcNAc β-Gb 4Cer，仅在Hexa−/−和Hexb−/−小鼠肾脏中蓄积。由此，我们得出结论，Hex S在体内也有效地从中性GSL切割末端β1-6连接的HexNAc残基。
Sulfatides show structural, and possibly physiological similarities to gangliosides. Kidney dysfunction might be correlated with changes in sulfatides, the major acidic glycosphingolipids in this organ. To elucidate their in vivo metabolic pathway these compounds were analyzed in mice afflicted with inherited glycosphingolipid disorders. The mice under study lacked the genes encoding either β-hexosaminidase α-subunit (Hexa−/−), the β-hexosaminidase β-subunit (Hexb−/−), both β-hexosaminidase α and β-subunits (Hexa−/− and Hexb−/−), GD3 synthase (GD3S−/−), GD3 synthase and GalNAc transferase (GD3S−/− and GalNAcT−/−), GM2 activator protein (Gm2a−/−), or arylsulfatase A (ASA−/−). Quantification of the sulfatides,I3SO 3 − -GalCer (SM4s), II3SO 3 − -LacCer ( SM3 ),II3SO 3 − -Gg3Cer (SM2a), and IV3,II3-(SO 3 − )2-Gg4Cer (SB1a), was performed by nano-electrospray tandem mass spectrometry. We conclude for the in vivo situation in mouse kidneys that: 1) a single enzyme (GalNAc transferase) is responsible for the synthesis of SM2a and GM2 from SM3 and GM3, respectively. 2) In analogy to GD1a, SB1a is degraded via SM2a. 3) SM2a is hydrolyzed to SM3 by β-hexosaminidase S (Hex S) and Hex A, but not Hex B. Both enzymes are supported by GM2-activator protein. 4) Arylsulfatase A is required to degrade SB1a. It is probably the sole sphingolipid-sulfatase cleaving the galactosyl-3-sulfate bond. In addition, a human Tay-Sachs patient's liver was investigated, which showed accumulation of SM2a along with GM2 storage. The different ceramide compositions of both compounds indicated they were probably derived from different cell types. These data demonstrate that in vivo the sulfatides of the ganglio-series follow the same metabolic pathways as the gangliosides with the replacement of sulfotransferases and sulfatases by sialyltransferases and sialidases. Furthermore, a novel neutral GSL, IV6GlcNAcβ-Gb4Cer, was found to accumulate only in Hexa−/− and Hexb−/− mouse kidneys. From this we conclude that Hex S also efficiently cleaves terminal β1–6-linked HexNAc residues from neutral GSLs in vivo.