Tani Motohiro, Toume Moeko
Department of Chemistry, Faculty of Sciences, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
Microbiology (Reading). 2015 Dec;161(12):2369-83. doi: 10.1099/mic.0.000187. Epub 2015 Sep 23.
In the yeast Saccharomyces cerevisiae, complex sphingolipids have three types of polar head group and five types of ceramide; however, the physiological significance of the structural diversity is not fully understood. Here, we report that deletion of vacuolar H+-ATPase (V-ATPase) in yeast causes dramatic alteration of the complex sphingolipid composition, which includes decreases in hydroxylation at the C-4 position of long-chain bases and the C-2 position of fatty acids in the ceramide moiety, decreases in inositol phosphorylceramide (IPC) levels, and increases in mannosylinositol phosphorylceramide (MIPC) and mannosyldiinositol phosphorylceramide [M(IP)2C] levels. V-ATPase-deleted cells exhibited slow growth at pH 7.2, whereas the increase in MIPC levels was significantly enhanced when V-ATPase-deleted cells were incubated at pH 7.2. The protein expression levels of MIPC and M(IP)2C synthases were significantly increased in V-ATPase-deleted cells incubated at pH 7.2. Loss of MIPC synthesis or an increase in the hydroxylation level of the ceramide moiety of sphingolipids on overexpression of Scs7 and Sur2 sphingolipid hydroxylases enhanced the growth defect of V-ATPase-deleted cells at pH 7.2. On the contrary, the growth rate of V-ATPase-deleted cells was moderately increased on the deletion of SCS7 and SUR2. In addition, supersensitivities to Ca2+, Zn2+ and H2O2, which are typical phenotypes of V-ATPase-deleted cells, were enhanced by the loss of MIPC synthesis. These results indicate the possibility that alteration of the complex sphingolipid composition is an adaptation mechanism for a defect of V-ATPase.
在酿酒酵母中，复杂鞘脂有三种类型的极性头部基团和五种类型的神经酰胺；然而，这种结构多样性的生理意义尚未完全了解。在此，我们报道酵母中液泡H⁺-ATP酶（V-ATP酶）的缺失会导致复杂鞘脂组成的显著改变，这包括神经酰胺部分中长链碱基C-4位和脂肪酸C-2位的羟基化减少、肌醇磷酸神经酰胺（IPC）水平降低以及甘露糖基肌醇磷酸神经酰胺（MIPC）和甘露糖基二肌醇磷酸神经酰胺[M(IP)₂C]水平升高。V-ATP酶缺失的细胞在pH 7.2时生长缓慢，而当V-ATP酶缺失的细胞在pH 7.2下培养时，MIPC水平的增加显著增强。在pH 7.2下培养的V-ATP酶缺失的细胞中，MIPC和M(IP)₂C合酶的蛋白质表达水平显著增加。在过表达Scs7和Sur2鞘脂羟化酶时，MIPC合成的缺失或鞘脂神经酰胺部分羟基化水平的增加会增强V-ATP酶缺失的细胞在pH 7.2时的生长缺陷。相反，缺失SCS7和SUR2会适度提高V-ATP酶缺失的细胞的生长速率。此外，MIPC合成的缺失会增强对Ca²⁺、Zn²⁺和H₂O₂的超敏感性，这是V-ATP酶缺失细胞的典型表型。这些结果表明复杂鞘脂组成的改变可能是对V-ATP酶缺陷的一种适应机制。
