Department of Life Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B5 Nagatsuta, Midori-ku, Yokohama, Kanagawa 266-8501, Japan.
Microbiology (Reading). 2010 Apr;156(Pt 4):1234-1243. doi: 10.1099/mic.0.033985-0. Epub 2009 Dec 17.
C9-methylated glucosylceramide is a fungus-specific sphingolipid. This lipid is a major membrane component in the cell and is thought to play important roles in the growth and virulence of several fungal species. To investigate the importance of the methyl branch of the long-chain base in glucosylceramides in pathogenic fungi, we identified and characterized a sphingolipid C9-methyltransferase gene (MTS1, C9-MethylTransferase for Sphingolipid 1) in the pathogenic yeast Candida albicans. The mts1 disruptant lacked (E,E)-9-methylsphinga-4,8-dienine in its glucosylceramides and contained (E)-sphing-4-enine and (E,E)-sphinga-4,8-dienine. Reintroducing the MTS1 gene into the mts1 disruptant restored the synthesis of (E,E)-9-methylsphinga-4,8-dienine in the glucosylceramides. We also created a disruptant of the HSX11 gene, encoding glucosylceramide synthase, which catalyses the final step of glucosylceramide synthesis, in C. albicans and compared this mutant with the mts1 disruptant. The C. albicans mts1 and hsx11 disruptants both had a decreased hyphal growth rate compared to the wild-type strain. The hsx11 disruptant showed increased susceptibility to SDS and fluconazole, similar to a previously reported sld1 disruptant that contained only (E)-sphing-4-enine in its glucosylceramides, suggesting that these strains have defects in their cell membrane structures. In contrast, the mts1 disruptant grew similarly to wild-type in medium containing SDS or fluconazole. These results suggest that the C9-methyl group of a long-chain base in glucosylceramides plays an important role in the hyphal elongation of C. albicans independent of lipid membrane disruption.
C9-甲基葡糖神经酰胺是一种真菌特有的神经鞘脂。这种脂质是细胞膜的主要成分，被认为在几种真菌的生长和毒力中发挥重要作用。为了研究葡糖神经酰胺中长链碱基甲基支链在致病真菌中的重要性，我们在致病性酵母白色念珠菌中鉴定并表征了一种神经鞘脂 C9-甲基转移酶基因（MTS1，C9-甲基转移酶用于神经鞘脂 1）。mts1 缺失突变体的葡糖神经酰胺中缺乏（E，E）-9-甲基鞘氨醇-4,8-二烯，而含有（E）-鞘氨醇-4-烯和（E，E）-鞘氨醇-4,8-二烯。将 MTS1 基因重新引入 mts1 缺失突变体中，恢复了葡糖神经酰胺中（E，E）-9-甲基鞘氨醇-4,8-二烯的合成。我们还创建了白色念珠菌中编码葡糖神经酰胺合酶的 HSX11 基因的缺失突变体，该酶催化葡糖神经酰胺合成的最后一步，并将该突变体与 mts1 缺失突变体进行了比较。与野生型菌株相比，白色念珠菌的 mts1 和 hsx11 缺失突变体的菌丝生长速度都降低了。hsx11 缺失突变体对 SDS 和氟康唑的敏感性增加，与先前报道的仅在其葡糖神经酰胺中含有（E）-鞘氨醇-4-烯的 sld1 缺失突变体相似，表明这些菌株的细胞膜结构存在缺陷。相比之下，mts1 缺失突变体在含有 SDS 或氟康唑的培养基中生长与野生型相似。这些结果表明，葡糖神经酰胺中长链碱基的 C9-甲基基团在白色念珠菌的菌丝伸长中发挥重要作用，而与脂质膜破坏无关。
