Kapteyn J C, Hoyer L L, Hecht J E, Müller W H, Andel A, Verkleij A J, Makarow M, Van Den Ende H, Klis F M
Swammerdam Institute of Life Sciences, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam, The Netherlands.
Mol Microbiol. 2000 Feb;35(3):601-11. doi: 10.1046/j.1365-2958.2000.01729.x.
In Candida albicans wild-type cells, the beta1, 6-glucanase-extractable glycosylphosphatidylinositol (GPI)-dependent cell wall proteins (CWPs) account for about 88% of all covalently linked CWPs. Approximately 90% of these GPI-CWPs, including Als1p and Als3p, are attached via beta1,6-glucan to beta1,3-glucan. The remaining GPI-CWPs are linked through beta1,6-glucan to chitin. The beta1,6-glucanase-resistant protein fraction is small and consists of Pir-related CWPs, which are attached to beta1,3-glucan through an alkali-labile linkage. Immunogold labelling and Western analysis, using an antiserum directed against Saccharomyces cerevisiae Pir2p/Hsp150, point to the localization of at least two differentially expressed Pir2 homologues in the cell wall of C. albicans. In mnn9Delta and pmt1Delta mutant strains, which are defective in N- and O-glycosylation of proteins respectively, we observed enhanced chitin levels together with an increased coupling of GPI-CWPs through beta1,6-glucan to chitin. In these cells, the level of Pir-CWPs was slightly upregulated. A slightly increased incorporation of Pir proteins was also observed in a beta1, 6-glucan-deficient hemizygous kre6Delta mutant. Taken together, these observations show that C. albicans follows the same basic rules as S. cerevisiae in constructing a cell wall and indicate that a cell wall salvage mechanism is activated when Candida cells are confronted with cell wall weakening.
在白色念珠菌野生型细胞中，β1,6-葡聚糖酶可提取的糖基磷脂酰肌醇（GPI）依赖性细胞壁蛋白（CWP）约占所有共价连接的CWP的88%。这些GPI-CWP中约90%，包括Als1p和Als3p，通过β1,6-葡聚糖与β1,3-葡聚糖相连。其余的GPI-CWP通过β1,6-葡聚糖与几丁质相连。β1,6-葡聚糖酶抗性蛋白部分较小，由与Pir相关的CWP组成，它们通过碱不稳定连接与β1,3-葡聚糖相连。使用针对酿酒酵母Pir2p/Hsp150的抗血清进行免疫金标记和蛋白质印迹分析表明，在白色念珠菌细胞壁中至少有两种差异表达的Pir2同源物定位。在分别在蛋白质N-糖基化和O-糖基化方面有缺陷的mnn9Δ和pmt1Δ突变菌株中，我们观察到几丁质水平升高，同时GPI-CWP通过β1,6-葡聚糖与几丁质的偶联增加。在这些细胞中，Pir-CWP的水平略有上调。在β1,6-葡聚糖缺陷的半合子kre6Δ突变体中也观察到Pir蛋白的掺入略有增加。综上所述，这些观察结果表明，白色念珠菌在构建细胞壁时遵循与酿酒酵母相同的基本规则，并表明当念珠菌细胞面临细胞壁弱化时，细胞壁挽救机制被激活。
