Urban Constantin, Xiong Xin, Sohn Kai, Schröppel Klaus, Brunner Herwig, Rupp Steffen
Fraunhofer IGB, 70569 Stuttgart, Germany.
Mol Microbiol. 2005 Sep;57(5):1318-41. doi: 10.1111/j.1365-2958.2005.04771.x.
Candida albicans is one of the most common fungal pathogens in humans. The cell wall is the first contact site between host and pathogen and thus is critical for colonization and infection of the host. We have identified Tsa1p, a protein that is differentially localized to the cell wall of C. albicans in hyphal cells but remains in the cytosol and nucleus in yeast-form cells. This is different from Saccharomyces cerevisiae, where the homologous protein solely has been found in the cytoplasm. We report here that TSA1 confers resistance towards oxidative stress as well as is involved in the correct composition of hyphal cell walls. However, no significant change of the cell wall composition was observed in a TSA1 deletion strain in yeast-form cells, which is in good agreement with the observation that Tsa1p is absent from the yeast-form cell wall. This indicates that Tsa1p of C. albicans might represent a moonlighting protein with specific functions correlating to its respective localization. Furthermore, the translocation of Tsa1p to the hyphal cell wall of C. albicans depends on Efg1p, suggesting a contribution of the cAMP/PKA pathway to the localization of this protein. In a strain deleted for TUP1 that filaments constitutively Tsa1p can be found in the cell wall under all conditions tested, confirming the result that Tsa1p localization to the cell wall is correlated to the morphology of C. albicans.
白色念珠菌是人类最常见的真菌病原体之一。细胞壁是宿主与病原体的首个接触位点，因此对于宿主的定殖和感染至关重要。我们鉴定出了Tsa1p，一种在菌丝细胞中差异定位于白色念珠菌细胞壁，但在酵母形态细胞中保留在细胞质和细胞核中的蛋白质。这与酿酒酵母不同，在酿酒酵母中，同源蛋白仅在细胞质中被发现。我们在此报告，TSA1赋予对氧化应激的抗性，并参与菌丝细胞壁的正确组成。然而，在酵母形态细胞的TSA1缺失菌株中未观察到细胞壁组成的显著变化，这与酵母形态细胞壁中不存在Tsa1p的观察结果高度一致。这表明白色念珠菌的Tsa1p可能代表一种兼职蛋白，其特定功能与其各自的定位相关。此外，Tsa1p向白色念珠菌菌丝细胞壁的易位依赖于Efg1p，表明cAMP/PKA途径对该蛋白的定位有贡献。在组成型产丝的TUP1缺失菌株中，在所有测试条件下均可在细胞壁中发现Tsa1p，证实了Tsa1p定位于细胞壁与白色念珠菌形态相关的结果。
