Regulation of the Cdc42/Cdc24 GTPase module during Candida albicans hyphal growth
Regulation of the Cdc42/Cdc24 GTPase module during Candida albicans hyphal growth
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DOI：
10.1128/ec.4.3.588-603.2005
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发表时间：
2005-03-01
期刊：
影响因子：
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通讯作者：
Arkowitz, RA
中科院分区：
文献类型：
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作者：
Bassilana, M;Hopkins, J;Arkowitz, RA
Rho G蛋白Cdc 42及其交换因子Cdc 24是人类真菌病原体白色念珠菌菌丝生长所必需的。以前，我们报道过异位表达Cdc 24或Cdc 42的菌株不能形成菌丝，以响应血清。在这里，我们研究了这两种蛋白质在菌丝生长中的作用，使用定量实时PCR来测量菌丝特异性基因的诱导与延时显微镜。检查的菌丝特异性基因的表达取决于环AMP依赖性蛋白激酶A途径，最终在Efg 1和Tec 1转录因子。我们发现，菌株与降低水平的CDC 24或CDC 42转录诱导超特异性基因，但不能维持其表达的血清。此外，在血清中，这些突变体与野生型和突变体出芽细胞相比形成伸长的芽，如通过延时显微镜观察到的。使用Cdc 24融合到绿色荧光蛋白，我们还表明，Cdc 24的招聘，并坚持在芽管顶端菌丝生长过程中。总之，这些数据表明，Cdc 24/Cdc 42 GTdR模块是维持菌丝生长所必需的。此外，过表达研究表明，特定水平的Cdc 24和Cdc 42是重要的侵入性菌丝生长。响应于血清，CDC 24转录水平以Tec 1依赖性方式瞬时增加，G蛋白RH 0 3和Rho 1 GT3活化蛋白BEM 2转录水平也是如此。这些结果表明，Cdc 24和Tec 1之间的正反馈回路有助于增加活性Cdc 42在芽管的尖端，这是重要的菌丝形成。
The Rho G protein Cdc42 and its exchange factor Cdc24 are required for hyphal growth of the human fungal pathogen Candida albicans. Previously, we reported that strains ectopically expressing Cdc24 or Cdc42 are unable to form hyphae in response to serum. Here we investigated the role of these two proteins in hyphal growth, using quantitative real-time PCR to measure induction of hypha-specific genes together with time lapse microscopy. Expression of the hypha-specific genes examined depends on the cyclic AMP-dependent protein kinase A pathway culminating in the Efg1 and Tec1 transcription factors. We show that strains with reduced levels of CDC24 or CDC42 transcripts induce hypha-specific genes yet cannot maintain their expression in response to serum. Furthermore, in serum these mutants form elongated buds compared to the wild type and mutant budding cells, as observed by time lapse microscopy. Using Cdc24 fused to green fluorescent protein, we also show that Cdc24 is recruited to and persists at the germ tube tip during hyphal growth. Altogether these data demonstrate that the Cdc24/Cdc42 GTPase module is required for maintenance of hyphal growth. In addition, overexpression studies indicate that specific levels of Cdc24 and Cdc42 are important for invasive hyphal growth. In response to serum, CDC24 transcript levels increase transiently in a Tec1-dependent fashion, as do the G-protein RHO3 and the Rho1 GTPase activating protein BEM2 transcript levels. These results suggest that a positive feedback loop between Cdc24 and Tec1 contributes to an increase in active Cdc42 at the tip of the germ tube which is important for hypha formation.