Plasma Membrane Localization Is Required for RasA-Mediated Polarized Morphogenesis and Virulence of Aspergillus fumigatus
Plasma Membrane Localization Is Required for RasA-Mediated Polarized Morphogenesis and Virulence of Aspergillus fumigatus
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DOI：
10.1128/ec.00091-12
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发表时间：
2012-08-01
期刊：
影响因子：
--
通讯作者：
Steinbach, William J.
中科院分区：
文献类型：
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作者：
Fortwendel, Jarrod R.;Juvvadi, Praveen R.;Steinbach, William J.
Ras是一种高度保守的GTPase蛋白，对丝状真菌的正确极化形态发生至关重要。Ras蛋白通过翻译后添加法尼基和棕榈酰残基定位到质膜和内膜是细胞提供Ras信号输出特异性的重要机制。虽然已知烟曲霉RasA蛋白是生长发育的主要调节因子，但在极化形态发生过程中RasA的膜分布以及适当定位的Ras信号在致病性霉菌毒力中的作用尚不清楚。在这里，我们证明烟曲霉RasA主要定位于活跃生长菌丝的质膜。我们发现棕榈酰化抑制剂2-溴铝酸酯的处理破坏了正常的RasA质膜结合并减少了菌丝的生长。高度保守的RasA棕榈酰基基的靶向突变也会导致RasA在质膜上的错误定位，导致严重的菌丝异常、细胞壁结构改变和小鼠侵袭性曲霉病的毒力降低。最后，我们提供的证据表明，正确的RasA定位与erfB编码的Ras棕榈酰转移酶同源物无关，但需要erfD编码的棕榈酰转移酶复合物亚基。我们的研究结果表明，质膜相关的RasA对烟曲霉的极化形态发生、细胞壁稳定性和毒力至关重要。
Ras is a highly conserved GTPase protein that is essential for proper polarized morphogenesis of filamentous fungi. Localization of Ras proteins to the plasma membrane and endomembranes through posttranslational addition of farnesyl and palmitoyl residues is an important mechanism through which cells provide specificity to Ras signal output. Although the Aspergillus fumigatus RasA protein is known to be a major regulator of growth and development, the membrane distribution of RasA during polarized morphogenesis and the role of properly localized Ras signaling in virulence of a pathogenic mold remain unknown. Here we demonstrate that Aspergillus fumigatus RasA localizes primarily to the plasma membrane of actively growing hyphae. We show that treatment with the palmitoylation inhibitor 2-bromopalmitate disrupts normal RasA plasma membrane association and decreases hyphal growth. Targeted mutations of the highly conserved RasA palmitoylation motif also mislocalized RasA from the plasma membrane and led to severe hyphal abnormalities, cell wall structural changes, and reduced virulence in murine invasive aspergillosis. Finally, we provide evidence that proper RasA localization is independent of the Ras palmitoyltransferase homolog, encoded by erfB, but requires the palmitoyltransferase complex subunit, encoded by erfD. Our results demonstrate that plasma membrane-associated RasA is critical for polarized morphogenesis, cell wall stability, and virulence in A. fumigatus.