Fortwendel Jarrod R, Juvvadi Praveen Rao, Pinchai Nadthanan, Perfect B Zachary, Alspaugh J Andrew, Perfect John R, Steinbach William J
Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA.
Antimicrob Agents Chemother. 2009 Feb;53(2):476-82. doi: 10.1128/AAC.01154-08. Epub 2008 Nov 17.
Aspergillus fumigatus must be able to properly form hyphae and maintain cell wall integrity in order to establish invasive disease. Ras proteins and calcineurin each have been implicated as having roles in these processes. Here, we further delineate the roles of calcineurin and Ras activity in cell wall biosynthesis and hyphal morphology using genetic and pharmacologic tools. Strains deleted for three genes encoding proteins of these pathways, rasA (the Ras protein), cnaA (calcineurin), or crzA (the zinc finger transcription factor downstream of calcineurin), all displayed decreased cell wall 1,3-beta-d-glucan content. Echinocandin treatment further decreased the levels of 1,3-beta-d-glucan for all strains tested yet also partially corrected the hyphal growth defect of the DeltarasA strain. The inhibition of glucan synthesis caused an increase in chitin content for wild-type, dominant-active rasA, and DeltarasA strains. However, this important compensatory response was diminished in the calcineurin pathway mutants (DeltacnaA and DeltacrzA). Taken together, our data suggest that the Ras and calcineurin pathways act in parallel to regulate cell wall formation and hyphal growth. Additionally, the calcineurin pathway elements cnaA and crzA play a major role in proper chitin and glucan incorporation into the A. fumigatus cell wall.
烟曲霉必须能够正确形成菌丝并维持细胞壁完整性，以便引发侵袭性疾病。Ras蛋白和钙调神经磷酸酶均被认为在这些过程中发挥作用。在此，我们使用遗传学和药理学工具进一步阐明钙调神经磷酸酶和Ras活性在细胞壁生物合成和菌丝形态中的作用。缺失编码这些途径蛋白的三个基因（rasA（Ras蛋白）、cnaA（钙调神经磷酸酶）或crzA（钙调神经磷酸酶下游的锌指转录因子））的菌株，其细胞壁1,3-β-D-葡聚糖含量均降低。棘白菌素处理进一步降低了所有测试菌株的1,3-β-D-葡聚糖水平，但也部分纠正了ΔrasA菌株的菌丝生长缺陷。葡聚糖合成的抑制导致野生型、显性活性rasA和ΔrasA菌株的几丁质含量增加。然而，在钙调神经磷酸酶途径突变体（ΔcnaA和ΔcrzA）中，这种重要的补偿反应减弱。综上所述，我们的数据表明，Ras和钙调神经磷酸酶途径平行发挥作用，调节细胞壁形成和菌丝生长。此外，钙调神经磷酸酶途径元件cnaA和crzA在几丁质和葡聚糖正确掺入烟曲霉细胞壁中起主要作用。
