Norton Tiffany S, Al Abdallah Qusai, Hill Amy M, Lovingood Rachel V, Fortwendel Jarrod R
a Department of Microbiology and Immunology , University of South Alabama , Mobile , AL , USA.
b Department of Clinical Pharmacy , University of Tennessee Health Science Center , Memphis , TN , USA.
Virulence. 2017 Oct 3;8(7):1401-1416. doi: 10.1080/21505594.2017.1328343. Epub 2017 May 10.
Post-translational prenylation mechanisms, including farnesylation and geranylgeranylation, mediate both subcellular localization and protein-protein interaction in eukaryotes. The prenyltransferase complex is an αβ heterodimer in which the essential α-subunit is common to both the farnesyltransferase and the geranylgeranyltransferase type-I enzymes. The β-subunit is unique to each enzyme. Farnesyltransferase activity is an important mediator of protein localization and subsequent signaling for multiple proteins, including Ras GTPases. Here, we examined the importance of protein farnesylation in the opportunistic fungal pathogen Aspergillus fumigatus through generation of a mutant lacking the farnesyltransferase β-subunit, ramA. Although farnesyltransferase activity was found to be non-essential in A. fumigatus, diminished hyphal outgrowth, delayed polarization kinetics, decreased conidial viability, and irregular distribution of nuclei during polarized growth were noted upon ramA deletion (ΔramA). Although predicted to be a target of the farnesyltransferase enzyme complex, we found that localization of the major A. fumigatus Ras GTPase protein, RasA, was only partially regulated by farnesyltransferase activity. Furthermore, the farnesyltransferase-deficient mutant exhibited attenuated virulence in a murine model of invasive aspergillosis, characterized by decreased tissue invasion and development of large, swollen hyphae in vivo. However, loss of ramA also led to a Cyp51A/B-independent increase in resistance to triazole antifungal drugs. Our findings indicate that protein farnesylation underpins multiple cellular processes in A. fumigatus, likely due to the large body of proteins affected by ramA deletion.
翻译后异戊二烯化机制，包括法尼基化和香叶基香叶基化，介导真核生物中的亚细胞定位和蛋白质-蛋白质相互作用。异戊二烯基转移酶复合物是一种αβ异二聚体，其中必需的α亚基是法尼基转移酶和I型香叶基香叶基转移酶共有的。β亚基对每种酶来说都是独特的。法尼基转移酶活性是多种蛋白质（包括Ras GTP酶）的蛋白质定位和后续信号传导的重要介质。在这里，我们通过生成一个缺乏法尼基转移酶β亚基ramA的突变体，研究了蛋白质法尼基化在机会性真菌病原体烟曲霉中的重要性。虽然发现法尼基转移酶活性在烟曲霉中不是必需的，但在缺失ramA（ΔramA）后，观察到菌丝生长减少、极化动力学延迟、分生孢子活力降低以及极化生长过程中细胞核分布不规则。虽然预计是法尼基转移酶复合物的一个靶点，但我们发现烟曲霉主要Ras GTP酶蛋白RasA的定位仅部分受法尼基转移酶活性调节。此外，法尼基转移酶缺陷型突变体在侵袭性曲霉病小鼠模型中表现出毒力减弱，其特征是体内组织侵袭减少和大的肿胀菌丝发育。然而，ramA的缺失也导致对三唑类抗真菌药物的抗性在不依赖Cyp51A/B的情况下增加。我们的研究结果表明，蛋白质法尼基化支撑着烟曲霉中的多个细胞过程，这可能是由于受ramA缺失影响的大量蛋白质所致。
