Deletion of Cryptococcus neoformans AIF ortholog promotes chromosome aneuploidy and fluconazole-resistance in a metacaspase-independent manner.
Deletion of Cryptococcus neoformans AIF ortholog promotes chromosome aneuploidy and fluconazole-resistance in a metacaspase-independent manner.
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DOI：
10.1371/journal.ppat.1002364
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发表时间：
2011-11
期刊：
影响因子：
6.7
通讯作者：
Heitman J
中科院分区：
文献类型：
--
作者：
Semighini CP;Averette AF;Perfect JR;Heitman J
细胞凋亡是一种程序性细胞死亡的形式，对多细胞生物的发育和稳态至关重要。细胞凋亡样细胞死亡（ALCD）已在多种真菌中被描述，包括人类机会致病菌新型隐球菌。此外，C.已知新形式病毒可诱导宿主免疫细胞凋亡，从而增强其毒力。我们的目标是描述C.新型真菌及其与宿主机制相比的独特功能，以利用内源性真菌凋亡途径作为未来新的抗真菌策略。对凋亡途径的剖析揭示了凋亡诱导因子（Aif1）和后半胱氨酸蛋白酶（Mca1和Mca2）是C.新人类我们发现，细胞凋亡途径所需的细胞融合和孢子形成在交配过程中，表明细胞凋亡可能发生在性发育过程中。以往的研究表明，抗真菌药物可诱导真菌ALCD，C。新生儿通过获得非整倍体，特别是染色体1（Chr1）的复制来适应高浓度的抗真菌剂氟康唑（FLC）。破坏aif1，而不是metacaspases，刺激非整倍体亚群的出现与Chr1二体性耐氟康唑（FLCR）在体外和体内。aif1背景中的FLCR分离株在不存在药物的情况下是稳定的，而野生型背景中的那些分离株容易恢复到FLC敏感性。我们认为，由Aif1协调的细胞凋亡可能会从人群中消除非整倍体细胞，并且该途径中的缺陷有助于在治疗期间选择非整倍体FLCR亚群。非整倍体临床分离株与染色体二体以外的Chr1表现出减少AIF1的表达，这表明AIF1的失活可能是一种新的非整倍体耐受机制的真菌，有利于选择抗真菌药物耐药性。真菌病原体可导致危及生命的疾病，并且它们引起的感染是众所周知的难以治疗的。尽管抗真菌药物可用，但大多数抑制真菌生长，但不能持续或有效地消除病原体。此外，真菌细胞与人类细胞非常相似，因此，许多可用的抗真菌剂具有毒副作用。因此，显然需要具有更少副作用的更有效的药物。我们研究了病原真菌新生隐球菌的细胞凋亡，这是一个细胞被编程为自杀的过程。我们研究了C.在灭活了参与这一途径的三个基因后，我们观察到了有性生殖的缺陷。这种交配缺陷减少了孢子的产生，孢子被吸入并引起隐球菌病。我们还发现，一个被研究的凋亡基因aif1的缺失导致了抗真菌耐药病原体的选择（当真菌细胞不再对药物产生反应时），这使得疾病的治疗更加困难。发现特异性杀死真菌细胞而不影响患者细胞的药物具有巨大的潜力。因此，触发细胞凋亡作为一种新的治疗真菌病原体的方法值得进一步研究。
Apoptosis is a form of programmed cell death critical for development and homeostasis in multicellular organisms. Apoptosis-like cell death (ALCD) has been described in several fungi, including the opportunistic human pathogen Cryptococcus neoformans. In addition, capsular polysaccharides of C. neoformans are known to induce apoptosis in host immune cells, thereby contributing to its virulence. Our goals were to characterize the apoptotic signaling cascade in C. neoformans as well as its unique features compared to the host machinery to exploit the endogenous fungal apoptotic pathways as a novel antifungal strategy in the future. The dissection of apoptotic pathways revealed that apoptosis-inducing factor (Aif1) and metacaspases (Mca1 and Mca2) are independently required for ALCD in C. neoformans. We show that the apoptotic pathways are required for cell fusion and sporulation during mating, indicating that apoptosis may occur during sexual development. Previous studies showed that antifungal drugs induce ALCD in fungi and that C. neoformans adapts to high concentrations of the antifungal fluconazole (FLC) by acquisition of aneuploidy, especially duplication of chromosome 1 (Chr1). Disruption of aif1, but not the metacaspases, stimulates the emergence of aneuploid subpopulations with Chr1 disomy that are resistant to fluconazole (FLCR) in vitro and in vivo. FLCR isolates in the aif1 background are stable in the absence of the drug, while those in the wild-type background readily revert to FLC sensitivity. We propose that apoptosis orchestrated by Aif1 might eliminate aneuploid cells from the population and defects in this pathway contribute to the selection of aneuploid FLCR subpopulations during treatment. Aneuploid clinical isolates with disomies for chromosomes other than Chr1 exhibit reduced AIF1 expression, suggesting that inactivation of Aif1 might be a novel aneuploidy-tolerating mechanism in fungi that facilitates the selection of antifungal drug resistance. Fungal pathogens can cause life-threatening diseases, and the infections that they cause are notoriously difficult to treat. Despite the availability of antifungal drugs, most inhibit fungal growth but do not consistently or efficiently eliminate the pathogen. In addition, fungal cells are very similar to human cells, and therefore, many of the available antifungal agents have toxic side effects. Thus, more efficient drugs with less adverse effects are clearly needed. We investigated apoptosis, a process in which cells become programmed to commit suicide, in the pathogenic fungus Cryptococcus neoformans. We studied genes that regulate apoptosis in C. neoformans and, after inactivating three genes involved in this pathway, we observed defects in sexual reproduction. Such mating defects decrease the production of spores, which are inhaled and cause cryptococcal disease. We also showed that the absence of one investigated apoptotic gene, aif1, resulted in the selection of antifungal-resistant pathogens (when the fungal cells no longer respond to the drug), which makes treatment of the disease more difficult. The discovery of drugs that kill fungal cells specifically without affecting the cells of the patient being treated holds great potential. Therefore, triggering apoptosis should be further investigated as a new approach to treat fungal pathogens.
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