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白念珠菌是一种条件致病真菌,在健康人体口腔或胃肠道中以无害共生菌的形式存在。在免疫功能低下的患者中,能够导致危及生命的全身性感染。近年来,随着癌症患者、器官移植接受者等免疫功能低下人群不断增加,白念珠菌感染引发的严重疾病的发病率不断攀升[1-2],死亡率粗略估计已高于40%[3]。
高适应性是白念珠菌传播和致病的关键因素之一,包括对宿主和外界环境的适应性、形态的转换以及对抗真菌药物的适应性。代谢的改变能够影响白念珠菌的药物敏感性,Ene等[4]发现培养基中碳源由葡萄糖转变为乳酸后白念珠菌对抗真菌药物(咪康唑、两性霉素B、卡泊芬净)的敏感性发生改变。线粒体作为重要的代谢细胞器, 其中的某些基因缺失或者功能缺陷,会导致白念珠菌药物敏感性的变化,Sun等[5]发现线粒体复合体I相关基因GOA1和NDH51的缺失会导致白念珠菌对唑类药物敏感性上升,Edwina等[6]的研究发现线粒体关键基因FZO1的缺失能够增强白念珠菌对唑类药物的敏感性。
本课题组前期发现SDH2基因缺失导致白念珠菌致病力显著下降,并发现白念珠菌无法利用非发酵碳源[7]。生物信息学分析显示SDH2基因编码琥珀酸脱氢酶(SDH)的铁硫亚基,琥珀酸脱氢酶在三羧酸循环和线粒体电子传递链中均发挥作用,是能量代谢中重要的一环。SDH2基因可能在白念珠菌代谢过程中发挥重要的作用,那么它是否能够通过影响代谢从而改变白念珠菌的环境适应性呢?本研究聚焦SDH2基因对白念珠菌环境适应性的影响,包括对外界压力应答和药物敏感性的影响,并探索其可能的机制。
The role of SDH2 gene in the environmental adaptability of Candida albicans
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摘要:
目的 探究SDH2基因在白念珠菌环境适应性中的作用。 方法 以野生型白念珠菌SC5314、SDH2基因敲除菌sdh2 Δ/Δ 、基因回复菌sdh2 Δ /SDH2为实验对象;应用点板实验考察野生型菌、SDH2缺失菌和回复菌对外界压力刺激剂和抗真菌药物的敏感性;采用罗丹明6G外排实验考察SDH2基因缺失对白念珠菌药物外排能力的影响。 结果 SDH2基因缺失后白念珠菌对细胞壁应激刺激剂咖啡因、氧化应激刺激剂二酰胺和甲萘醌表现出轻微耐受,值得注意的是SDH2基因敲除菌sdh2 Δ/Δ 对唑类抗真菌药物的敏感性明显增高,SDH2缺失导致白念珠菌药物外排能力下降。 结论 SDH2缺失会导致白念珠菌对环境适应性的改变,包括对外界环境压力应答的改变和对唑类抗真菌药物敏感性的增加,以SDH2为靶基因,开发真菌特异性SDH2抑制剂,有望发现与唑类药物协同的新型抗真菌药物。 Abstract:Objective To investigate the role of SDH2 gene in the environmental adaptability of Candida albicans. Methods Wild-type C. albicans strain SC5314, SDH2 gene knockout mutant sdh2 Δ/Δ and reintegrated strain sdh2 Δ /SDH2 were used as experimental objects. Spot assay was conducted to assess the sensitivity of the WT C. albicans strain SC5314, SDH2 gene knockout mutant sdh2 Δ/Δ and reintegrated strain sdh2 Δ /SDH2 to external stress stimulants and antifungal drugs. The effect of SDH2 gene deletion on drug efflux ability of C. albicans was determined by rhodamine 6G efflux assay. Results After SDH2 gene deletion, C. albicans showed slight tolerance to cell wall stress stimulants caffeine, oxidative stress stimulators diamide and menadione. Notably, the sensitivity of SDH2 gene knockout mutant sdh2 Δ/Δ to azole antifungal drugs was significantly increased. The drug efflux capacity of C. albicans was decreased due to the deletion of SDH2 gene. Conclusion SDH2 gene deletion lead to changes in environmental adaptability of C. albicans, including changes in response to external environmental stress and increased sensitivity to azole antifungal drugs. The development of fungal-specific inhibitor targeting SDH2 gene may lead to the discovery of new antifungal drugs which have synergistic effect with azole drugs. -
Key words:
- Candida albicans /
- SDH2 /
- environmental adaptability /
- stress response /
- drug sensitivity
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