Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Researchgrid.419636.f, Bangalore, India.
Life Science Research unit, Persistent Systems Limited, Pune, India.
mBio. 2022 Jun 28;13(3):e0063022. doi: 10.1128/mbio.00630-22. Epub 2022 Apr 14.
Emerging resistance to artemisinin (ART) has become a challenge for reducing worldwide malaria mortality and morbidity. The C580Y mutation in Plasmodium falciparum Kelch13 has been identified as the major determinant for ART resistance in the background of other mutations, which include the T38I mutation in autophagy-related protein ATG18. Increased endoplasmic reticulum phosphatidylinositol-3-phosphate (ER-PI3P) vesiculation, unfolded protein response (UPR), and oxidative stress are the proteostasis mechanisms proposed to cause ART resistance. While UPR and PI3P are known to stimulate autophagy in higher organisms to clear misfolded proteins, participation of the parasite autophagy machinery in these mechanisms of ART resistance has not yet been experimentally demonstrated. Our study establishes that ART-induced ER stress leads to increased expression of P. falciparum autophagy proteins through induction of the UPR. Furthermore, the ART-resistant K13 isolate shows higher basal expression levels of autophagy proteins than those of its isogenic counterpart, and this magnifies under starvation conditions. The copresence of K13 with ATG18 and PI3P on parasite hemoglobin-trafficking vesicles demonstrate interactions between the autophagy and hemoglobin endocytosis pathways proposed to be involved in ART resistance. Analysis of K13 mutations in 2,517 field isolates, revealing an impressive >85% coassociation between K13 C580Y and ATG18 T38I, together with our experimental studies with an ART-resistant P. falciparum strain establishes that parasite autophagy underpins various mechanisms of ART resistance and is a starting point to further explore this pathway for developing antimalarials. There is an urgent need to clearly understand the mechanisms of ART resistance as it is emerging in the Greater Mekong Subregion (GMS) and other parts of the world, such as Africa. Deciphering the mechanisms of the parasite's stress response pathways of ART resistance will provide insights to identify novel drug targets for developing new antimalarial regimens.
青蒿素（ART）耐药性的出现给降低全球疟疾死亡率和发病率带来了挑战。在其他突变的背景下，疟原虫 Kelch13 中的 C580Y 突变已被确定为 ART 耐药的主要决定因素，这些突变包括自噬相关蛋白 ATG18 的 T38I 突变。内质网磷脂酰肌醇-3-磷酸（ER-PI3P）泡囊增多、未折叠蛋白反应（UPR）和氧化应激被认为是导致 ART 耐药的蛋白稳态机制。虽然 UPR 和 PI3P 已知在高等生物中刺激自噬以清除错误折叠的蛋白质，但寄生虫自噬机制在这些 ART 耐药机制中的参与尚未通过实验证明。我们的研究表明，ART 诱导的 ER 应激通过诱导 UPR 导致疟原虫自噬蛋白表达增加。此外，ART 耐药株 K13 比其同源株的自噬蛋白表达水平更高，在饥饿条件下更为显著。K13 与 ATG18 和 PI3P 共定位在寄生虫血红蛋白转运小泡上，表明自噬和血红蛋白内吞途径之间存在相互作用，这被认为与 ART 耐药有关。对 2517 个现场分离株的 K13 突变分析显示，K13 C580Y 和 ATG18 T38I 之间惊人的>85%共同关联，以及我们对 ART 耐药疟原虫株的实验研究表明，寄生虫自噬是各种 ART 耐药机制的基础，也是进一步探索该途径开发抗疟药物的起点。 由于 ART 耐药性正在大湄公河次区域（GMS）和非洲等世界其他地区出现，因此迫切需要清楚地了解其耐药机制。解析寄生虫对 ART 耐药性的应激反应途径的机制将为识别新的药物靶点以开发新的抗疟方案提供见解。
