Leishmania spp. are protozoan parasites that cause a spectrum of important diseases in humans. These parasites develop as extracellular promastigotes in the digestive tract of their insect vectors and as obligate intracellular amastigotes that infect macrophages and other phagocytic cells in their vertebrate hosts. Promastigote-to-amastigote differentiation is associated with marked changes in metabolism, including the upregulation of enzymes involved in fatty acid β-oxidation, which may reflect adaptation to the intracellular niche. Here, we have investigated the function of one of these enzymes, a putative 2,4-dienoyl-coenzyme A (CoA) reductase (DECR), which is specifically required for the β-oxidation of polyunsaturated fatty acids. The Leishmania DECR shows close homology to bacterial DECR proteins, suggesting that it was acquired by lateral gene transfer. It is present in other trypanosomatids that have obligate intracellular stages (i.e., Trypanosoma cruzi and Angomonas) but is absent from dixenous parasites with an exclusively extracellular lifestyle (i.e., Trypanosoma brucei). A DECR-green fluorescent protein (GFP) fusion protein was localized to the mitochondrion in both promastigote and amastigote stages, and the levels of expression increased in the latter stages. A Leishmania major Δdecr null mutant was unable to catabolize unsaturated fatty acids and accumulated the intermediate 2,4-decadienoyl-CoA, confirming DECR’s role in β-oxidation. Strikingly, the L. major Δdecr mutant was unable to survive in macrophages and was avirulent in BALB/c mice. These findings suggest that β-oxidation of polyunsaturated fatty acids is essential for intracellular parasite survival and that the bacterial origin of key enzymes in this pathway could be exploited in developing new therapies.

中文翻译：

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利什曼原虫编码细菌样2,4-二烯酰辅酶A还原酶，该酶是脂肪酸β-氧化和细胞内寄生虫存活所必需的。

利什曼原虫属 是原生动物的寄生虫，可导致人类一系列重要疾病。这些寄生虫在其昆虫载体的消化道中发展为胞外前鞭毛体，并在感染脊椎动物宿主中的巨噬细胞和其他吞噬细胞时成为专性的胞内变形虫。前鞭毛体到鞭毛体的分化与代谢的显着变化有关，包括与脂肪酸β-氧化有关的酶的上调，这可能反映了对细胞内生态位的适应性。在这里，我们研究了其中一种酶的功能，即假定的2，4-二烯酰基辅酶A（CoA）还原酶（DECR），这对于多不饱和脂肪酸的β-氧化特别需要。该利什曼原虫DECR与细菌DECR蛋白具有高度同源性，表明它是通过横向基因转移获得的。它存在于其他具专性细胞内阶段的锥虫（例如锥虫锥虫和锥虫），但不存在具有纯胞外生活习惯的双体寄生虫（即锥虫锥虫）。DECR-绿色荧光蛋白（GFP）融合蛋白在前鞭毛体和鞭毛体两个阶段均定位于线粒体，在后一个阶段表达水平增加。一个硕大利什曼原虫Δ DECRnull突变体无法分解代谢不饱和脂肪酸，并积累了中间体2,4-癸二烯酰辅酶A，证实了DECR在β氧化中的作用。引人注目的是，硕大利什曼原虫Δ DECR突变体不能在巨噬细胞生存和BALB / c小鼠是无毒力的。这些发现表明，多不饱和脂肪酸的β-氧化对于细胞内寄生虫的生存至关重要，该途径中关键酶的细菌起源可用于开发新疗法。