Wylie J L, Hatch G M, McClarty G
Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada.
J Bacteriol. 1997 Dec;179(23):7233-42. doi: 10.1128/jb.179.23.7233-7242.1997.
There is little information on the trafficking of eukaryotic lipids from a host cell to either the cytoplasmic membrane of or the vacuolar membrane surrounding intracellular pathogens. Purified Chlamydia trachomatis, an obligate intracellular bacterial parasite, contains several eukaryotic glycerophospholipids, yet attempts to demonstrate transfer of these lipids to the chlamydial cell membrane have not been successful. In this report, we demonstrate that eukaryotic glycerophospholipids are trafficked from the host cell to C. trachomatis. Phospholipid trafficking was assessed by monitoring the incorporation of radiolabelled isoleucine, a precursor of C. trachomatis specific branched-chain fatty acids, into host-derived glycerophospholipids and by monitoring the transfer of host phosphatidylserine to chlamydiae and its subsequent decarboxylation to form phosphatidylethanolamine. Phospholipid trafficking to chlamydiae was unaffected by brefeldin A, an inhibitor of Golgi function. Furthermore, no changes in trafficking were observed when C. trachomatis was grown in a mutant cell line with a nonfunctional, nonspecific phospholipid transfer protein. Host glycerophospholipids are modified by C. trachomatis, such that a host-synthesized straight-chain fatty acid is replaced with a chlamydia-synthesized branched-chain fatty acid. We also demonstrate that despite the acquisition of host-derived phospholipids, C. trachomatis is capable of de novo synthesis of phospholipids typically synthesized by prokaryotic cells. Our results provide novel information on chlamydial phospholipid metabolism and eukaryotic cell lipid trafficking, and they increase our understanding of the evolutionary steps leading to the establishment of an intimate metabolic association between an obligate intracellular bacterial parasite and a eukaryotic host cell.
关于真核生物脂质从宿主细胞转运至细胞内病原体周围的细胞质膜或液泡膜的信息很少。纯化的沙眼衣原体是一种专性细胞内寄生细菌，含有几种真核甘油磷脂，但试图证明这些脂质向沙眼衣原体细胞膜的转移尚未成功。在本报告中，我们证明真核甘油磷脂从宿主细胞转运至沙眼衣原体。通过监测放射性标记的异亮氨酸（沙眼衣原体特异性支链脂肪酸的前体）掺入宿主衍生的甘油磷脂中，以及监测宿主磷脂酰丝氨酸向衣原体的转移及其随后脱羧形成磷脂酰乙醇胺来评估磷脂转运。向衣原体的磷脂转运不受高尔基体功能抑制剂布雷菲德菌素A的影响。此外，当沙眼衣原体在具有无功能的非特异性磷脂转移蛋白的突变细胞系中生长时，未观察到转运变化。宿主甘油磷脂被沙眼衣原体修饰，使得宿主合成的直链脂肪酸被衣原体合成的支链脂肪酸取代。我们还证明，尽管获得了宿主衍生的磷脂，沙眼衣原体仍能够从头合成通常由原核细胞合成的磷脂。我们的结果提供了关于衣原体磷脂代谢和真核细胞脂质转运的新信息，并增进了我们对导致专性细胞内寄生细菌与真核宿主细胞之间建立紧密代谢关联的进化步骤的理解。
