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【medical-news】寄生虫和弓形虫在宿主细胞内的生
Protein Helps Parasite, Toxoplasma Gondii, Survive in Host Cells
ScienceDaily (Dec. 28, 2010) — Researchers at Washington University School of Medicine in St. Louis have learned why changes in a single gene, ROP18, contribute substantially to dangerous forms of the parasite Toxoplasma gondii. The answer has likely moved science a step closer to new ways to beat Toxoplasma and many other parasites.
In a study published in Cell Host & Microbe, scientists show that the ROP18 protein disables host cell proteins that would otherwise pop a protective bubble the parasite makes for itself. The parasite puts the bubble on like a spacesuit by forming a membrane around itself when it enters host cells. This protects it from the hostile environment inside the cell, which would otherwise kill it.
"If we can find therapies that block ROP18 and other parasite proteins like it, that could give the host the upper hand in the battle against infection," says first author Sarah Fentress, a graduate student in the laboratory of L. David Sibley, PhD, professor of molecular microbiology.
Infection with Toxoplasma, or toxoplasmosis, is most familiar to the general public from the recommendation that pregnant women avoid changing cat litter. Cats are commonly infected with the parasite, as are some livestock and wildlife.
"The exact role of ROP18 and related proteins in human disease remains to be studied," says Sibley. "But mice are natural hosts of Toxoplasma, so studies in laboratory mice are relevant to the spread of infection."
Epidemiologists estimate that as many as one in every four humans is infected with Toxoplasma. Infections typically cause serious disease only in patients with weakened immune systems. In some rare cases, though, infection in patients with healthy immune systems leads to serious eye or central nervous system disease, or congenital defects or death in the fetuses of pregnant women.
In the new study, Fentress showed that the ROP18 protein binds to a class of host proteins known as immunity-related GTPases. Tests in cell cultures and animal models showed that this binding leads to a reaction that disables the GTPases, which normally would rupture the parasite's protective membrane.
"With one exception, humans don't have the same family of immunity-related GTPases," Fentress notes. "But we do have a similar group of immune recognition proteins called guanylate-binding proteins, and we are currently testing to see if ROP18 deactivates these proteins in human cells in a similar manner."
The findings could be applicable to other parasites and pathogens. Toxoplasmosis belongs to a family of parasites that includes the parasite Plasmodium, which causes malaria. All surround themselves with protective membranes when they enter host cells.
"Plasmodium doesn't make ROP18, but it does secrete related proteins called FIKK," says Fentress. "It's possible they also act to thwart host defense mechanisms like GTPases and guanylate-binding proteins."
This research was supported by the National Institutes of Health and the Veteran's Administration.
Toxoplasma gondii and other related parasites surround themselves with a membrane to protect against factors in host cells that would otherwise kill them. Scientists at Washington University School of Medicine in St. Louis have identified a parasite protein that protects this membrane from host proteins that can rupture it. According to the researchers, disabling the parasite's defensive protein could help give hosts an advantage in the battle against infection. (Credit: Wandy Beatty) 《生命世界》:寄生虫的生存之道_科学探索_科技时代_新浪网2007年10月18日... 究其原因有两点:两个阶段的生命周期和不断更换的适宜宿主. 弓形虫在生命的... 那么,寄生虫是如何顺利地在成熟以后从老鼠体内转移到猫体内的呢?寄生虫会熟...tech.sina.com.cn/...1158.shtml-2007-10-18-快照-生命世界》:寄生虫的生存之道_科学探索_科技时代_新浪网" 对抗疟疾的新思路:阻断寄主细胞内寄生虫的生存 - 生化和分子生...发表时间：2009-4-16回帖数：1宾夕法尼亚大学的研究者根据寄生虫需要依靠宿主细胞蛋白质来维持生存和进行增殖的特点,提出了一种控制由寄生虫而引起疾病的新途径.这项研究本周发表于《science》杂志上,...www.helixnet.cn/bbs/viewthr... - 2010-11-19-快照-细胞内寄生虫的生存 - 生化和分子生..." 人体十大寄生虫:弓形虫会侵袭中枢神经系统_科学探索_科技时代_...2009年7月17日... 新浪科技讯 北京时间7月17日消息 据《新科学家》杂志报道,寄生虫和人之间的... 1.钩虫 钩虫 这种寄生线虫的生命开始于人体外,它通过受污染的水、水果和蔬菜...tech.sina.com.cn/...2109.shtml-2009-07-17-快照-寄生虫:弓形虫会侵袭中枢神经系统_科学探索_科技时代_..."[标签:content2]
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作者:admin@医学,生命科学 2010-12-29 23:22
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