Eukaryotic Cell doi:10.1128/EC.00068-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Characterization of a serine proteinase mediating encystation of Acanthamoeba
Eun-Kyung Moon,
Dong-Il Chung,
Yeon-Chul Hong,
and
Hyun-Hee Kong*
Department of Parasitology, Kyungpook National University School of Medicine, Taegu, Korea
* To whom correspondence should be addressed. Email:
hhkong{at}mail.knu.ac.kr.
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Abstract |
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The genus Acanthamoeba, an amphizoic protozoan parasite is a causative agent of granulomatous amebic encephalitis (GAE) and amebic keratitis. Proteinases play a role in various biologic actions in Acanthamoeba including host tissue destruction, pathogenesis, and digestion of phagocytosed food. Interestingly, we found that encystation of Acanthamoeba was inhibited by the serine proteinase inhibitor, PMSF. In this study, we characterize a serine proteinase that is involved in mediating the encystation of Acanthamoeba. This encystation-mediating serine proteinase (EMSP) is shown to be highly expressed during encystation by real-time PCR and western blot analysis. Chemically synthesized small interfering RNA (siRNA) against EMSP inhibited the expression of EMSP mRNA and significantly reduced the encystation efficiency of Acanthamoeba. An EMSP-EGFP fusion protein localized to vesicle-like structures within the amoeba. Using LysoTracker analysis, these vesicular structures were confirmed to be lysosomes. After incubation of the transfected amoeba in encystment media, small fluorescent vesicle-like structures gathered and formed ball-like structures, which were identified as co-localizing with the autophagosome. Taken together, these results indicate that EMSP plays an important role in the differentiation of Acanthamoeba by promoting autolysis.
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