title: Characterization of a serine proteinase mediating encystation of Acanthamoeba.
abstract: Members of the genus Acanthamoeba, amphizoic protozoan parasites, are causative agents of granulomatous amoebic encephalitis and amoebic 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 phenylmethanesulfonyl fluoride. 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 against EMSP inhibited the expression of EMSP mRNA and significantly reduced the encystation efficiency of Acanthamoeba. An EMSP-enhanced green fluorescent protein 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 colocalizing with the autophagosome. Taken together, these results indicate that EMSP plays an important role in the differentiation of Acanthamoeba by promoting autolysis.
authors.affiliation: Department of Parasitology, Kyungpook National University School of Medicine, 101 Dongin-dong, Joong-gu, Taegu 700-422, South Korea.
authors.forename: Eun-Kyung
authors.initials: EK
authors.lastname: Moon
authors.forename: Dong-Il
authors.initials: DI
authors.lastname: Chung
authors.forename: Yeon-Chul
authors.initials: YC
authors.lastname: Hong
authors.forename: Hyun-Hee
authors.initials: HH
authors.lastname: Kong
mesh_terms: D000048:Acanthamoeba / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D000562:Amebiasis / Q000469:parasitology*; D000818:Animals; D015870:Gene Expression; D006801:Humans; D021381:Protein Transport; D015800:Protozoan Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
chemical_list: D015800:Protozoan Proteins; D012697:Serine Endopeptidases