| 20190073 |
Leitsch D, Kohsler M, Marchetti-Deschmann M, Deutsch A, Allmaier G, Duchene M, Walochnik J: A major role for cysteine proteases during the early phase of Acanthamoeba castellanii encystment. Eukaryot Cell. 2010 Feb 26.
Acanthamoeba castellanii is a facultative pathogen that has a two-staged life cycle comprising the vegetatively growing trophozoite and the dormant cyst stage. Cysts are formed when the cell encounters unfavourable conditions such as environmental stress or food deprivation. Due to their rigid double-layered wall, Acanthamoeba cysts are highly resistant to anti-amoebal drugs. This is problematic as cysts can survive initially successful chemotherapeutical treatment and cause relapses of disease. We studied the Acanthamoeba encystment process applying two-dimensional gel electrophoresis (2DE) and found that most changes in the protein content occur early in the process. Truncated actin isoforms were found to abound in the encysting cell and the levels of translation elongation factor 2 (EF2) were sharply decreased, indicating that the rate of protein synthesis must be low at this stage. In the advanced stage of encystment, however, EF2 levels and the trophozoite proteome were partly restored. The protease inhibitors PMSF and E64d inhibited the onset of encystment, whereas the protein synthesis inhibitor cycloheximide was ineffective. Changes in the protein profile, similar to those of encysting cells, could be observed with trophozoite homogenates when incubated at room temperature for several hours. Interestingly, these changes could be inhibited significantly by cysteine protease inhibitors but not by inhibitors against other proteases. Taken together, we conclude that the encystment process in A. castellanii is of a bipartite nature consisting of an initial phase of autolysis and protein degradation and an advanced stage of restoration accompanied by the expression of encystment-specific genes. |
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