Identification of Differentially Expressed Water-insoluble Proteins in the Encystment Process of Colpoda cucullus by Two-dimensional Electrophoresis and LC-MS/MS Analysis

In the encystment process of the ciliate protist Colpoda cucullus, we observed that the cell total protein abundance was reduced at 12h-1d after the onset of encystment induction subsequent to the reduction in mRNA abundance. We analyzed the alteration of the expression levels of water-insoluble proteins by two-dimensional polyacrylamide gel electrophoresis using polyoxyethylene (20) sorbitan monooleate (Tween-80), and we identified proteins whose expression levels were altered in the encystment process by a liquid chromatography tandem mass spectrometry analysis. The expression level of a 60-kDa protein (p60; heat shock protein 60) was temporarily enhanced and that of a 55-kDa protein (p55; actin) and a 49-kDa protein (p49; actin) was enhanced in the Colpoda encystment process. In mature cysts, the expression level of p55 and p49 tended to be reduced, whereas the expression level of a 50-kDa protein (p50d; -tubulin), a 25-kDa protein (p25; -tubulin) and a 52-kDa protein (p52c; -tubulin) was enhanced.