Osamu Kawase, Yoshifumi Nishikawa, Hiroshi Bannai, Houshuang Zhang, Guohong Zhang, Shigeki Jin, Eung-Goo Lee, Xuenan Xuan
PROTEOMICS 7 (20) 3718 - 3725 1615-9853 2007/10
[Refereed][Not invited] Toxoplasma gondii is an intracellular protozoan parasite that invades a wide range of nucleated cells. In the course of intracellular parasitism, the parasite releases a large variety of proteins from three secretory organelles, namely, micronemes, rhoptries and dense granules. Elevation of intracellular Ca (2+) in the parasite causes microneme discharge, and microneme, secretion is essential for the invasion. In this study, we performed a proteomic analysis of the Ca2+-dependent secretion to evaluate the protein repertoire. We found that Ca2+-mobilising agents, such as thapsigargin, NH4Cl, ethanol and a Ca2+ ionophore, A23187, promoted the secretion of the parasite proteins. The proteins, artificially secreted by A23187, were used in a comparative proteomic analysis by 2-DE followed by PMF analysis and/or N-terminal sequencing. Major known microneme proteins (MICs), such as MIC2, MIC4, MIC6 and MIC10 and apical membrane antigen 1 (AMA1), were identified, indicating that the proteomic analysis worked accurately. Interestingly, new members of secretory proteins, namely rhoptry protein 9 (ROP9) and Toxoplasma SPATR (TgSPATR), which was a homologue of a Plasmodium secreted protein with an altered thrombospondin repeat (SPATR), were detected in Ca2+-dependent secretion. Thus, we succeeded in detecting Ca2+-dependent secretory proteins in T.gondii,which contained novel. secretory proteins.