Protistology 6 (2) 103–110 (2009)
Role of Ca2+ and cAMP in a cell signaling pathway for resting cyst formation of ciliated protozoan Colpoda cucullus
Tatsuomi Matsuoka, Asuka Kondoh, Kunihisa Sabashi, Nobuaki Nagano, Takahiko Akematsu, Akemi Kida and Ryota Iino
Institute of Biological Science, Faculty of Science, Kochi University, Kochi, Japan
Resting cyst formation (encystment) of Colpoda cucullus is caused by an increase in an external Ca2+ concentration or overpopulation of Colpoda vegetative cells. The Ca2+-mediated or overpopulation-mediated encystment was suppressed by Ca2+ channel blockers (Cd2+, La3+, Ni2+), Ca2+-chelating reagents (EGTA, BAPTA), calmodulin antagonists (W-7, trifluoperazine), Rp-cAMPS (an cAMP analog antagonist) and 2’-deoxyadenosine (a P-site inhibitor of adenylate cyclase). On the other hand, by the addition of Ca2+ ionophore A23187, IBMX (an inhibitor of phosphodiesterase), cAMP or its membrane-permeable derivative, the encystment was prominently induced even in the Ca2+-free medium. These results suggest that Colpoda encystment may be mediated by an increase in cAMP concentration through the activation of adenylate cyclase whose activity is possibly regulated by Ca2+/calmodulin.
Key words: cAMP, Ca2+/calmodulin, cyst formation, Colpoda
Address for correspondence. Tatsuomi Matsuoka.Institute of Biological Science, Faculty of Science, Kochi University, Kochi 780-8520, Japan, e-mail: email@example.com
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