Biophysical effects of the natural product euplotin C on the <Emphasis Type="Italic">Paramecium</Emphasis> membrane |
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Authors: | Paola Ramoino Fernando Dini Paolo Bianchini Alberto Diaspro Graziano Guella Cesare Usai |
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Institution: | 1.Dipartimento per lo Studio del Territorio e delle sue Risorse (DIP.TE.RIS.),Università di Genova,Genoa,Italy;2.Dipartimento di Biologia,Università di Pisa,Pisa,Italy;3.Dipartimento di Fisica,Università di Genova,Genoa,Italy;4.Istituto Italiano di Tecnologia (IIT), Nanofisica,Genoa,Italy;5.Dipartimento di Fisica, Laboratorio di Chimica Bioorganica,Università di Trento,Povo,Italy;6.Istituto di Biofisica, CNR,Povo,Italy;7.Istituto di Biofisica, CNR,Genoa,Italy |
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Abstract: | The effect of euplotin C—a cytotoxic secondary metabolite produced by the protist ciliate Euplotes crassus—on the voltage-dependent Ca2+ channel activity was studied in a single-celled system by analyzing the swimming behavior of Paramecium. When the intraciliary Ca2+ concentration associated with plasma membrane depolarization increases, a reversal in the direction of ciliary beating occurs,
and consequently the swimming direction changes. The ciliary reversal duration is correlated with the amount of Ca2+ influx. The present study demonstrates that the duration of continuous ciliary reversal (CCR), triggered by high external
KCl concentrations, is longer in euplotin C-treated cells. Using selective Ca2+ channel blockers, we demonstrate that euplotin C modulates Ca2+ channels similar to the T- and L-types that occur in mammalian cells. Indeed, the increase of CCR duration significantly
decreased when flunarizine and nimodipine-verapamil blockers were employed. Membrane fluidity measurements using a fluorescent
dye, 6-lauroyl-2-dimethylaminonaphtalene (laurdan), indicated that membranes in euplotin C-treated cells are more tightly
packed and ordered than membranes in control cells. Our data suggest that euplotin C enhances backward swimming in our unicellular
model system by interacting with the ciliary Ca2+ channel functions through the reduction of cell membrane fluidity. |
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