Faculty of Science, Yamaguchi University, Yamaguchi, 753-8512, Japan.
Institute of Neuroscience, Tokushima Bunri University, Kagawa, 769-2193, Japan.
J Eukaryot Microbiol. 2020 Sep;67(5):532-540. doi: 10.1111/jeu.12800. Epub 2020 May 24.
Paramecium shows rapid forward swimming due to increased beat frequency of cilia in normal (forward swimming) direction in response to various kinds of stimuli applied to the cell surface that cause K -outflow accompanied by a membrane hyperpolarization. Some adenylate cyclases are known to be functional K channels in the membrane. Using gene-specific knockdown methods, we examined nine paralogues of adenylate cyclases in P. tetraurelia to ascertain whether and how they are involved in the mechanical stimulus-induced hyperpolarization-coupled acceleration of forward swimming. Results demonstrated that knockdown of the adenylate cyclase 1 (ac1)-gene and 2 (ac2)-gene inhibited the acceleration of forward swimming in response to mechanical stimulation of the cell, whereas that spared the acceleration response to external application of 8-Br-cAMP and dilution of extracellular [K ] induced hyperpolarization. Electrophysiological examination of the knockdown cells revealed that the hyperpolarization-activated inward K current is smaller than that of a normal cell. Our results suggest that AC1 and AC2 are involved in the mechanical stimulus-induced acceleration of ciliary beat in Paramecium.
草履虫因受到刺激而引起 K+外流并导致膜超极化，从而使纤毛快速向前摆动，其摆动频率增加。已知某些腺苷酸环化酶是膜上功能性的 K+通道。我们使用基因特异性敲低方法，研究了 P. tetraurelia 中的 9 种腺苷酸环化酶的同源物，以确定它们是否以及如何参与机械刺激诱导的超极化偶联的向前游动加速。结果表明，腺嘌呤核苷酸环化酶 1（ac1）-基因和 2（ac2）-基因的敲低抑制了细胞机械刺激引起的向前游动的加速，而对 8-Br-cAMP 的外部应用和细胞外 [K+]稀释引起的超极化所诱导的加速反应无影响。对敲低细胞的电生理检查表明，超极化激活内向 K+电流小于正常细胞。我们的研究结果表明，AC1 和 AC2 参与了机械刺激诱导的草履虫纤毛摆动的加速。
