Nakaoka Y, Ooi H
J Cell Sci. 1985 Aug;77:185-95. doi: 10.1242/jcs.77.1.185.
A Triton-extracted model of Paramecium swims forwards when the Ca2+ concentration in the reactivation medium containing ATP is below 10(-6) M and swims backwards when Ca2+ concentration is above 10(-6) M. We found that cAMP (adenosine 3':5'-cyclic monophosphoric acid) inhibited Ca-induced backward swimming of the model and caused forward swimming even when the [Ca2+] was above 10(-6) M. This effect of cAMP was abolished by an inhibitor of cAMP-dependent protein kinase. In order to study the possible role of phosphorylation in the regulation of ciliary orientation, ATP in the reactivation medium was replaced by an ATP analogue, ARP gamma S (adenosine 5'-O-3-thiotriphosphate), which irreversibly thiophosphorylates proteins. In ATP gamma S medium, the model ceased both swimming and ciliary beating, but the orientation of cilia was dependent on [Ca2+]. At low [Ca2+], cilia were perpendicular to the cell surface and, with increase in [Ca2+], their orientation gradually changed towards the cell anterior. Such a change in ciliary orientation corresponds roughly to the change in the swimming direction observed in ATP medium. The ciliary orientation towards the anterior of the cell in ATP gamma S medium at high [Ca2+] was maintained when [Ca2+] was decreased. In contrast, in ATP medium, the swimming direction was reversibly changed with changes in [Ca2+]. These results suggest that the ciliary orientation is regulated not only by Ca2+ but also by cAMP, probably via protein phosphorylation.
在用含三磷酸腺苷（ATP）的再激活介质中，当钙离子浓度低于10⁻⁶M时，经曲通（Triton）提取的草履虫模型向前游动；当钙离子浓度高于10⁻⁶M时，则向后游动。我们发现，环磷酸腺苷（cAMP）可抑制钙离子诱导的该模型向后游动，即使在钙离子浓度高于10⁻⁶M时也能使其向前游动。cAMP的这种作用可被一种依赖cAMP的蛋白激酶抑制剂消除。为了研究磷酸化在纤毛方向调节中的可能作用，将再激活介质中的ATP替换为一种ATP类似物，即5'-O-3-硫代三磷酸腺苷（ARPγS），它能不可逆地使蛋白质硫代磷酸化。在含ATPγS的介质中，该模型停止游动和纤毛摆动，但纤毛的方向依赖于钙离子浓度。在低钙离子浓度时，纤毛垂直于细胞表面，随着钙离子浓度升高，其方向逐渐朝细胞前端改变。这种纤毛方向的变化大致与在含ATP介质中观察到的游动方向变化相对应。当钙离子浓度降低时，在高钙离子浓度下含ATPγS介质中纤毛朝向细胞前端的方向得以维持。相反，在含ATP的介质中，游动方向随钙离子浓度变化而可逆地改变。这些结果表明，纤毛方向可能不仅受钙离子调节，还受cAMP调节，可能是通过蛋白质磷酸化实现的。
