Protein phosphatase 2C is involved in the cAMP-dependent ciliary control in Paramecium caudatum.
Forward swimming of the Triton-extracted model of Paramecium is stimulated by cAMP. Backward swimming of the model induced by Ca(2+) is depressed by cAMP. Cyclic AMP and Ca(2+) act antagonistically in setting the direction of the ciliary beat. Some ciliary axonemal proteins from Paramecium caudatum are phosphorylated in a cAMP-dependent manner. In the presence of cAMP, axonemal 29- and 65-kDa polypeptides were phosphorylated by endogenous A-kinase in vitro. These phosphoproteins, however, were not dephosphorylated after in vitro phosphorylation, presumably because of the low endogenous phosphoprotein phosphatase activity associated with isolated axonemes. We purified the protein phosphatase that specifically dephosphorylated the 29- and 65-kDa phosphoproteins from Paramecium caudatum. The molecular weight of the protein phosphatase was 33 kDa. The protein phosphatase had common characteristics as protein phosphatase 2C (PP2C). The characteristics of the protein phosphatase were the same as those of the PP2C from Paramecium tetraurelia (PtPP2C) [Grothe et al., 1998: J. Biol. Chem. 273:19167-19172]. We concluded that the phosphoprotein phosphatase is the PP2C from Paramecium caudatum (PcPP2C). The PcPP2C markedly accelerated the backward swimming of the Triton-extracted model in the presence of Ca(2+). On the other hand, the PcPP2C slightly depressed the forward swimming speed. This indicates that the PP2C plays a role in the cAMP-dependent regulation of ciliary movement in Paramecium caudatum through dephosphorylation of 29- and/or 65-kDa regulatory phosphoproteins by terminating the action of cAMP.
Noguchi
Munenori
M
Department of Environmental Biology and Chemistry, Faculty of Science, Toyama University, Toyama, Japan.noguchi@sci.toyama-u.ac.jp
Sasaki
Jun-Ya
JY
Kamachi
Hiroyuki
H
Inoue
Hiroshi
H
D000814:Aniline Compounds; D000818:Animals; D002923:Cilia / Q000201:enzymology*; D000242:Cyclic AMP / Q000378:metabolism*; D003902:Detergents; D007202:Indicators and Reagents; D009596:Nitrophenols; D017830:Octoxynol; D009943:Organophosphorus Compounds; D010247:Paramecium / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D000071636:Protein Phosphatase 2C; D013347:Subcellular Fractions / Q000201:enzymology; D013550:Swimming
D000814:Aniline Compounds; D003902:Detergents; D007202:Indicators and Reagents; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D010750:Phosphoproteins; C008644:nitrophenylphosphate; C068798:4-aminophenylphosphate; D017830:Octoxynol; D000242:Cyclic AMP; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C