Changes in protein phosphorylation in the eye of Aplysia associated with circadian rhythm regulation by serotonin.
Serotonin (5-HT) shifts the phase of the circadian oscillator of the eye of Aplysia californica in a phase dependent manner. This indicates that 5-HT acts, either directly or through some intermediaries, on a component of the oscillator. Since our goal is to identify the components of the oscillator, we are following the pathway through which 5-HT has its effect on the rhythm. The effect of 5-HT on the rhythm has been shown to be mediated by an increase in intracellular cyclic adenosine-3',5'-monophosphate (cAMP). The most likely action of cAMP is to activate cAMP-dependent protein kinase. Therefore, we used two-dimensional polyacrylamide gel electrophoresis to investigate changes in 32P labelled phosphoproteins which occur with 5-HT and other treatments. Fourteen proteins showed increased incorporation of 32P when eyes were exposed to treatments of 5-HT from CT 06 to 12. Two proteins showed decreased incorporation. 8-bt-cAMP mimicked all but one of the increases and both decreases in incorporation produced by 5-HT. 8-bt-cAMP increased incorporation into three additional proteins and decreased incorporation into three others that were not affected by 5-HT. Incorporation into one protein was increased by 5-HT but decreased by 8-bt-cAMP. By comparison, light, which has little or no effect on the rhythm at this phase, only affected one protein. The protein increased by light was also increased by 5-HT. Tetradecanoic phorbol acetate (TPA), administered during CT 06-12, also had little effect on the rhythm at this phase. TPA increased incorporation into twenty proteins and decreased incorporation into three.(ABSTRACT TRUNCATED AT 250 WORDS)
Zwartjes
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RE
Department of Biochemical and Biophysical Sciences, University of Houston, Texas 77204-5500.
Eskin
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A
D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D001048:Aplysia; D002940:Circadian Rhythm / Q000187:drug effects*; D000242:Cyclic AMP / Q000378:metabolism; D005136:Eye Proteins / Q000378:metabolism*; D008027:Light; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D005136:Eye Proteins; D012701:Serotonin; D000841:Anisomycin; D000242:Cyclic AMP; D011494:Protein Kinases; D013755:Tetradecanoylphorbol Acetate