Document Detail


The hunt for mechanisms of circadian timing in the eye of Aplysia.
MedLine Citation:
PMID:  1611674     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The goals of our research are to understand how circadian oscillations in the eye of Aplysia california are generated and how entraining agents regulate these oscillations. These goals require identification of the molecular components of the oscillator and entrainment pathways as well as elucidation of the biochemical processes by which these components interact with one another. Our experimental strategy entails tracing environmental information along an entrainment pathway until the last component of the pathway is reached. The isolated eye of Aplysia exhibits a circadian rhythm of optic nerve impulses. This rhythm is regulated by at least two entrainment pathways. A photic pathway entrains the rhythm to light-dark cycles and an efferent serotonergic pathway relays neural information from the CNS to the oscillator. Phase shifting by light appears to involve an increase in the levels of cGMP, depolarization, and protein synthesis. Phase shifting by serotonin appears to involve an increase in the levels of cAMP, hyperpolarization, and protein synthesis. The involvement of protein synthesis in the entrainment pathways, together with the findings that brief treatments of inhibitors of protein synthesis phase shift the rhythm and that continuous treatments of these inhibitors alter the period of the rhythm, indicates that translation is part of the oscillator mechanism. Recent evidence indicates that transcription may also be part of the oscillator mechanism. Brief treatments with DRB, a reversible transcription inhibitor, phase shift the rhythm while continuous treatments with DRB lengthen the period of the rhythm. A comparison of the effects of transcription and translation inhibitors on the rhythm indicates that transcription and translation are closely coupled in the eye circadian system. To know the precise role of transcription and translation in the circadian system, it is necessary to identify and then study specific proteins and mRNAs important for circadian timing. To identify putative oscillator proteins (POPs), we have hunted for proteins whose synthesis or phosphorylation was altered by the entraining agents light and 5-HT and by other agents that perturb the circadian rhythm. By exposing eyes to labeled amino acids in the presence of phase-shifting treatments and then using two-dimensional gel electrophoresis to separate proteins, we found eight proteins that may be considered POPs. To elucidate the cellular function of POPs, we have begun to obtain their amino acid sequences. A 40,000, pI 5.6 protein (POP-1) was identified as a member of the lipocortin family of proteins. Lipocortins are Ca(2+)-phospholipid binding proteins whose functions include inhibition of PLA2.(ABSTRACT TRUNCATED AT 400 WORDS)
Authors:
C Koumenis; A Eskin
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Chronobiology international     Volume:  9     ISSN:  0742-0528     ISO Abbreviation:  Chronobiol. Int.     Publication Date:  1992 Jun 
Date Detail:
Created Date:  1992-07-30     Completed Date:  1992-07-30     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8501362     Medline TA:  Chronobiol Int     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  201-21     Citation Subset:  IM    
Affiliation:
Department of Biochemical and Biophysical Sciences, University of Houston, TX 77204-5934.
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MeSH Terms
Descriptor/Qualifier:
Animals
Aplysia / physiology*
Circadian Rhythm / genetics,  physiology*,  radiation effects
Eye / radiation effects
Light
Ocular Physiological Phenomena
Protein Biosynthesis
Serotonin / physiology
Transcription, Genetic
Grant Support
ID/Acronym/Agency:
MH 41979/MH/NIMH NIH HHS
Chemical
Reg. No./Substance:
50-67-9/Serotonin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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