Involvement of proteins in light resetting ocular circadian oscillators of Aplysia

Area of Science:

• Chronobiology
• Molecular Biology
• Circadian Rhythms

Background:

• Circadian rhythms are endogenous biological processes influenced by external cues like light.
• The molecular mechanisms by which light exerts its phase-shifting effects on circadian rhythms are not fully understood.
• Protein synthesis is a potential mediator of light's influence on circadian timing.

Purpose of the Study:

• To investigate the role of protein synthesis in mediating light-induced phase shifts of circadian rhythms.
• To identify specific proteins whose synthesis is affected by light pulses and other phase-shifting stimuli.
• To explore the relationship between light, protein synthesis, and the circadian system.

Main Methods:

• Inhibition of protein synthesis using anisomycin and cycloheximide.
• Analysis of amino acid incorporation into proteins via two-dimensional gel electrophoresis.
• Treatment with elevated extracellular potassium, 8-bromo-cyclic guanosine monophosphate (cGMP), and serotonin (5-HT) to mimic or interact with light effects.

Main Results:

• Protein synthesis inhibitors blocked light-induced advance phase shifts, supporting a role for protein synthesis.
• Light pulses altered amino acid incorporation into 11 proteins, with 9 showing phase-dependent changes.
• Elevated potassium, 8-bromo-cGMP, and serotonin also modulated protein synthesis, with significant overlap in affected proteins.
• Light's effects on some proteins were long-lasting or delayed, indicating complex regulatory processes.

Conclusions:

• Light appears to phase shift circadian rhythms, at least in part, by altering the synthesis of specific proteins.
• Several identified proteins are potential components of the circadian system, involved in entrainment or oscillator mechanisms.
• The findings provide molecular candidates for understanding how light signals are transduced to regulate circadian timing.