Light and Glutamate-Induced Degradation of the Circadian Oscillating Protein BMAL1 during the Mammalian Clock Resetting

• Published in: The Journal of neuroscience Vol. 20; no. 20; pp. 7525 - 7530
• Main Authors: Tamaru, Teruya, Isojima, Yasushi, Yamada, Takashi, Okada, Masato, Nagai, Katsuya, Takamatsu, Ken
• Format: Journal Article
• Language: English
• Published: United States Soc Neuroscience 15-10-2000; Society for Neuroscience
• Subjects: Animals; Antibodies - pharmacology; ARNTL Transcription Factors; Basic Helix-Loop-Helix Transcription Factors; Biological Clocks - drug effects; Biological Clocks - physiology; BMAL1 protein; Circadian Rhythm - drug effects; Circadian Rhythm - physiology; Darkness; Dose-Response Relationship, Drug; Glutamic Acid - metabolism; Glutamic Acid - pharmacology; Immunoblotting; In Vitro Techniques; Light; Male; N-Methylaspartate - metabolism; N-Methylaspartate - pharmacology; Organ Specificity; Photoperiod; Rats; Rats, Wistar; Suprachiasmatic Nucleus - drug effects; Suprachiasmatic Nucleus - metabolism; Tetrodotoxin - pharmacology; Transcription Factors - antagonists & inhibitors; Transcription Factors - metabolism
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/jneurosci.20-20-07525.2000

Recently discovered mammalian clock genes are believed to compose the core oscillator, which generates the circadian rhythm. BMAL1/CLOCK heterodimer is the essential positive element that drives clock-related transcription and self-sustaining oscillation by a negative feedback mechanism. We examined BMAL1 protein expression in the rat suprachiasmatic nuclei (SCN) by immunoblot analysis. Anti-BMAL1 antiserum raised against rBMAL1 recognized 70 kDa mBMAL1b and detected a similar immunoreactivity (IR) as a major band in rat brains. Robust circadian BMAL1-IR oscillations with nocturnal peaks were detected in the SCN during a light/dark cycle and under constant darkness. A short duration light exposure at night acutely reduced BMAL1-IR in the SCN during photoentrainment. This might be attributable to the degradation of BMAL1 protein. Application of glutamate and NMDA to the SCN slices at projected night, a procedure mimicking photic phase delay shift, also acutely reduced BMAL1-IR in a similar manner. A rapid decrease of BMAL1 protein suggests that BMAL1 protein might be implicated in the light-transducing pathway within the SCN.