title: Circadian rhythm of enolase in suprachiasmatic nucleus depends on mitochondrial function.
abstract: Metabolic activity in the suprachiasmatic nucleus (SCN), a center of biological rhythm, is higher during the daytime than at night. The rhythmic oscillation in the SCN is feedback controlled by the CLOCK/BMAL1 heterodimer binding to the E-box in target genes (e.g., Arg- vasopressin). Similar transcriptional regulation by NPAS2/BMAL1 heterodimer formation operates in the brain, which depends on the redox state (i.e., NAD/NADH). To clarify the metabolic function of SCN in relation to the redox state, two-dimensional electrophoresis was carried out on the mitochondrial fraction of SCN, obtained from rats kept under a light:dark cycle and constant under dim light. The electrophoretic pattern with TOF-mass spectrometry analysis revealed that enolase catalyzes the interconversion of 2-phosphoglycerate and phosphoenolpyruvate. The enolase activity, coupled with lactate dehydrogenase, was higher during the light period than that in the dark. However, enolase mRNA, analyzed by RT-PCR, showed higher levels during the dark period than in the light. The clock gene products Per2, Bmal1, Rev-erbα, and AVP mRNA in the mitochondrial fraction of SCN developed a circadian rhythm showing almost the same peak time as that in whole SCN. These mRNA rhythms ran free except for that of Rev-erbα mRNA. The results indicate that, in the glycolysis-related energy pathway, enolase might be involved in higher metabolic activity during the day than at night, at least in part.
authors.affiliation: Department of Neuro-Physiology and Brain Science, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan. yisobe@ med.nagoya-cu.ac.jp
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Isobe
authors.forename: Hideki
authors.initials: H
authors.lastname: Hida
authors.forename: Hitoo
authors.initials: H
authors.lastname: Nishino
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism / Q000648:ultrastructure; D002940:Circadian Rhythm / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000502:physiology*; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000502:physiology*; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism; D010751:Phosphopyruvate Hydratase / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018709:Statistics, Nonparametric; D013493:Suprachiasmatic Nucleus / Q000378:metabolism* / Q000648:ultrastructure*; D057825:Two-Dimensional Difference Gel Electrophoresis
chemical_list: D056950:Period Circadian Proteins; D012333:RNA, Messenger; D007770:L-Lactate Dehydrogenase; D010751:Phosphopyruvate Hydratase