Evidence for Circadian Regulation of Activating Transcription Factor 5 But Not Tyrosine Hydroxylase by the Chromaffin Cell Clock

Sep 8, 2007Endocrinology

Daily rhythms control activating transcription factor 5 but not tyrosine hydroxylase in adrenal hormone-producing cells

AI simplified

Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

Rhesus monkey adrenal glands show a 24-hour rhythmic expression of several genes, including Atf5, a transcription factor linked to cell differentiation.

Core-clock genes may influence adrenal circadian function in chromaffin cells.
Serum shock in rat PC12 cells triggered rhythmic oscillation of several clock genes.
Atf5 expression exhibited circadian patterns, while the rate-limiting enzyme TH did not.
The BMAL1 protein is associated with regulating Atf5 by binding to its promoter.
In Bmal1-/- mice, Atf5 mRNA showed a diminished circadian rhythm in the liver.
Higher Atf5 levels were observed in both liver and adrenal glands of Bmal1-/- mice.

AI simplified

In mammals, adrenal medulla chromaffin cells constitute a fundamental component of the sympathetic nervous system outflow, producing most of the circulating adrenaline. We recently found that the rhesus monkey adrenal gland expresses several genes in a 24-h rhythmic pattern, including TH (the rate-limiting enzyme in catecholamine synthesis) and Atf5 (a transcription factor involved in apoptosis and neural cell differentiation) together with the core-clock genes. To examine whether these core-clock genes play a role in adrenal circadian function, we exposed rat pheochromocytoma PC12 cells to a serum shock and found that it triggered rhythmic oscillation of the clock genes rBmal1, rPer1, rRev-erbalpha, and rCry1 and induced the circadian expression of Atf5 but not TH. Furthermore, we found that the CLOCK/brain and muscle Arnt-like protein-1 (BMAL1) heterodimer could regulate Atf5 expression by binding to an E-box motif and repressing activity of its promoter. The physiological relevance of this interaction was evident in Bmal1 -/- mice, in which blunted circadian rhythm of Atf5 mRNA was observed in the liver, together with significantly higher expression levels in both liver and adrenal glands. Although we found no compelling evidence for rhythmic expression of TH in chromaffin cells being regulated by an intrinsic molecular clock mechanism, the Atf5 results raise the possibility that other aspects of chromaffin cell physiology, such as cell survival and cell differentiation, may well be intrinsically regulated.

Full Text

Full text is available at the source.

View full text (PDF) ↗View full text ↗

Evidence for Circadian Regulation of Activating Transcription Factor 5 But Not Tyrosine Hydroxylase by the Chromaffin Cell Clock

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief

Abstract

Full Text

Related papers

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief