MicroRNA-433 Dampens Glucocorticoid Receptor Signaling, Impacting Circadian Rhythm and Osteoblastic Gene Expression

• Published in: The Journal of biological chemistry Vol. 291; no. 41; pp. 21717 - 21728
• Main Authors: Smith, Spenser S., Dole, Neha S., Franceschetti, Tiziana, Hrdlicka, Henry C., Delany, Anne M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 07.10.2016; American Society for Biochemistry and Molecular Biology
• Subjects: 3' Untranslated Regions - physiology; Animals; bone; circadian; circadian rhythm; Circadian Rhythm - physiology; Core Binding Factor Alpha 1 Subunit - genetics; Core Binding Factor Alpha 1 Subunit - metabolism; Gene Expression Regulation - physiology; Gene Regulation; glucocorticoid receptor; Hypoxia-Inducible Factor 1, alpha Subunit - biosynthesis; Hypoxia-Inducible Factor 1, alpha Subunit - genetics; Insulin-Like Growth Factor I - biosynthesis; Insulin-Like Growth Factor I - genetics; Male; Mice; Mice, Transgenic; microRNA (miRNA); microRNA mechanism; MicroRNAs - biosynthesis; MicroRNAs - genetics; osteoblast; Osteoblasts - cytology; Osteoblasts - metabolism; Osteocalcin - biosynthesis; Osteocalcin - genetics; Period Circadian Proteins - biosynthesis; Period Circadian Proteins - genetics; post-transcriptional regulation; Receptors, Glucocorticoid - genetics; Receptors, Glucocorticoid - metabolism; Signal Transduction - physiology; Skull - cytology; Skull - metabolism; circadian; glucocorticoid receptor; microRNA (miRNA); microRNA mechanism; post-transcriptional regulation; circadian rhythm; bone; osteoblast
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M116.737890

Serum glucocorticoids play a critical role in synchronizing circadian rhythm in peripheral tissues, and multiple mechanisms regulate tissue sensitivity to glucocorticoids. In the skeleton, circadian rhythm helps coordinate bone formation and resorption. Circadian rhythm is regulated through transcriptional and post-transcriptional feedback loops that include microRNAs. How microRNAs regulate circadian rhythm in bone is unexplored. We show that in mouse calvaria, miR-433 displays robust circadian rhythm, peaking just after dark. In C3H/10T1/2 cells synchronized with a pulse of dexamethasone, inhibition of miR-433 using a tough decoy altered the period and amplitude of Per2 gene expression, suggesting that miR-433 regulates rhythm. Although miR-433 does not directly target the Per2 3′-UTR, it does target two rhythmically expressed genes in calvaria, Igf1 and Hif1α. miR-433 can target the glucocorticoid receptor; however, glucocorticoid receptor protein abundance was unaffected in miR-433 decoy cells. Rather, miR-433 inhibition dramatically enhanced glucocorticoid signaling due to increased nuclear receptor translocation, activating glucocorticoid receptor transcriptional targets. Last, in calvaria of transgenic mice expressing a miR-433 decoy in osteoblastic cells (Col3.6 promoter), the amplitude of Per2 and Bmal1 mRNA rhythm was increased, confirming that miR-433 regulates circadian rhythm. miR-433 was previously shown to target Runx2, and mRNA for Runx2 and its downstream target, osteocalcin, were also increased in miR-433 decoy mouse calvaria. We hypothesize that miR-433 helps maintain circadian rhythm in osteoblasts by regulating sensitivity to glucocorticoid receptor signaling.