Suppression of FoxO1 mRNA by β2 -adrenoceptor-cAMP signaling through miR-374b-5p and miR-7a-1-3p in C2C12 myotubes.

Abstract

β2‐Adrenoceptor (β2‐AR) signaling decreases the transcriptional activity of forkhead box O (FoxO), but the underlying mechanisms remain incompletely understood. Here, we investigated how β2‐AR signaling regulates the protein abundance of FoxO and its transcriptional activity in skeletal muscle. We observed that stimulation of β2‐AR with its selective agonist, clenbuterol, rapidly decreased FoxO1 mRNA expression, and this was accompanied by a decrease in either FoxO1 protein level or FoxO transcriptional activity. We subsequently observed that miR‐374b‐5p and miR‐7a‐1‐3p were rapidly upregulated in response to β2‐AR stimulation. Transfection with mimics of either miRNA successfully decreased FoxO1 mRNA. Moreover, because β2‐AR stimulation increased cAMP concentration, pretreatment with an adenylyl cyclase inhibitor canceled out these effects of β2‐AR stimulation. These results suggest that β2‐AR stimulation results in rapid upregulation of miR‐374b‐5p and miR‐7a‐1‐3p in myotubes, which in turn results in a decrease in FoxO1 mRNA expression via the β2‐AR–cAMP signaling pathway.