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A CREB‐mediated increase in miRNA let‐7f during prolonged β‐agonist exposure: a novel mechanism of β 2 ‐adrenergic receptor down‐regulation in airway smooth muscle
Author(s) -
Kim Donghwa,
Cho Soomin,
Woo Jung A.,
Liggett Stephen B.
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.201701278r
Subject(s) - creb , agonist , receptor , tachyphylaxis , desensitization (medicine) , chemistry , gene knockdown , downregulation and upregulation , endocrinology , medicine , internalization , microbiology and biotechnology , biology , apoptosis , transcription factor , biochemistry , gene
β 2 ‐Adrenergic receptors (β 2 ARs) desensitize during continuous agonist activation, which manifests clinically as tachyphylaxis. β‐Agonist desensitization of β 2 ARs in human airway smooth muscle (HASM) cells is recognized in the treatment of asthma and maybe related to poor outcomes. Rapid events in desensitization include receptor phosphorylation and internalization, but mechanisms responsible for the decrease in receptor protein after prolonged agonist exposure (down‐regulation) are ill defined. The microRNA (miRNA) let‐7f regulates β 2 AR expression by translational repression. In cultured HASM cells from nonasthmatic and asthmatic lungs, 18 h of β‐agonist exposure increased let‐7 f by 2–3‐fold, concomitant with a ~90% decrease in β 2 ARs. Inhibition of let‐7f attenuated this down‐regulation response by ~50%. The let‐7 f increase was found to be cAMP/PKA‐dependent. The mechanism of the let‐7 f increase was found by chromatin immunoprecipitation to be from activated cAMP response element‐binding protein (CREB) binding to the let‐7f promoter, thereby increasing let‐7f expression. Knockdown of CREB attenuated agonist‐promoted β 2 AR down‐regulation by ~50%. Thus, β 2 AR down‐regulation occurs as a result of not only internalized receptor degradation but also a novel cAMP/PKA/CREB‐mediated increase in let‐7f which causes enhanced repression of the β 2 AR gene, adrenoreceptor β 2 (ADRB2) translation and represents ~50°% of the net loss of receptors observed after prolonged agonist exposure. This mechanism is apparent in asthmatic HASM cells, indicating relevance in a disease model.—Kim, D., Cho, S., Woo, J. A., Liggett, S.B. A CREB‐mediated increase in miRNA let‐7 f during prolonged β‐agonist exposure: a novel mechanism of β 2 ‐adrenergic receptor down‐regulation in airway smooth muscle. FASEB J. 32, 3680–3688 (2018). www.fasebj.org