MiR-132 Regulates Rem Expression in Cardiomyocytes During Long-Term β-Adrenoceptor Agonism.
OBJECTIVE
To characterize the effects of long-term β-adrenergic receptor stimulation on Rem protein and mRNA expression in rat heart and possible involvement of miR-132.


METHODS
Adult rats were treated with isoproterenol (ISO, 150 µg.kg.h(-1)) for 2 d and Rem, miR-132, and α1c (the principal subunit of Cav1.2 channels) were measured at protein and mRNA levels with western blot and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) experiments, respectively. Ca(2+) currents and intracellular Ca(2+) signals were evaluated in isolated cardiomyocytes.


RESULTS
Systemic administration of ISO led to decreases in Rem protein and mRNA levels (down to 49%). Furthermore, levels of the microRNAs (miRs) miR-132 and miR-214 were upregulated 5- and 9-fold, respectively. Transfection of miR-132, but not miR-214, into HEK293 cells reduced the expression of a luciferase reporter gene controlled by a conserved 3´-untranslated region (UTR) of Rem by half. Chronic ISO administration also led to a 25% decrease in the amplitude of peak L-type Ca(2+) currents, a 40% decrease in α1c subunit protein abundance at the membrane level, and a 60% decrease in expression of α1c channel subunit mRNA.


CONCLUSIONS
These results suggest that Rem expression is down-regulated posttranscriptionally by miR-132 in response to long-term activation of β-adrenergic signaling, but this down-regulation does not produce a larger Ca(2+) influx through Cav1.2 channels.
Departamento de Farmacología. Centro de Investigación y de Estudios Avanzados del I.P.N. México, D.F. 07360. México.
Elba D
ED
Carrillo
Raúl
R
Sampieri
Ascención
A
Hernández
María C
MC
García
Jorge A
JA
Sánchez
D020413:3' Untranslated Regions / Q000187:drug effects; D000318:Adrenergic beta-Agonists / Q000008:administration & dosage* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D007545:Isoproterenol / Q000008:administration & dosage* / Q000494:pharmacology; D008297:Male; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D020413:3' Untranslated Regions; D000318:Adrenergic beta-Agonists; C548144:MIRN124 microRNA, rat; C548821:MIRN132 microRNA, rat; D035683:MicroRNAs; C108135:Rem protein, mouse; D020559:Monomeric GTP-Binding Proteins; D007545:Isoproterenol; D002118:Calcium