Regulation of gap-junction protein connexin 43 by beta-adrenergic receptor stimulation in rat cardiomyocytes.
OBJECTIVE
beta-adrenergic receptor (beta-AR) agonists are among the most potent factors regulating cardiac electrophysiological properties. Connexin 43 (Cx43), the predominant gap-junction protein in the heart, has an indispensable role in modulating cardiac electric activities by affecting gap-junction function. The present study investigates the effects of short-term stimulation of beta-AR subtypes on Cx43 expression and gap junction intercellular communication (GJIC) function.


METHODS
The level of Cx43 expression in neonatal rat cardiomyocytes (NRCM) was detected by a Western blotting assay. The GJIC function was evaluated by scrape loading/dye transfer assay.


RESULTS
Stimulation of beta-AR by the agonist isoproterenol for 5 min induces the up-regulation of nonphosphorylated Cx43 protein level, but not total Cx43. Selective beta(2)-AR inhibitor ICI 118551, but not beta(1)-AR inhibitor CGP20712, could fully abolish the effect. Moreover, pretreatment with both protein kinase A inhibitor H89 and G(i) protein inhibitor pertussis toxin also inhibited the isoproterenol-induced increase of nonphosphorylated Cx43 expression. Isoproterenol-induced up-regulation of nonphosphorylated Cx43 is accompanied with enhanced GJIC function.


CONCLUSIONS
Taken together, beta(2)-AR stimulation increases the expression of nonphosphorylated Cx43, thereby enhancing the gating function of gap junctions in cardiac myocytes in both a protein kinase A- and G(i)-dependent manner.Acta Pharmacologica Sinica (2009) 30: 928-934; doi: 10.1038/aps.2009.92.
Xia
Yi
Y
Electrophysiology Laboratory, Department of Cardiology, Peking University People's Hospital, Beijing 100044, China.
Gong
Kai-Zheng
KZ
Xu
Ming
M
Zhang
You-Yi
YY
Guo
Ji-Hong
JH
Song
Yao
Y
Zhang
Ping
P
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D037342:Pertussis Toxin / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D018031:Connexin 43; D007093:Imidazoles; D020033:Protein Isoforms; D011943:Receptors, Adrenergic, beta; D011433:Propranolol; C049763:CGP 20712A; D037342:Pertussis Toxin; D017868:Cyclic AMP-Dependent Protein Kinases; C514014:Ppp2ca protein, rat; D054648:Protein Phosphatase 2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D007545:Isoproterenol