Beating affects the posttranscriptional regulation of alpha-myosin mRNA in cardiac cultures.
Contractile arrest of cardiac myocytes results in increased abundance of alpha-myosin heavy chain (MHC) mRNA but decreased alpha-MHC protein content. Our aim is to determine the posttranscriptional mechanisms regulating alpha-MHC mRNA-protein uncoupling in cultured neonatal rat hearts during altered contractile activity. Spontaneously contracting myocytes were arrested by the use of verapamil (10 mumol/l; a Ca(2+)-channel blocker) or by 2,3-butanedione monoxime (5 mmol/l; a cross-bridge inhibitor). Inhibition of transcription with amanitin (0.5 mumol/l) decreased the alpha-MHC mRNA in normally beating myocytes to a minimal baseline. However, the alpha-MHC mRNA did not fall this low in amanitin-treated nonbeating myocytes. Concurrently, the alpha-MHC mRNA shifted toward a heavier polysome complex when beating was blocked. Together, these data suggest that contractile arrest regulates alpha-MHC mRNA abundance posttranscriptionally by stabilizing the message at the elongation phase of translation. These posttranscriptional regulatory steps are dependent on beating itself and are independent of Ca2+ entry.
Goldspink
P H
PH
Department of Physiology and Biophysics, University of Illinois College of Medicine at Chicago 60612-7342, USA.
Thomason
D B
DB
Russell
B
B
D000818:Animals; D002478:Cells, Cultured; D003931:Diacetyl / Q000031:analogs & derivatives / Q000494:pharmacology; D004355:Drug Stability; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000235:genetics; D009218:Myosins / Q000235:genetics*; D011132:Polyribosomes / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
D012333:RNA, Messenger; C004717:diacetylmonoxime; D018995:Myosin Heavy Chains; D009218:Myosins; D003931:Diacetyl