Ras reduces L-type calcium channel current in cardiac myocytes. Corrective effects of L-channels and SERCA2 on [Ca(2+)](i) regulation and cell morphology.
Heart failure is associated with dysregulation of intracellular calcium ([Ca(2+)](i)), reduction in myofibrils, and increased activation of Ras, a regulator of signal-transduction pathways. To evaluate the potential effects of Ras on [Ca(2+)](i), we expressed constitutively active Ras (Ha-Ras(V12)) in cardiac myocytes and monitored [Ca(2+)](i) via fluorescence and electrophysiological techniques. Ha-Ras(V12) reduced the magnitude of the contractile calcium transients. Unexpectedly, however, calcium loading of the sarcoplasmic reticulum was increased, suggesting that Ha-Ras(V12) introduces a defect in excitation-calcium release coupling. Consistent with this idea, L-channel calcium currents were reduced by Ha-Ras(V12), which also downregulated the activity of the L-channel gene promoter. Coexpression of L-channels and SERCA2 largely corrected Ha-Ras(V12)-induced dysregulation of [Ca(2+)](i). Furthermore, whereas Ha-Ras(V12) downregulated myofibrils, this effect was blocked by coexpression of L-channels. These results suggest that Ras downregulates L-channel expression, which may play a pathophysiological role in cardiac disease.
Ho
P D
PD
SDSU Heart Institute and Department of Biology, San Diego State University, San Diego, California, USA.
Fan
J S
JS
Hayes
N L
NL
Saada
N
N
Palade
P T
PT
Glembotski
C C
CC
McDonough
P M
PM
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D048429:Cell Size; D002478:Cells, Cultured; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D009210:Myofibrils / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011189:Potassium Chloride / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D016276:Ventricular Function; D018631:ras Proteins / Q000235:genetics / Q000502:physiology*
C506948:Atp2a2 protein, rat; D020746:Calcium Channels, L-Type; D011993:Recombinant Fusion Proteins; D002110:Caffeine; D011189:Potassium Chloride; D008156:Luciferases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D018631:ras Proteins; D000252:Calcium-Transporting ATPases; D002118:Calcium