S100A1 enhances the L-type Ca2+ current in embryonic mouse and neonatal rat ventricular cardiomyocytes.
S100A1 is an EF-hand type Ca2+-binding protein with a muscle-specific expression pattern. The highest S100A1 protein levels are found in cardiomyocytes, and it is expressed already at day 8 in the heart during embryonic development. Since S100A1 is known to be involved in the regulation of Ca2+ homeostasis, we tested whether extracellular S100A1 plays a role in regulating the L-type Ca2+ current (I(Ca)) in ventricular cardiomyocytes. Murine embryonic (day 16.5 postcoitum) ventricular cardiomyocytes were incubated with S100A1 (0.001-10 microM) for different time periods (20 min to 48 h). I(Ca) density was found to be significantly increased as early as 20 min (from -10.8 +/- 1 pA/pF, n = 18, to -22.9 +/- 1.4 pA/pF; +112.5 +/- 13%, n = 9, p < 0.001) after the addition of S100A1 (1 microM). S100A1 also enhanced I(Ca) current density in neonatal rat cardiomyocytes. Fluorescence and capacitance measurements evidenced a fast translocation of rhodamine-coupled S100A1 from the extracellular space into cardiomyocytes. S100A1 treatment did not affect cAMP levels. However, protein kinase inhibitor, a blocker of cAMP-dependent protein kinase A (PKA), abolished the S100A1-induced enhancement of I(Ca). Accordingly, measurements of PKA activity yielded a significant increase in S100A1-treated cardiomyocytes. In vitro reconstitution assays further demonstrated that S100A1 enhanced PKA activity. We conclude that the Ca2+-binding protein S100A1 augments transsarcolemmal Ca2+ influx via an increase of PKA activity in ventricular cardiomyocytes and hence represents an important regulator of cardiac function.
Reppel
Michael
M
Institute of Neurophysiology, University of Cologne, Cologne 50931, Germany. michael.reppel@uni-koeln.de
Sasse
Philipp
P
Piekorz
Roland
R
Tang
Ming
M
Roell
Wilhelm
W
Duan
Yaqi
Y
Kletke
Anja
A
Hescheler
Jürgen
J
Nürnberg
Bernd
B
Fleischmann
Bernd K
BK
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000737:chemistry*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004594:Electrophysiology; D004705:Endocytosis; D007700:Kinetics; D051379:Mice; D009132:Muscles / Q000166:cytology; D032383:Myocytes, Cardiac / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D012235:Rhodamines / Q000494:pharmacology; D009418:S100 Proteins; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence; D013997:Time Factors
D020746:Calcium Channels, L-Type; D002135:Calcium-Binding Proteins; D012235:Rhodamines; D009418:S100 Proteins; C110294:S100A1 protein; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium