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Am J Physiol Heart Circ Physiol (May 25, 2007). doi:10.1152/ajpheart.00450.2007
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Submitted on April 12, 2007
Accepted on May 21, 2007

Cav1.3 channels produce persistent calcium sparklets, but Cav1.2 channels are responsible for sparklets in mouse arterial smooth muscle

Manuel F. Navedo1, Gregory C. Amberg1, Ruth E. Westenbroek2, Martina J Sinnegger-Brauns3, William A. Catterall2, Joerg Striessnig3, and Luis F. Santana1*

1 Physiology & Biophysics, University of Washington, Seattle, Washington, United States
2 Pharmacology, University of Washington, Seattle, Washington, United States
3 Pharmacology & Toxicology, University of Innsbruck, Innsbruck, Austria

* To whom correspondence should be addressed. E-mail: santana{at}u.washington.edu.

Ca2+ sparklets are local elevations in intracellular Ca2+ produced by the opening of a single or a cluster of L-type Ca2+ channels. In arterial myocytes, Ca2+ sparklets regulate local and global intracellular Ca2+. At present, the molecular identity of the L-type Ca2+ channels underlying Ca2+ sparklets in these cells is undetermined. Here, we tested the hypotheses that Cav1.3 channels can produce Ca2+ sparklets and that Cav1.2 and/or Cav1.3 channels are responsible for Ca2+ sparklets in mouse arterial myocytes. First, we investigated the functional properties of single Cav1.3 channels in tsA-201 cells. With 110 mM Ba2+ as the charge carrier, Cav1.3 channels had a conductance of 20 pS. This value is similar to that of Cav1.2 and native L-type Ca2+ channels. As previously shown for Cav1.2 channels, Cav1.3 channels can operate in two gating modes characterized by short and long open times. Expressed Cav1.3 channels also produced Ca2+ sparklets. Cav1.3 sparklets had properties similar to those produced by Cav1.2 and native L-type channels including quantal amplitude, dihydropyridine sensitivity, bimodal gating, and dual event duration times. However, the voltage dependencies of conductance and steady-state inactivation of the Ca2+ current (ICa) in arterial myocytes were similar to those recorded from cells expressing Cav1.2, but not Cav1.3 channels. Furthermore, nifedipine (10 µM) eliminated Ca2+ sparklets in wild type myocytes, but not in myocytes expressing dihydropyridine-insensitive Cav1.2 channels. Accordingly, Cav1.3 transcript and protein were not detected in isolated arterial myocytes. We conclude that although Cav1.3 channels can produce Ca2+ sparklets, Cav1.2 channels underlie ICa, Ca2+ sparklets, and hence dihydropyridine-sensitive Ca2+ influx in mouse arterial myocytes.




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M. F. Navedo, M. Nieves-Cintron, G. C. Amberg, C. Yuan, V. S. Votaw, W. J. Lederer, G. S. McKnight, and L. F. Santana
AKAP150 Is Required for Stuttering Persistent Ca2+ Sparklets and Angiotensin II-Induced Hypertension
Circ. Res., February 1, 2008; 102(2): e1 - e11.
[Abstract] [Full Text] [PDF]




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