Voltage-dependent anion channel 2 modulates resting Ca²+ sparks, but not action potential-induced Ca²+ signaling in cardiac myocytes.

Abstract

Voltage-dependent anion channels (VDACs) are pore forming proteins predominantly found in the outer mitochondrial membrane and are thought to transport Ca(2+). In this study, we have investigated the possible role of type 2 VDAC (VDAC2) in cardiac Ca(2+) signaling and Ca(2+) sparks using a lentiviral knock-down (KD) technique and two-dimensional confocal Ca(2+) imaging in immortalized autorhythmic adult atrial cells, HL-1. We confirmed high expression of VDAC2 protein in ventricular, atrial, and HL-1 cells using Western blot analysis. Infection of HL-1 cells with VDAC2-targeting lentivirus reduced the level of VDAC2 protein to ∼10%. Comparisons of autorhythmic Ca(2+) transients between wild-type (WT) and VDAC2 KD cells showed no significant change in the magnitude, decay, and beating rate of the Ca(2+) transients. Caffeine (10mM)-induced Ca(2+) release, which indicates sarcoplasmic reticulum (SR) Ca(2+) content, was not altered by VDAC2 KD. Interestingly, however, the intensity, width, and duration of the individual Ca(2+) sparks were significantly increased by VDAC2 KD in resting conditions, with no change in the frequency of sparks. VDAC2 KD significantly delayed mitochondrial Ca(2+) uptake during artificial Ca(2+) pulses in permeabilized HL-1 cells. These results suggest that VDAC2 may facilitate mitochondrial Ca(2+) uptake and restrict Ca(2+) spark expansion without regulating activations of sparks under resting conditions, thereby providing evidence on the functional role of VDAC2 in cardiac local Ca(2+) signaling.

• Authors: Krishna Prasad Subedi, Joon-Chul Kim, Moonkyung Kang, Min-Jeong Son, Yeon-Soo Kim, Sun-Hee Woo
• Journal: Cell calcium (Cell Calcium) Vol. 49 Issue 2 Pg. 136-43 (Feb 2011) ISSN: 1532-1991 [Electronic] Netherlands
• PMID: 21241999 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2010 Elsevier Ltd. All rights reserved.

Chemical References

• RNA, Small Interfering
• Voltage-Dependent Anion Channel 2
• Caffeine
• Calcium

Topics

• Action Potentials
• Animals
• Caffeine (pharmacology)
• Calcium (metabolism)
• Calcium Signaling (physiology)
• Cell Line, Transformed
• Mice
• Myocytes, Cardiac (cytology, metabolism)
• RNA Interference
• RNA, Small Interfering (metabolism)
• Sarcoplasmic Reticulum (metabolism)
• Voltage-Dependent Anion Channel 2 (genetics, metabolism)