Role of gelsolin in the actin filament regulation of cardiac L-type calcium channels

ALAN S. LADER, DAVID J. KWIATKOWSKI AND HORACIO F. CANTIELLO

AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY

Año: 1999 p. 1277 - 1283

0363-6143

The actin cytoskeleton is an important contributor to the modulation of the cell function. However, little is known about the regulatory role of this supermolecular structure in the membrane events that take place in the heart. In this report, the regulation of cardiac myocyte function by actin filament organization was investigated in neonatal mouse cardiac myocytes (NMCM) from both wild-type mice and mice genetically devoid of the actin filament severing protein gelsolin (Gsn2/2). Cardiac L-type calcium channel currents (ICa) were assessed using the whole cell voltage-clamp technique. Addition of the actin filament stabilizer phalloidin to wild-type NMCM increased ICa by 227% over control conditions. The basal ICa of Gsn2/2 NMCM was 300% higher than wild-type controls. This increase was completely reversed by intracellular perfusion of the Gsn2/2 NMCM with exogenous gelsolin. Further, cytoskeletal disruption of either Gsn2/2 or phalloidin-dialyzed wild-type NMCM with cytochalasin D (CD) decreased the enhanced ICa by 84% and 87%, respectively. The data indicate that actin filament stabilization by either a lack of gelsolin or intracellular dialysis with phalloidin increase ICa, whereas actin filament disruption with CD or dialysis of Gsn2/2 NMCM with gelsolin decrease ICa. We conclude that cardiac L-type calcium channel regulation is tightly controlled by actin filament organization. Actin filament rearrangement mediated by gelsolin may contribute to calcium channel inactivation. The actin cytoskeleton is an important contributor to the modulation of the cell function. However, little is known about the regulatory role of this supermolecular structure in the membrane events that take place in the heart. In this report, the regulation of cardiac myocyte function by actin filament organization was investigated in neonatal mouse cardiac myocytes (NMCM) from both wild-type mice and mice genetically devoid of the actin filament severing protein gelsolin (Gsn2/2). Cardiac L-type calcium channel currents (ICa) were assessed using the whole cell voltage-clamp technique. Addition of the actin filament stabilizer phalloidin to wild-type NMCM increased ICa by 227% over control conditions. The basal ICa of Gsn2/2 NMCM was 300% higher than wild-type controls. This increase was completely reversed by intracellular perfusion of the Gsn2/2 NMCM with exogenous gelsolin. Further, cytoskeletal disruption of either Gsn2/2 or phalloidin-dialyzed wild-type NMCM with cytochalasin D (CD) decreased the enhanced ICa by 84% and 87%, respectively. The data indicate that actin filament stabilization by either a lack of gelsolin or intracellular dialysis with phalloidin increase ICa, whereas actin filament disruption with CD or dialysis of Gsn2/2 NMCM with gelsolin decrease ICa. We conclude that cardiac L-type calcium channel regulation is tightly controlled by actin filament organization. Actin filament rearrangement mediated by gelsolin may contribute to calcium channel inactivation.