TY - JOUR
T1 - L-type calcium channel activity in osteoblast cells is regulated by the actin cytoskeleton independent of protein trafficking
AU - Li, Fangping
AU - Wang, Wenwei
AU - Gu, Ming
AU - Gyoneva, Stefka
AU - Zhang, Jie
AU - Huang, Shiying
AU - Traynelis, Stephen F.
AU - Cai, Hui
AU - Guggino, Sandra E.
AU - Zhang, Xuemei
N1 - Funding Information:
This project was supported by the National Nature Science Foundation of China (Grant no. 30600108) and NIH grant DK43423 to Sandra Guggino. NIH pharmacological science training grant T32 GM008602 to Stefka Gyoneva.
PY - 2011/9
Y1 - 2011/9
N2 - Voltage-dependent L-type calcium channels (VDCC) play important roles in many cellular processes. The interaction of the actin cytoskeleton with the channel in nonexcitable cells is less well understood. We performed whole-cell patch-clamp surface biotinylation and calcium imaging on different osteoblast cells to determine channel kinetics, amplitude, surface abundance, and intracellular calcium, respectively. Patch-clamp studies showed that actin polymerization by phalloidin increased the peak current density of I Ca, whereas actin depolymerization by cytochalasin D (CD) significantly decreased the current amplitude. This result is consistent with calcium imaging, which showed that CD significantly decreased Bay K8644-induced intracellular calcium increase. Surface biotinylation studies showed that CD is not able to affect the surface expression of the pore-forming subunit α 1C. Interestingly, application of CD caused a significantly negative shift in the steady-state inactivation kinetics of I Ca. There were decreases in the voltage at half-maximal inactivation that changed in a dosedependent manner. CD also reduced the effect of activated vitamin D 3 (1α,25-D3) on VDCC and intracellular calcium. Weconclude that in osteoblasts the actin cytoskeleton affects α 1C by altering the channel kinetic properties, instead of changing the surface expression, and it is able to regulate 1α,25-D3 signaling through VDCC. Our study provides a new insight into calcium regulation in osteoblasts, which are essential in many physiological functions of this cell.
AB - Voltage-dependent L-type calcium channels (VDCC) play important roles in many cellular processes. The interaction of the actin cytoskeleton with the channel in nonexcitable cells is less well understood. We performed whole-cell patch-clamp surface biotinylation and calcium imaging on different osteoblast cells to determine channel kinetics, amplitude, surface abundance, and intracellular calcium, respectively. Patch-clamp studies showed that actin polymerization by phalloidin increased the peak current density of I Ca, whereas actin depolymerization by cytochalasin D (CD) significantly decreased the current amplitude. This result is consistent with calcium imaging, which showed that CD significantly decreased Bay K8644-induced intracellular calcium increase. Surface biotinylation studies showed that CD is not able to affect the surface expression of the pore-forming subunit α 1C. Interestingly, application of CD caused a significantly negative shift in the steady-state inactivation kinetics of I Ca. There were decreases in the voltage at half-maximal inactivation that changed in a dosedependent manner. CD also reduced the effect of activated vitamin D 3 (1α,25-D3) on VDCC and intracellular calcium. Weconclude that in osteoblasts the actin cytoskeleton affects α 1C by altering the channel kinetic properties, instead of changing the surface expression, and it is able to regulate 1α,25-D3 signaling through VDCC. Our study provides a new insight into calcium regulation in osteoblasts, which are essential in many physiological functions of this cell.
KW - Actin cytoskeleton
KW - Depolymerization
KW - Osteoblast
KW - Polymerization
KW - Voltage-dependent L-type calcium channel
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U2 - 10.1007/s00774-010-0252-6
DO - 10.1007/s00774-010-0252-6
M3 - Article
C2 - 21246227
AN - SCOPUS:83155184573
SN - 0914-8779
VL - 29
SP - 515
EP - 525
JO - Journal of Bone and Mineral Metabolism
JF - Journal of Bone and Mineral Metabolism
IS - 5
ER -