title: Zinc-Induced Effects on Osteoclastogenesis Involves Activation of Hyperpolarization-Activated Cyclic Nucleotide Modulated Channels via Changes in Membrane Potential.
abstract: Zinc is a trace element in the mammalian body, and increasing evidence shows its critical role in bone development and osteoclastogenesis. The relationships between zinc and voltage-gated ion channels have been reported; however, the effects of zinc on membrane potential and the related ion channels remain unknown. In this study, we found that zinc-induced hyperpolarization in RAW264.7 cells (RAW) was promoted by inhibition of hyperpolarization-activated cyclic nucleotide modulated channels (HCNs). In electrophysiological experiments with RAW-derived osteoclasts, HCNs were functional and generated hyperpolarization-activated inward currents (Ih) with properties similar to the Ih recorded in excitable cells such as neurons and cardiomyocytes. Quantitative PCR of HCN subunits HCN1 and HCN4 in RAW cells showed detectable levels of HCN1 mRNA and HCN4 expression was the highest of all four subunits. HCN4 knockdown decreased osteoclastic Ih and promoted osteoclastogenesis in the presence of zinc, but not in the absence of zinc. To determine the effect of membrane hyperpolarization on osteoclastogenesis, we developed a light-controllable membrane potential system in RAW cells by stably expressing the light-driven outward proton pump, Archaerhodopsin3 (Arch). Arch activation by yellow-green light hyperpolarizes the cell membrane. Light-induced hyperpolarization accelerated osteoclast differentiation in the presence of receptor activator of nuclear factor kappa-B ligand (RANKL). Thus, HCN activation reduced the hyperpolarization-related promotion of osteoclast differentiation in the presence of zinc. This study revealed the novel role of HCN and membrane potential in non-excitable osteoclasts.
authors.affiliation: The Mellanby Centre for Bone Research, Department of Human Metabolism, University of Sheffield, Sheffield, UK.|Department of Physiology, Graduate School of Medicine, Osaka City University, Osaka, Japan.|Department of Molecular Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.|Global Center of Excellence Program for Molecular Science for Tooth and Bone Diseases, Tokyo Medical and Dental University, Tokyo, Japan.|Department of Pharmacology, Osaka Dental University, Osaka, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Notomi
authors.affiliation: Department of Physiology, Graduate School of Medicine, Osaka City University, Osaka, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Kuno
authors.affiliation: Department of Pharmacology, Osaka Dental University, Osaka, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Hiyama
authors.affiliation: Department of Pharmacology, Osaka Dental University, Osaka, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Ohura
authors.affiliation: Department of Molecular Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.|Global Center of Excellence Program for Molecular Science for Tooth and Bone Diseases, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Noda
authors.affiliation: The Mellanby Centre for Bone Research, Department of Human Metabolism, University of Sheffield, Sheffield, UK.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Skerry
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002462:Cell Membrane; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000378:metabolism*; D004594:Electrophysiology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008027:Light; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology*; D053245:RANK Ligand / Q000378:metabolism; D014131:Trace Elements / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; D053245:RANK Ligand; C505689:Tnfsf11 protein, mouse; D014131:Trace Elements; D049452:Green Fluorescent Proteins; D015032:Zinc
keywords: HYPERPOLARIZATION; ION CHANNEL; OSTEOCLAST