IA Channels Encoded by Kv1.4 and Kv4.2 Regulate Circadian Period of PER2 Expression in the Suprachiasmatic Nucleus. (October 2015)

• Record Type: Journal Article
• Authors: Granados-Fuentes, Daniel; Hermanstyne, Tracey O.; Carrasquillo, Yarimar; Nerbonne, Jeanne M.; Herzog, Erik D.
• Is Part Of: Journal of biological rhythms. Volume 30:Number 5(2015:Oct.)
• Page Start: 396
• Page End: 407
• Publication Date: 2015-10
• Subjects: clock gene expression -- A-type K+ channels -- entrainment -- periodicity; Biological rhythms -- Periodicals; Circadian rhythms -- Periodicals; 571.77
• DOI: 10.1177/0748730415593377
• Languages: English
• ISSNs: 0748-7304

Abstract

Neurons in the suprachiasmatic nucleus (SCN), the master circadian pacemaker in mammals, display daily rhythms in electrical activity with more depolarized resting potentials and higher firing rates during the day than at night. Although these daily variations in the electrical properties of SCN neurons are required for circadian rhythms in physiology and behavior, the mechanisms linking changes in neuronal excitability to the molecular clock are not known. Recently, we reported that mice deficient for either Kcna4 ( Kv1.4 -/- ) or Kcnd2 ( Kv4.2 -/- ; but not Kcnd3, Kv4.3 -/- ), voltage-gated K + (Kv) channel pore-forming subunits that encode subthreshold, rapidly activating, and inactivating K + currents (IA ), have shortened (0.5 h) circadian periods in SCN firing and in locomotor activity compared with wild-type (WT) mice. In the experiments here, we used a mouse ( Per2 Luc ) line engineered with a bioluminescent reporter construct, PERIOD2::LUCIFERASE (PER2::LUC), replacing the endogenous Per2 locus, to test the hypothesis that the loss of Kv1.4- or Kv4.2-encoded IA channels also modifies circadian rhythms in the expression of the clock protein PERIOD2 (PER2). We found that SCN explants from Kv1.4 -/- Per2 Luc and Kv4.2 -/- Per2 Luc, but not Kv4.3 -/- Per2 Luc, mice have significantly shorter (by approximately 0.5 h) circadian periods in PER2 rhythms, compared with explants from Per2 Luc mice, revealing that the membrane properties of SCN neurons feedback to regulate clock (PER2) expression. The combined loss of both Kv1.4- and Kv4.2-encoded IA channels in Kv1.4 -/- /Kv4.2 -/- Per2 Luc SCN explants did not result in any further alterations in PER2 rhythms. Interestingly, however, mice lacking both Kv1.4 and Kv4.2 show a striking (approximately 1.8 h) advance in their daily activity onset in a light cycle compared with WT mice, suggesting additional roles for Kv1.4- and Kv4.2-encoded IA channels in controlling the light-dependent responses of neurons within and/or outside of the SCN to regulate circadian phase of daily activity.