title: The contribution of TWIK-1 channels to astrocyte K(+) current is limited by retention in intracellular compartments.
abstract: TWIK-1 two-pore domain K(+) channels are expressed abundantly in astrocytes. In the present study, we examined the extent to which TWIK-1 contributes to the linear current-voltage (I-V) relationship (passive) K(+) membrane conductance, a dominant electrophysiological feature of mature hippocampal astrocytes. Astrocytes from TWIK-1 knockout mice have a more negative resting potential than those from wild type animals and a reduction in both inward rectification and Cs(+) permeability. Nevertheless, the overall whole-cell passive conductance is not altered significantly in TWIK-1 knockout astrocytes. The expression of Kir4.1 and TREK-1, two other major astrocytic K(+) channels, or of other two-pore K(+) channels is not altered in TWIK-1 knockout mice, suggesting that the mild effect of TWIK-1 knockout does not result from compensation by these channels. Fractionation experiments showed that TWIK-1 is primarily localized in intracellular cytoplasmic fractions (55%) and mildly hydrophobic internal compartment fractions (41%), with only 5% in fractions containing plasma membranes. Our study revealed that TWIK-1 proteins are mainly located in the intracellular compartments of hippocampal astrocyte under physiological condition, therefore a minimal contribution of TWIK-1 channels to whole-cell currents is likely attributable to a relatively low level presence of channels in the plasma membrane.
authors.affiliation: Department of Neuroscience, The Ohio State University Wexner Medical Center Columbus, OH, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Neuroscience, The Ohio State University Wexner Medical Center Columbus, OH, USA.
authors.forename: Adhytia
authors.initials: A
authors.lastname: Putra
authors.affiliation: South Carolina College of Pharmacy Columbia, SC, USA.
authors.forename: Gary P
authors.initials: GP
authors.lastname: Schools
authors.affiliation: Department of Neuroscience, The Ohio State University Wexner Medical Center Columbus, OH, USA.
authors.forename: Baofeng
authors.initials: B
authors.lastname: Ma
authors.affiliation: Department of Biological Sciences, University at Albany, SUNY Albany, NY, USA.
authors.forename: Haijun
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Pharmacology, Yale University School of Medicine New Haven, CT, USA.
authors.forename: Leonard K
authors.initials: LK
authors.lastname: Kaczmarek
authors.affiliation: Centre National de la Recherche Scientifique, Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia Antipolis Valbonne, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Barhanin
authors.affiliation: Centre National de la Recherche Scientifique, Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia Antipolis Valbonne, France.
authors.forename: Florian
authors.initials: F
authors.lastname: Lesage
authors.affiliation: Department of Neuroscience, The Ohio State University Wexner Medical Center Columbus, OH, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Zhou
keywords: TWIK-1 potassium channel; astrocytes; patch clamp; qRT-PCR; western blot