title: Hypotonicity activates a voltage-dependent membrane conductance in N2a neuroblastoma cells.
abstract: To maintain cellular and bodily homeostasis, cells respond to extracellular stimuli including osmotic stress by activating various ion channels, which have been implicated in many physiological and pathophysiological conditions. However, cellular osmosensory mechanisms remain elusive. Here, we report a novel voltage-dependent current in N2a cells activated by exposure to hypotonic stress. After a hypotonic challenge, N2a cells sequentially develop two distinct currents. The volume-regulated anion channel (VRAC) current emerges first and, after a delay, activation of a previously uncharacterized strongly outwardly rectifying current follows. The latter, delayed current (Id) is insensitive to NPPB, a nonspecific blocker of Cl-channels, and intracellular Mg2+, which inhibits VRAC and swelling-activated TRPM3 and TRPM7 channels. Replacement of extracellular Na+with NMDG+reduces inward tail currents, suggesting that Idis mediated by cations. Finally, Idshows voltage-dependent activation with slow activation kinetics and half-maximal activation at +76 mV. These pharmacological and biophysical characteristics of Idare distinct from those of known osmotic cell swelling-activated ion channels. In conclusion, our data identify and characterize a novel osmotically-activated, voltage-dependent ion channel in N2a cells.
authors.affiliation: Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto 602-8566, Japan. Electronic address: taruno@koto.kpu-m.ac.jp.
authors.forename: Akiyuki
authors.initials: A
authors.lastname: Taruno
authors.affiliation: Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto 602-8566, Japan; Department of Bio-Ionomics, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto 602-8566, Japan. Electronic address: marunaka@koto.kpu-m.ac.jp.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Marunaka
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D015640:Ion Channel Gating; D007473:Ion Channels / Q000502:physiology; D051379:Mice; D009447:Neuroblastoma / Q000473:pathology / Q000503:physiopathology*; D009994:Osmolar Concentration
chemical_list: D007473:Ion Channels
keywords: Cell swelling; Hypotonic stress; Ion channel; Voltage-gated