title: TRPV4 Contributes to Resting Membrane Potential in Retinal Müller Cells: Implications in Cell Volume Regulation.
abstract: Neural activity alters osmotic gradients favoring cell swelling in retinal Müller cells. This swelling is followed by a regulatory volume decrease (RVD), partially mediated by an efflux of KCl and water. The transient receptor potential channel 4 (TRPV4), a nonselective calcium channel, has been proposed as a candidate for mediating intracellular Ca2+elevation induced by swelling. We previously demonstrated in a human Müller cell line (MIO-M1) that RVD strongly depends on ion channel activation and, consequently, on membrane potential (Vm). The aim of this study was to investigate if Ca2+influx via TRPV4 contributes to RVD by modifying intracellular Ca2+concentration and/or modulating Vmin MIO-M1 cells. Cell volume, intracellular Ca2+levels, and Vmchanges were evaluated using fluorescent probes. Results showed that MIO-M1 cells express functional TRPV4 which determines the resting Vmassociated with K+channels. Swelling-induced increases in Ca2+levels was due to both Ca2+release from intracellular stores and Ca2+influx by a pathway alternative to TRPV4. TRPV4 blockage affected swelling-induced biphasic response (depolarization-repolarization), suggesting its participation in modulating Vmchanges during RVD. Agonist stimulation of Ca2+influx via TRPV4 activated K+channels hyperpolarizing Vmand accelerating RVD. We propose that TRPV4 forms a signaling complex with Ca2+and/or voltage-dependent K+channels to define resting Vmand Vmchanges during RVD. TRPV4 involvement in RVD depends on the type of stimuli and/or degree of channel activation, leading to a maximum RVD response when Ca2+influx overcomes a threshold and activates further signaling pathways in cell volume regulation. J. Cell. Biochem. 118: 2302-2313, 2017. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Laboratorio de Biomembranas, IFIBIO Houssay, CONICET-UBA, Departamento de Ciencia Fisiológicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Vanina
authors.initials: V
authors.lastname: Netti
authors.affiliation: Laboratorio de Biomembranas, IFIBIO Houssay, CONICET-UBA, Departamento de Ciencia Fisiológicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Juan
authors.initials: J
authors.lastname: Fernández
authors.affiliation: Laboratorio de Biomembranas, IFIBIO Houssay, CONICET-UBA, Departamento de Ciencia Fisiológicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Maia
authors.initials: M
authors.lastname: Kalstein
authors.affiliation: Laboratorio de Biomembranas, IFIBIO Houssay, CONICET-UBA, Departamento de Ciencia Fisiológicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Pizzoni
authors.affiliation: Laboratorio de Biomembranas, IFIBIO Houssay, CONICET-UBA, Departamento de Ciencia Fisiológicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Gisela
authors.initials: G
authors.lastname: Di Giusto
authors.affiliation: Laboratorio de Biomembranas, IFIBIO Houssay, CONICET-UBA, Departamento de Ciencia Fisiológicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Valeria
authors.initials: V
authors.lastname: Rivarola
authors.affiliation: Laboratorio de Biomembranas, IFIBIO Houssay, CONICET-UBA, Departamento de Ciencia Fisiológicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Paula
authors.initials: P
authors.lastname: Ford
authors.affiliation: Laboratorio de Biomembranas, IFIBIO Houssay, CONICET-UBA, Departamento de Ciencia Fisiológicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Claudia
authors.initials: C
authors.lastname: Capurro
mesh_terms: D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D063928:Ependymoglial Cells / Q000187:drug effects / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009025:Morpholines / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: C573308:HC-067047; D009025:Morpholines; C530602:N-(1-((4-(2-(((2,4-dichlorophenyl)sulfonyl)amino)-3-hydroxypropanoyl)-1-piperazinyl)carbonyl)-3-methylbutyl)-1-benzothiophene-2-carboxamide; D011758:Pyrroles; D013449:Sulfonamides; D050916:TRPV Cation Channels; C416986:TRPV4 protein, human; D007930:Leucine; D002118:Calcium
keywords: CELL VOLUME REGULATION; HUMAN MÜLLER CELLS; INTRACELLULAR CALCIUM LEVELS; MEMBRANE POTENTIAL; TRPV4