Release of taurine and glutamate contributes to cell volume regulation in human retinal Müller cells: Differences in modulation by calcium
Por:
Netti V., Pizzoni A., Pérez-Domínguez M., Ford P., Pasantes-Morales H., Ramos-Mandujano G., Capurro C.
Publicada:
1 sep 2018
Resumen:
Neuronal activity in the retina generates osmotic gradients that lead to Müller cell swelling, followed by a regulatory volume decrease (RVD) response, partially due to the isoosmotic efflux of KCl and water. However, our previous studies in a human Müller cell line (MIO-M1) demonstrated that an important fraction of RVD may also involve the efflux of organic solutes. We also showed that RVD depends on the swelling-induced Ca2+ release from intracellular stores. Here we investigate the contribution of taurine (Tau) and glutamate (Glu), the most relevant amino acids in Müller cells, to RVD through the volume-regulated anion channel (VRAC), as well as their Ca2+ dependency in MIO-M1 cells. Swelling-induced [3H]Tau/ [3H]Glu release was assessed by radiotracer assays and cell volume by fluorescence videomicroscopy. Results showed that cells exhibited an osmosensitive efflux of [3H]Tau and [3H]Glu (Tau > Glu) blunted by VRAC inhibitors 4-(2-butyl-6,7-dichloro-2-cyclopentylindan-1-on-5-yl)-oxybutyric acid and carbenoxolone reducing RVD. Only [3H]Tau efflux was mainly dependent on Ca2+ release from intracellular stores. RVD was unaffected in a Ca2+-free medium, probably due to Ca2+-independent Tau and Glu release, but was reduced by chelating intracellular Ca2+. The inhibition of phosphatidylinositol-3-kinase reduced [3H]Glu efflux but also the Ca2+-insensitive [3H]Tau fraction and decreased RVD, providing evidence of the relevance of this Ca2+-independent pathway. We propose that VRAC-mediated Tau and Glu release has a relevant role in RVD in Müller cells. The observed disparities in Ca2+ influence on amino acid release suggest the presence of VRAC isoforms that may differ in substrate selectivity and regulatory mechanisms, with important implications for retinal physiology. NEW & NOTEWORTHY The mechanisms for cell volume regulation in retinal Müller cells are still unknown. We show that swelling-induced taurine and glutamate release mediated by the volume-regulated anion channel (VRAC) largely contributes the to the regu- latory volume decrease response in a human Müller cell line. Interestingly, the hypotonic-induced efflux of these amino acids exhibits disparities in Ca2+-dependent and-independent regulatory mechanisms, which strongly suggests that Müller cells may express different VRAC heteromers formed by the recently discovered leu-cine-rich repeat containing 8 (LRRC8) proteins. © 2018 American Physiological Society. All rights reserved.
Filiaciones:
Netti V.:
Universidad de Buenos Aires, Facultad de Medicina, Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Buenos Aires, Argentina
CONICET-Universidad de Buenos Aires, Instituto de Fisiología y Biofísica “Bernardo Houssay”, Buenos Aires, Argentina
Pizzoni A.:
Universidad de Buenos Aires, Facultad de Medicina, Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Buenos Aires, Argentina
CONICET-Universidad de Buenos Aires, Instituto de Fisiología y Biofísica “Bernardo Houssay”, Buenos Aires, Argentina
Pérez-Domínguez M.:
Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
Ford P.:
Universidad de Buenos Aires, Facultad de Medicina, Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Buenos Aires, Argentina
CONICET-Universidad de Buenos Aires, Instituto de Fisiología y Biofísica “Bernardo Houssay”, Buenos Aires, Argentina
Pasantes-Morales H.:
División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
Ramos-Mandujano G.:
División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
Capurro C.:
Universidad de Buenos Aires, Facultad de Medicina, Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Buenos Aires, Argentina
CONICET-Universidad de Buenos Aires, Instituto de Fisiología y Biofísica “Bernardo Houssay”, Buenos Aires, Argentina
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