Pendrin overexpression affects cell volume recovery, intracellular pH and chloride concentration after hypotonicity-induced cell swelling.

[pendred syndrome]

The pendrin (SLC 26 A 4 or PDS ) gene is responsible , when mutated , for the Pendred syndrome , a recessive disorder characterized by sensorineural hearing loss often accompanied by thyroid dysfunctions . Pendrin protein is an anion exchanger and we focused on a still unexplored function that it might play in view of its importance in the inner ear : Cl (-) fluxes regulation during cellular volume control . We challenged HEK-293 Phoenix cells over-expressing wild type pendrin (PDS HEK cells ) together with the EYFP (Enhanced Yellow Fluorescent Protein ) or over-expressing the EYFP alone (control HEK cells ) with hypo-osmolar solutions . Taking advantage of the confocal optical sectioning we measured the cell volume . In addition , we determined the intracellular pH and chloride concentration with fluorescent probes (EYFP and seminaphthorhodafluor-5 F , SNARF-5 F ). Consequently , we could estimate simultaneously Cl (-) fluxes , cellular volume and intracellular pH variations . Cl (-) movements markedly differed between PDS and control HEK cells upon hypotonic shock and are accompanied by an attenuation of the swelling induced pH drop in PDS HEK cells . The contemporary measurements of the three variables not yet reported in living cells , allowed to assess a possible influence of pendrin upregulation in volume homeostasis and evidenced its participation to Cl (-) fluxes .