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Olaf Strauss, Nadine Reichhart, Susanne Keckeis; Ano2 contributes to the outwardly rectifying Ca2+-dependent Cl- conductance in the retinal pigment epithelium. Invest. Ophthalmol. Vis. Sci. 2016;57(12):261.
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© ARVO (1962-2015); The Authors (2016-present)
The retinal pigment epithelium (RPE) expresses a variety of Cl channels which contribute to transepithelial transport of Cl- and water. The Ca2+-dependent Cl channel in the RPE can adopt the transepithelial transport to the functional needs by rises of intracellular free Ca2+ as second messenger. Patch-clamp data from different groups have described the Ca2+-dependent Cl channel in the RPE as an outwardly rectifying channel which shows properties of anoctamin-2 (Ano2), a member of a Ca2+-dependent ion channel family. The purpose of the study is to characterize the molecular identity of the Ca2+-dependent Cl channel in the RPE.
Analysis of the expression pattern of Ano2 in the mouse retina and human ARPE-19 cell line; patch-clamp analysis of ATP-induced Cl- conductance in ARPE-19 cells; siRNA approach against Ano2.
In sagittal sections of the mouse retina, we found Ano2 in the basolateral membrane of the RPE. ARPE-19 cells showed Ano2 expression at the mRNA and the protein level. Stimulation of ARPE-19 cells with 500µM ATP, which leads to a transient increase in intracellular free Ca2+, transiently stimulated an outwardly rectifying Cl- conductance which showed reversal potentials close the Cl- equilibrium potential and was blocked by DIDS and niflumic acid. siRNA knock-down of Ano2 in ARPE-19 cells reduced the Ano2 protein and Ca2+-dependent Cl- conductance.
Ano2 contributes to the basolateral Ca2+-dependent Cl – conductance in the RPE. Its biophysical properties correspond with that of previous publications. Thus Ano2 is a major Ca2+-dependent Cl channel in the RPE.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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