Penetratin Peptide Potentiates Endogenous Calcium-Activated Chloride Currents in Xenopus oocytes

Penetratin Peptide Potentiates Endogenous Calcium-Activated Chloride Currents in Xenopus oocytes Calcium-activated chloride currents (CaCCs) are required for epithelial electrolyte and fluid secretion, fertilization, sensory transduction and excitability of neurons and smooth muscle. Defolliculated Xenopus oocytes express a robust CaCC formed by a heterologous group of proteins including transmembrane protein 16A (TMEM16A) and bestrophins. Penetratin, a 17-amino acid peptide, potentiated endogenous oocyte CaCCs by ~50-fold at 10 μM, recorded using a two-electrode voltage clamp. CaCC potentiation was rapid and dose-dependent (EC50 = 3.2 μM). Penetratin-potentiated currents reversed at −18 mV and were dependent on the extracellular divalent cations present, showing positive regulation by Ca2+ and Mg2+ but effective block by Zn2+ (IC50 = 5.9 μM). Extracellular Cd2+, Cu2+ and Ba2+ resulted in bimodal responses: CaCC inhibition at low but potentiation at high concentrations. Intracellular BAPTA injection, which prevents activation of CaCCs, and the Cl− channel blockers niflumic acid and DIDS significantly reduced potentiation. In contrast, the K+ channel blockers Cs+, TEA, tertiapin-Q and halothane had no significant effect. This pharmacological profile is consistent with penetratin potentiation of zinc-sensitive CaCCs that are activated by influx of extracellular Ca2+. These findings may stimulate basic research on CaCCs in native cells and may lead to development of novel therapeutics targeting disorders caused by insufficient chloride secretion. The Journal of Membrane Biology Springer Journals

Penetratin Peptide Potentiates Endogenous Calcium-Activated Chloride Currents in Xenopus oocytes

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Copyright © 2011 by Springer Science+Business Media, LLC
Life Sciences; Biochemistry, general; Human Physiology
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