title: Penetratin peptide potentiates endogenous calcium-activated chloride currents in Xenopus oocytes.
abstract: 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.
authors: School of Biomedical Sciences, University of Queensland, Brisbane, QLD, 4072, Australia, r.kanjhan@uq.edu.au.
authors: Refik
authors: R
authors: Kanjhan
authors: Mark C
authors: MC
authors: Bellingham
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002352:Carrier Proteins / Q000494:pharmacology*; D057846:Cell-Penetrating Peptides; D018118:Chloride Channels / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D014982:Xenopus laevis; D015032:Zinc / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D057846:Cell-Penetrating Peptides; D018118:Chloride Channels; D002712:Chlorides; C414409:penetratin; D008274:Magnesium; D015032:Zinc; D002118:Calcium