title: Identification and functional characterization of EhClC-A, an Entamoeba histolytica ClC chloride channel located at plasma membrane.
abstract: ClC chloride channels perform a wide variety of physiological functions and they had been characterized in animals, yeast, plants and bacteria but not in protozoa. By blast search we found in Entamoeba histolytica, the protozoan responsible for human amoebiasis, two genes (Ehclc-A and Ehclc-B) encoding for putative polypeptides with 25-30% identity to ClC chloride channels of several organisms. Reverse transcription polymerase chain reaction (RT-PCR) experiments showed that both genes are transcribed in trophozoites. Phylogenetic analysis revealed that EhClC-A and EhClC-B polypeptides belong to the eukaryotic branch of plasma membrane ClCs. Specific antibodies against EhClC-A confirmed that it is located at the trophozoite plasma membrane. Xenopus laevis oocytes microinjected with Ehclc-A cRNA elicited anion currents not detected in oocytes microinjected with water. Induced currents were inwardly rectifying and had a permeability sequence of Cl->Br->I->F->>NO3-. The chloride channel blocker 4-acetamido-4'isothiocyanostilbene-2, 2'-disulphonic acid (SITS) strongly inhibited the oocytes anion currents and trophozoites growth. Experiments at diverse pHs suggested that EhClC-A is not a Cl-/H+ exchanger, but it is an ion channel that could be involved in pH regulation. EhClC-A may also participate in cell volume regulation. As far as we know, EhClC-A is the first chloride channel characterized in protozoa.
authors.affiliation: Department of Experimental Pathology, Centro de Investigacion y de Estudios Avanzados del IPN A.P. 14-740, Mexico D.F. 07000, Mexico.
authors.forename: Andrés
authors.initials: A
authors.lastname: Salas-Casas
authors.forename: Arturo
authors.initials: A
authors.lastname: Ponce-Balderas
authors.forename: Rosa María
authors.initials: RM
authors.lastname: García-Pérez
authors.forename: Pedro
authors.initials: P
authors.lastname: Cortés-Reynosa
authors.forename: Gerardo
authors.initials: G
authors.lastname: Gamba
authors.forename: Esther
authors.initials: E
authors.lastname: Orozco
authors.forename: Mario A
authors.initials: MA
authors.lastname: Rodríguez
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D003001:Cloning, Molecular; D004594:Electrophysiology; D004748:Entamoeba histolytica / Q000235:genetics / Q000502:physiology*; D017125:Genes, Protozoan; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D009865:Oocytes; D010802:Phylogeny; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014981:Xenopus
chemical_list: D018118:Chloride Channels; D008565:Membrane Proteins; D015800:Protozoan Proteins