title: A heteromeric potassium channel involved in the modulation of the plasma membrane potential is essential for the survival of African trypanosomes.
abstract: Discovery of novel drug targets may lead to improved treatment of trypanosomiasis. We characterize here 2 gene products of Trypanosoma brucei that are essential for the growth of bloodstream form (BSF) parasites, as shown by RNA interference (RNAi)-mediated down-regulation of the individual mRNAs. The primary sequences of the 2 proteins--protein encoded by gene Tb927.1.4450 (TbK1) and protein encoded by gene Tb927.9.4820 (TbK2)--indicate that both belong to the family of putative, Ca(2+)-activated potassium channels. The proteins were expressed in Xenopus laevis oocytes and their functions investigated by use of electrophysiological techniques. Only combined expression of TbK1 and TbK2 results in the formation of sizeable currents, indicating that these proteins probably assemble into a heteromeric ion channel. The current mediated by this channel shows little time and voltage dependence and displays a permeability ratio of K(+)/Na(+) of >20. The known potassium channel blocker barium inhibits this channel with a half-maximal inhibitory concentration (IC50) of 98 ± 15 μM. The membrane potential of trypanosomes was measured with a fluorescent dye. Individual RNAi-mediated down-regulation of TbK1 or TbK2 eliminates a potassium conductance in the plasma membrane of BSF. Thus, this heteromeric potassium channel is involved in the modulation of the plasma membrane potential and represents a novel drug target in T. brucei.
authors: *Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland; Swiss Tropical and Public Health Institute, Basel, Switzerland; and University of Basel, Basel, Switzerland.
authors: Michael E
authors: ME
authors: Steinmann
authors: *Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland; Swiss Tropical and Public Health Institute, Basel, Switzerland; and University of Basel, Basel, Switzerland.
authors: Amaia
authors: A
authors: González-Salgado
authors: *Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland; Swiss Tropical and Public Health Institute, Basel, Switzerland; and University of Basel, Basel, Switzerland.
authors: Peter
authors: P
authors: Bütikofer
authors: *Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland; Swiss Tropical and Public Health Institute, Basel, Switzerland; and University of Basel, Basel, Switzerland.
authors: Pascal
authors: P
authors: Mäser
authors: *Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland; Swiss Tropical and Public Health Institute, Basel, Switzerland; and University of Basel, Basel, Switzerland sigel@ibmm.unibe.ch.
authors: Erwin
authors: E
authors: Sigel
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000235:genetics*; D015536:Down-Regulation / Q000235:genetics; D008564:Membrane Potentials / Q000235:genetics*; D009865:Oocytes / Q000469:parasitology; D011188:Potassium / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry; D012964:Sodium / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000235:genetics*; D014982:Xenopus laevis / Q000235:genetics
chemical_list: D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger; D012964:Sodium; D017346:Protein Serine-Threonine Kinases; D011188:Potassium
keywords: Trypanosoma brucei; Xenopus laevis oocytes; electrophysiology