Electrophysiological characterization of potassium conductive pathways in Trypanosoma cruzi

Abstract

Potassium channels (K(+) channels) are members of one of the largest and most diverse families of membrane proteins, widely described from bacteria to humans. Their functions include voltage-membrane potential maintenance, pH and cell volume regulation, excitability, organogenesis and cell death. K(+) channels are involved in sensing and responding to environmental changes such as acidification, O(2) pressure, osmolarity, and ionic concentration. Trypanosoma cruzi is a parasitic protozoan, causative agent of Chagas disease (American trypanosomiasis) an endemic pathology in Latin America, where up 200,000 new cases are reported annually. In protozoan parasites, the presence of K(+) channels has been suggested, but functional direct evidence supporting this hypothesis is limited, mainly due to the difficulty of employing conventional electrophysiological methods to intact parasites. In T. cruzi, K(+) conductive pathways are thought to contribute in the regulatory volume decrease observed under hypoosmotic stress, the steady state pH and the compensatory response to extracellular acidification and the maintenance of plasma membrane potential. In this work we describe the isolation of plasma membrane enriched fractions from T. cruzi epimastigotes, their reconstitution into giant liposomes and the first functional characterization by patch-clamp of K(+) conductive pathways in protozoan parasites.