INFLUENCE OF DETERGENTS ON THE FUNCTION OF CLONED POTASSIUM CHANNELS

The influence of detergents on cloned potassium channels expressed in Xenopus oocytes was investigated. Bath application of Triton X-100 cau sed a dose-dependent reduction of the peak current through the delayed rectifier channel rKv2.1 and a fast, time-and voltage-dependent, curr ent inactivation. Onset of inactivation was observed at concentrations as low as 1 mu M; at 100 mu M inactivation proceeded with a time cons tant of about 50 ms at +50 mV. The effect of Triton did not compete wi th extracellular TEA and the tail current kinetics was accelerated, in dicating that the molecular mechanism is not a simple open-channel blo ck. In patch-clamp recordings the effects were readily reversible and application of detergents from the inside were most effective. Triton induced similar effects in hKv1.5 channels; for rKv1.1, d-eag, and Kir 2.1 mainly a current reduction was observed. No effect of 100 mu M Tri ton was found for the plant inward rectifier channel KAT1. Investigati on of Shaker channel mutants revealed a dependence of the Triton effec t upon the degree and nature of C-type inactivation. Only detergents w ith a long hydrophobic carbohydrate chain and a hydrophilic chain of t he polyethyleneglycol type caused inactivation of rKv2.1 (e.g., Triton X-100, Thesit, Brij35 were active; CHAPS and MEGA-8 were inactive). T he presented data reveal that there are channel-and detergent-specific interactions which can result in fast inactivation leading to physiol ogical effects similar to those exerted by local anesthetics and antia rrhythmic agents.