Intracellular K + concentration decrease is not obligatory for apoptosis

Abstract

K + efflux is observed as an early event in the apoptotic process in various cell types. Loss of intracellular K + and subsequent reduction in ionic strength are suggested to release the inhibition of proapoptotic caspases. In this work, a new K +-specific microelectrode was used to study possible alterations in intra-cellular K + in Xenopus laevis oocytes during chemically induced apoptosis. The accuracy of the microelectrode to detect changes in intracellular K + was verified with parallel electrophysiological measurements. In concordance with previous studies on other cell types, apoptotic stimuli reduced the intracellular K +concentration in Xenopus oocytes and increased caspase-3 activity. The reduction in intracellular K + was prevented by dense expression of voltage-gated K (Kv) channels. Despite this, the caspase-3 activity was increased similarly in Kv channelexpressing oocytes as in oocytes not expressing Kv channels. Thus, in Xenopus oocytes caspase-3 activity is not dependent on the intracellular concentration of K +. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.