Functional coupling between the Kv1.1 channel and aldoketoreductase Kvbeta1.
The Shaker family voltage-dependent potassium channels (Kv1) assemble with cytosolic beta-subunits (Kvbeta) to form a stable complex. All Kvbeta subunits have a conserved core domain, which in one of them (Kvbeta2) is an aldoketoreductase that utilizes NADPH as a cofactor. In addition to this core, Kvbeta1 has an N terminus that closes the channel by the N-type inactivation mechanism. Point mutations in the putative catalytic site of Kvbeta1 alter the on-rate of inactivation. Whether the core of Kvbeta1 functions as an enzyme and whether its enzymatic activity affects N-type inactivation had not been explored. Here, we show that Kvbeta1 is a functional aldoketoreductase and that oxidation of the Kvbeta1-bound cofactor, either enzymatically by a substrate or non-enzymatically by hydrogen peroxide or NADP(+), induces a large increase in open channel current. The modulation is not affected by deletion of the distal C terminus of the channel, which has been suggested in structural studies to interact with Kvbeta. The rate of increase in current, which reflects NADPH oxidation, is approximately 2-fold faster at 0-mV membrane potential than at -100 mV. Thus, cofactor oxidation by Kvbeta1 is regulated by membrane potential, presumably via voltage-dependent structural changes in Kv1.1 channels.
Pan
Yaping
Y
Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
Weng
Jun
J
Cao
Yu
Y
Bhosle
Rahul C
RC
Zhou
Ming
M
D000449:Aldehyde Reductase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D004594:Electrophysiology; D004789:Enzyme Activation; D005260:Female; D017353:Gene Deletion; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015640:Ion Channel Gating; D009249:NADP / Q000378:metabolism; D009865:Oocytes; D010084:Oxidation-Reduction / Q000187:drug effects; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D051381:Rats; D051637:Shaker Superfamily of Potassium Channels / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D014982:Xenopus laevis
D051637:Shaker Superfamily of Potassium Channels; D009249:NADP; D006861:Hydrogen Peroxide; D000449:Aldehyde Reductase