Regulation of the voltage-gated K(+) channels KCNQ2/3 and KCNQ3/5 by ubiquitination. Novel role for Nedd4-2.

School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia.
The muscarine-sensitive K(+) current (M-current) stabilizes the resting membrane potential in neurons, thus limiting neuronal excitability. The M-current is mediated by heteromeric channels consisting of KCNQ3 subunits in association with either KCNQ2 or KCNQ5 subunits. The role of KCNQ2/3/5 in the regulation of neuronal excitability is well established; however, little is known about the mechanisms that regulate the cell surface expression of these channels. Ubiquitination by the Nedd4/Nedd4-2 ubiquitin ligases is known to regulate a number of membrane ion channels and transporters. In this study, we investigated whether Nedd4/Nedd4-2 could regulate KCNQ2/3/5 channels. We found that the amplitude of the K(+) currents mediated by KCNQ2/3 and KCNQ3/5 were reduced by Nedd4-2 (but not Nedd4) in a Xenopus oocyte expression system. Deletion experiments showed that the C-terminal region of the KCNQ3 subunit is required for the Nedd4-2-mediated regulation of the heteromeric channels. Glutathione S-transferase fusion pulldowns and co-immunoprecipitations demonstrated a direct interaction between KCNQ2/3 and Nedd4-2. Furthermore, Nedd4-2 could ubiquitinate KCNQ2/3 in transfected cells. Taken together, these data suggest that Nedd4-2 is potentially an important regulator of M-current activity in the nervous system.
Mesh Terms:
Amino Acid Motifs, Animals, Down-Regulation, Endosomal Sorting Complexes Required for Transport, Gene Expression Regulation, Humans, KCNQ Potassium Channels, KCNQ2 Potassium Channel, KCNQ3 Potassium Channel, Membrane Potentials, Oocytes, Protein Binding, Rats, Ubiquitin, Ubiquitin-Protein Ligases, Xenopus laevis
J. Biol. Chem. Apr. 20, 2007; 282(16);12135-42 [PUBMED:17322297]
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