Identification by mass spectrometry and functional characterization of two phosphorylation sites of KCNQ2/KCNQ3 channels.
Neuronal potassium channel subunits of the KCNQ (Kv7) family underlie M-current (I(M)), and may also underlie the slow potassium current at the node of Ranvier, I(Ks). I(M) and I(Ks) are outwardly rectifying currents that regulate excitability of neurons and myelinated axons, respectively. Studies of native I(M) and heterologously expressed Kv7 subunits suggest that, in vivo, KCNQ channels exist within heterogeneous, multicomponent protein complexes. KCNQ channel properties are regulated by protein phosphorylation, protein-protein interactions, and protein-lipid interactions within such complexes. To better understand the regulation of neuronal KCNQ channels, we searched directly for posttranslational modifications on KCNQ2/KCNQ3 channels in vivo by using mass spectrometry. Here we describe two sites of phosphorylation. One site, specific for KCNQ3, appears functionally silent in electrophysiological assays but is located in a domain previously shown to be important for subunit tetramerization. Mutagenesis and electrophysiological studies of the second site, located in the S4-S5 intracellular loop of all KCNQ subunits, reveal a mechanism of channel inhibition.
Surti
Toral S
TS
Graduate Group in Biophysics, University of California, 1550 4th Street, Room 484, San Francisco, CA 94143-0725, USA.
Huang
Lan
L
Jan
Yuh Nung
YN
Jan
Lily Y
LY
Cooper
Edward C
EC
D000595:Amino Acid Sequence; D000818:Animals; D002846:Chromatography, Affinity; D004594:Electrophysiology; D006801:Humans; D051658:KCNQ2 Potassium Channel / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D051659:KCNQ3 Potassium Channel / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D010769:Phosphothreonine / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
D051658:KCNQ2 Potassium Channel; D051659:KCNQ3 Potassium Channel; D010769:Phosphothreonine