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The Journal of Neuroscience, May 7, 2008, 28(19):4982-4994; doi:10.1523/JNEUROSCI.0186-08.2008

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Cellular/Molecular
Interdomain Cytoplasmic Interactions Govern the Intracellular Trafficking, Gating, and Modulation of the Kv2.1 Channel

Durga P. Mohapatra,¹ Dominic F. Siino,¹ and James S. Trimmer^1,2

¹Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, and ²Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, California 95616

Correspondence should be addressed to Dr. James S. Trimmer, Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, 196 Briggs Hall, University of California, One Shields Avenue, Davis, CA 95616-8519. Email: jtrimmer{at}ucdavis.edu

Voltage-gated potassium (Kv) channels comprise four transmembrane subunits, often associated with cytoplasmic β subunits that impact channel expression and function. Here, we show that cell surface expression, voltage-dependent activation gating, and phosphorylation-dependent modulation of Kv2.1 are regulated by cytoplasmic N/C interaction within the subunit. Kv2.1 surface expression is greatly reduced by C-terminal truncation. Tailless Kv2.1 channels exhibit altered voltage-dependent gating properties and lack the bulk of the phosphorylation-dependent modulation of channel gating. Remarkably, the soluble C terminus of Kv2.1 associates with tailless channels and rescues their expression, function, and phosphorylation-dependent modulation. Soluble N and C termini of Kv2.1 can also interact directly. We also show that the N/C-terminal interaction in Kv2.1 is governed by a 34 aa motif in the juxtamembrane cytoplasmic C terminus, and a 17 aa motif located in the N terminus at a position equivalent to the β subunit binding site in other Kv channels. Deletion of either motif disrupts N/C-terminal interaction and surface expression, function, and phosphorylation-dependent modulation of Kv2.1 channels. These findings provide novel insights into intrinsic mechanisms for the regulation of Kv2.1 trafficking, gating, and phosphorylation-dependent modulation through cytoplasmic N/C-terminal interaction, which resembles /β subunit interaction in other Kv channels.

Key words: hippocampal neurons; potassium channel; assembly; immunocytochemistry; electrophysiology; phosphorylation

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Received Jan. 15, 2008; revised March 28, 2008; accepted March 31, 2008.

Correspondence should be addressed to Dr. James S. Trimmer, Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, 196 Briggs Hall, University of California, One Shields Avenue, Davis, CA 95616-8519. Email: jtrimmer{at}ucdavis.edu

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