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The Journal of Neuroscience, November 22, 2006, 26(47):12137-12142; doi:10.1523/JNEUROSCI.2783-06.2006
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Brief Communications
Unanticipated Region- and Cell-Specific Downregulation of Individual KChIP Auxiliary Subunit Isotypes in Kv4.2 Knock-Out Mouse Brain
Milena Menegola and
James S. Trimmer
Department of Pharmacology, School of Medicine, University of California, Davis, California 95616
Correspondence should be addressed to Dr. James S. Trimmer, Department of Pharmacology, School of Medicine, 3502 Genomic and Biomedical Sciences Facility, University of California, One Shields Avenue, Davis, CA 95616. Email: jtrimmer{at}ucdavis.edu
Kv4 family voltage-gated potassium channel subunits and Kv channel-interacting protein (KChIP) and dipeptidyl aminopeptidase-like protein subunits comprise somatodendritic A-type channels in mammalian neurons. Recently, a mouse was generated with a targeted deletion of Kv4.2, a Kv4 subunit expressed in many but not all mammalian brain neurons. Kv4.2/ mice are grossly indistinguishable from wild-type (WT) littermates. Here we used immunohistochemistry to analyze expression of component Kv4 and KChIP subunits of A-type channels in WT and Kv4.2/ brains. We found that the expression level, and cellular and subcellular distribution of the other prominent brain Kv4 family member Kv4.3, was indistinguishable between WT and Kv4.2/ samples. However, we found unanticipated regional and cell-specific decreases in expression of KChIPs. The degree of altered expression of individual KChIP isoforms in different regions and neurons precisely follows the level of Kv4.2 normally found at those sites and presumably their extent of association of these KChIPs with Kv4.2. The dramatic effects of Kv4.2 deletion on KChIP expression suggest that, in addition to previously characterized effects of KChIPs on the functional properties, trafficking, and turnover rate of Kv4 channels, Kv4:KChIP association may confer reciprocal Kv4.2-dependent effects on KChIPs. The impact of Kv4.2 deletion on KChIP expression also supports the major role of KChIPs as auxiliary subunits of Kv4 channels.
Key words: cerebellum; dendrite; excitability; hippocampus; immunohistochemistry; ion channel
Received June 29, 2006;
revised Oct. 11, 2006;
accepted Oct. 13, 2006.
Correspondence should be addressed to Dr. James S. Trimmer, Department of Pharmacology, School of Medicine, 3502 Genomic and Biomedical Sciences Facility, University of California, One Shields Avenue, Davis, CA 95616. Email: jtrimmer{at}ucdavis.edu
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