title: Modulation of Kv4.2 K+ currents by neuronal interleukin-16, a PDZ domain-containing protein expressed in the hippocampus and cerebellum.
abstract: Neuronal interleukin-16 (NIL-16) is a multi-PDZ domain protein expressed in post-mitotic neurons of the hippocampus and cerebellum. NIL-16 contains four PDZ domains, two of which are located within the neuron-specific N-terminal region. In yeast two-hybrid systems, the N-terminus of NIL-16 interacts with several ion channel proteins, including the Kv4.2 subunit of A-type K(+) channels. Here we provide evidence that NIL-16, through interactions with Kv4.2, influences Kv4.2 channel function and subcellular distribution. Specifically, coexpression of NIL-16 with Kv4.2 in COS-7 cells results in a significant reduction in whole-cell A-type current densities; however, when the Kv4.2 PDZ-ligand domain is mutated, Kv4.2 current densities are not affected by NIL-16 coexpression. Moreover, single-channel conductance was not influenced by the presence of NIL-16. In hippocampal neurons, A-type current densities are increased by conditions that inhibit interactions between NIL-16 and Kv4.2, such as overexpression of the Kv4.2 C-terminal PDZ-ligand domain and treatment with small-interfering RNA duplexes that reduce NIL-16 expression. Results of surface biotinylation assays using COS-7 cells suggest that Kv4.2 surface expression levels are reduced by coexpression with NIL-16. In addition, coexpression of NIL-16 with Kv4.2 induces Kv4.2 to form dense intracellular clusters; whereas without NIL-16, Kv4.2 channels cells are dispersed. Taken together, these data suggest that interactions between Kv4.2 and NIL-16 may reduce the number of functional Kv4.2-containing channels on the cell surface. In summary, NIL-16 may provide a novel form of A-type K(+) channel modulation that is localized specifically to neurons of the hippocampus and cerebellum.
authors.affiliation: Department of Biology, Rhodes College, Memphis, TN 38112, USA. cfenster@wooster.edu
authors.forename: Catherine P
authors.initials: CP
authors.lastname: Fenster
authors.forename: Steven D
authors.initials: SD
authors.lastname: Fenster
authors.forename: Hannah P
authors.initials: HP
authors.lastname: Leahy
authors.forename: Cornelia
authors.initials: C
authors.lastname: Kurschner
authors.forename: Jay A
authors.initials: JA
authors.lastname: Blundon
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D019921:Biotinylation / Q000379:methods; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism*; D002522:Chlorocebus aethiops; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D019410:Interleukin-16 / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D016296:Mutagenesis / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D034741:RNA, Small Interfering / Q000494:pharmacology; D051672:Shal Potassium Channels / Q000502:physiology*; D014162:Transfection / Q000379:methods
chemical_list: D019410:Interleukin-16; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D051672:Shal Potassium Channels; C121432:neuronal interleukin-16; D049452:Green Fluorescent Proteins