ICln ion channel splice variants in Caenorhabditis elegans: Voltage dependence and interaction with an operon partner protein Journal Article

Author(s): Fürst, Johannes; Ritter, Markus; Rudzki, Jakob; Danzl, Johannes G; Gschwentner, Martin; Scandella, Elke; Jakab, Martin; König, Matthias A; Oehl, Bernhard; Lang, Florian; Deetjen, Peter; Paulmichl, Markus
Article Title: ICln ion channel splice variants in Caenorhabditis elegans: Voltage dependence and interaction with an operon partner protein
Abstract: ICln is an ion channel identified by expression cloning using a cDNA library from Madin-Darby canine kidney cells. In all organisms tested so far, only one transcript for the ICln protein could be identified. Here we show that two splice variants of the ICln ion channel can be found in Caenorhabditis elegans. Moreover, we show that these two splice variants of the ICln channel protein, which we termed IClnN1 and IClnN2, can be functionally reconstituted and tested in an artificial lipid bilayer. In these experiments, the IClnN1-induced currents showed no voltage-dependent inactivation, whereas the IClnN2-induced currents fully inactivated at positive potentials. The molecular entity responsible for the voltage-dependent inactivation of IClnN2 is a cluster of positively charged amino acids encoded by exon 2a, which is absent in IClnN1. Our experiments suggest a mechanism of channel inactivation that is similar to the "ball and chain" model proposed for the Shaker potassium channel, i.e. a cluster of positively charged amino acids hinders ion permeation through the channel by a molecular and voltage-dependent interaction at the inner vestibulum of the pore. This hypothesis is supported by the finding that synthetic peptides with the same amino acid sequence as the positive cluster can transform the IClnN1-induced current to the current observed after reconstitution of IClnN2. Furthermore, we show that the nematode ICln gene is embedded in an operon harboring two additional genes, which we termed Nx and Ny. Co-reconstitution of Nx and IClnN2 and functional analysis of the related currents revealed a functional interaction between the two proteins, as evidenced by the fact that the IClnN2-induced current in the presence of Nx was no longer voltage-sensitive. The experiments described indicate that the genome organization in nematodes allows an effective approach for the identification of functional partner proteins of ion channels.
Journal Title: Journal of Biological Chemistry
Volume: 277
Issue 6
ISSN: 1083-351X
Publisher: American Society for Biochemistry and Molecular Biology  
Date Published: 2002-02-08
Start Page: 4435
End Page: 4445
DOI: 10.1074/jbc.M107372200
Notes: This work was supported in part by Austrian Science Foundation Grants P12337, P13041, P12467 and P14102; Austrian National Bank Grants 8444 and 6994; Gastein Foundation Grant FP41/FP46; and European Commission Grant BMH4-CT96-0602 (to M. P. and M. R.). TheCaenorhabditis Genetics Center (which supplied the N2 strain) is supported by the National Institutes of Health National Center for Research Resources.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Open access: no