title: The molecular and functional interaction between ICln and HSPC038 proteins modulates the regulation of cell volume.
abstract: Identifying functional partners for protein/protein interactions can be a difficult challenge. We proposed the use of the operon structure of the Caenorhabditis elegans genome as a "new gene-finding tool" (Eichmüller, S., Vezzoli, V., Bazzini, C., Ritter, M., Fürst, J., Jakab, M., Ravasio, A., Chwatal, S., Dossena, S., Bottà, G., Meyer, G., Maier, B., Valenti, G., Lang, F., and Paulmichl, M. (2004) J. Biol. Chem. 279, 7136-7146) that could be functionally translated to the human system. Here we show the validity of this approach by studying the predicted functional interaction between ICln and HSPC038. In C. elegans, the gene encoding for the ICln homolog (icln-1) is embedded in an operon with two other genes, Nx (the human homolog of Nx is HSPC038) and Ny. ICln is a highly conserved, ubiquitously expressed multifunctional protein that plays a critical role in the regulatory volume decrease after cell swelling. Following hypotonic stress, ICln translocates from the cytosol to the plasma membrane, where it has been proposed to participate in the activation of the swelling-induced chloride current (ICl(swell)). Here we show that the interaction between human ICln and HSPC038 plays a role in volume regulation after cell swelling and that HSPC038 acts as an escort, directing ICln to the cell membrane after cell swelling and facilitating the activation of ICl(swell). Assessment of the NMR structure of HSPC038 showed the presence of a zinc finger motif. Moreover, NMR and additional biochemical techniques enabled us to identify the putative ICln/HSPC038 interacting sites, thereby explaining the functional interaction of both proteins on a molecular level.
authors.affiliation: Institute of Pharmacology and Toxicology, Paracelsus Medical University, A-5020 Salzburg, Austria. silvia.dossena@pmu.ac.at
authors.forename: Silvia
authors.initials: S
authors.lastname: Dossena
authors.forename: Rosaria
authors.initials: R
authors.lastname: Gandini
authors.forename: Grazia
authors.initials: G
authors.lastname: Tamma
authors.forename: Valeria
authors.initials: V
authors.lastname: Vezzoli
authors.forename: Charity
authors.initials: C
authors.lastname: Nofziger
authors.forename: Margherita
authors.initials: M
authors.lastname: Tamplenizza
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Salvioni
authors.forename: Emanuele
authors.initials: E
authors.lastname: Bernardinelli
authors.forename: Giuliano
authors.initials: G
authors.lastname: Meyer
authors.forename: Giovanna
authors.initials: G
authors.lastname: Valenti
authors.forename: Magnus
authors.initials: M
authors.lastname: Wolf-Watz
authors.forename: Johannes
authors.initials: J
authors.lastname: Fürst
authors.forename: Markus
authors.initials: M
authors.lastname: Paulmichl
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D048429:Cell Size; D002712:Chlorides / Q000378:metabolism; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006801:Humans; D007473:Ion Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009997:Osmotic Pressure; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D021381:Protein Transport; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C410035:CLNS1A protein, human; D002712:Chlorides; D007473:Ion Channels; D011506:Proteins; C569295:ZNF706 protein, human