title: Peroxisomal Pex11 is a pore-forming protein homologous to TRPM channels.
abstract: More than 30 proteins (Pex proteins) are known to participate in the biogenesis of peroxisomes-ubiquitous oxidative organelles involved in lipid and ROS metabolism. The Pex11 family of homologous proteins is responsible for division and proliferation of peroxisomes. We show that yeast Pex11 is a pore-forming protein sharing sequence similarity with TRPM cation-selective channels. The Pex11 channel with a conductance of Λ=4.1 nS in 1.0M KCl is moderately cation-selective (PK(+)/PCl(-)=1.85) and resistant to voltage-dependent closing. The estimated size of the channel's pore (r~0.6 nm) supports the notion that Pex11 conducts solutes with molecular mass below 300-400 Da. We localized the channel's selectivity determining sequence. Overexpression of Pex11 resulted in acceleration of fatty acids β-oxidation in intact cells but not in the corresponding lysates. The β-oxidation was affected in cells by expression of the Pex11 protein carrying point mutations in the selectivity determining sequence. These data suggest that the Pex11-dependent transmembrane traffic of metabolites may be a rate-limiting step in the β-oxidation of fatty acids. This conclusion was corroborated by analysis of the rate of β-oxidation in yeast strains expressing Pex11 with mutations mimicking constitutively phosphorylated (S165D, S167D) or unphosphorylated (S165A, S167A) protein. The results suggest that phosphorylation of Pex11 is a mechanism that can control the peroxisomal β-oxidation rate. Our results disclose an unexpected function of Pex11 as a non-selective channel responsible for transfer of metabolites across peroxisomal membrane. The data indicate that peroxins may be involved in peroxisomal metabolic processes in addition to their role in peroxisome biogenesis.
authors.affiliation: Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Ruhr-Universität, Bochum, Germany.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Mindthoff
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, Oulu, Finland.
authors.forename: Silke
authors.initials: S
authors.lastname: Grunau
authors.affiliation: Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Ruhr-Universität, Bochum, Germany.
authors.forename: Laura L
authors.initials: LL
authors.lastname: Steinfort
authors.affiliation: Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Ruhr-Universität, Bochum, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Girzalsky
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, Oulu, Finland.
authors.forename: J Kalervo
authors.initials: JK
authors.lastname: Hiltunen
authors.affiliation: Institut für Biochemie und Pathobiochemie, Abt. Systembiochemie, Ruhr-Universität, Bochum, Germany. Electronic address: ralf.erdmann@rub.de.
authors.forename: Ralf
authors.initials: R
authors.lastname: Erdmann
authors.affiliation: Faculty of Biochemistry and Molecular Medicine and Biocenter Oulu, University of Oulu, Oulu, Finland. Electronic address: vasily.antonenkov@oulu.fi.
authors.forename: Vasily D
authors.initials: VD
authors.lastname: Antonenkov
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D002942:Circular Dichroism; D005227:Fatty Acids / Q000378:metabolism; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010084:Oxidation-Reduction; D000074401:Peroxins; D020675:Peroxisomes / Q000378:metabolism*; D010766:Phosphorylation; D018272:Porins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D050053:TRPM Cation Channels / Q000235:genetics / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D008565:Membrane Proteins; C092128:PEX11 protein, S cerevisiae; D000074401:Peroxins; D018272:Porins; D029701:Saccharomyces cerevisiae Proteins; D050053:TRPM Cation Channels
keywords: Membrane channels; Peroxisomes; Protein phosphorylation; TRP channels; β-Oxidation