title: Hsp90 is involved in the regulation of cytosolic precursor protein abundance in tomato.
abstract: Cytosolic chaperones are involved in the regulation of cellular protein homeostasis in general. Members of the families of heat stress proteins 70 (Hsp70) and 90 (Hsp90) assist the transport of preproteins to organelles such as chloroplasts or mitochondria. In addition, Hsp70 was described to be involved in the degradation of chloroplast preproteins that accumulate in the cytosol. Because a similar function has not been established for Hsp90, we analyzed the influences of Hsp90 and Hsp70 on the protein abundance in the cellular context using an in vivo system based on mesophyll protoplasts. We observed a differential behavior of preproteins with respect to the cytosolic chaperone-dependent regulation. Some preproteins such as pOE33 show a high dependence on Hsp90, whereas the abundance of preproteins such as pSSU is more strongly dependent on Hsp70. The E3 ligase, C-terminus of Hsp70-interacting protein (Chip), appears to have a more general role in the control of cytosolic protein abundance. We discuss why the different reaction modes are comparable with the cytosolic unfolded protein response.
authors.affiliation: Department of Molecular Cell Biology of Plants, Goethe-University, Max-von-Laue Street 9, 60438 Frankfurt am Main, Germany.
authors.forename: Bodo
authors.initials: B
authors.lastname: Tillmann
authors.affiliation: Department of Molecular Cell Biology of Plants, Goethe-University, Max-von-Laue Street 9, 60438 Frankfurt am Main, Germany.
authors.forename: Sascha
authors.initials: S
authors.lastname: Röth
authors.affiliation: Department of Molecular Cell Biology of Plants, Goethe-University, Max-von-Laue Street 9, 60438 Frankfurt am Main, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Bublak
authors.affiliation: Department of Molecular Cell Biology of Plants, Goethe-University, Max-von-Laue Street 9, 60438 Frankfurt am Main, Germany; Buchman Institute for Molecular Life Sciences, Goethe University, Max-von-Laue Street 15, 60438 Frankfurt am Main, Germany; Institute of Cell Biology, Goethe-Universität, Max-von-Laue Straße 9, 60438 Frankfurt am Main, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Sommer
authors.affiliation: Cluster of Excellence 'Macromolecular Complexes', Goethe-University, 60438 Frankfurt am Main, Germany; Center of Membrane Proteomics, Goethe University, Max-von-Laue Street 9, 60438 Frankfurt am Main, Germany; Buchman Institute for Molecular Life Sciences, Goethe University, Max-von-Laue Street 15, 60438 Frankfurt am Main, Germany; Institute of Cell Biology, Goethe-Universität, Max-von-Laue Straße 9, 60438 Frankfurt am Main, Germany.
authors.forename: Ernst H K
authors.initials: EH
authors.lastname: Stelzer
authors.affiliation: Department of Molecular Cell Biology of Plants, Goethe-University, Max-von-Laue Street 9, 60438 Frankfurt am Main, Germany.
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Scharf
authors.affiliation: Department of Molecular Cell Biology of Plants, Goethe-University, Max-von-Laue Street 9, 60438 Frankfurt am Main, Germany; Cluster of Excellence 'Macromolecular Complexes', Goethe-University, 60438 Frankfurt am Main, Germany; Center of Membrane Proteomics, Goethe University, Max-von-Laue Street 9, 60438 Frankfurt am Main, Germany; Buchman Institute for Molecular Life Sciences, Goethe University, Max-von-Laue Street 15, 60438 Frankfurt am Main, Germany. Electronic address: schleiff@bio.uni-frankfurt.de.
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D003600:Cytosol / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000378:metabolism*; D056811:Unfolded Protein Response / Q000502:physiology
chemical_list: D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins
keywords: CPR; Hsp70; Hsp90; chip; cytosolic unfolded protein response; preprotein degradation