Peroxisomal Import Reduces the Proapoptotic Activity of Deubiquitinating Enzyme USP2.
The human deubiquitinating enzyme ubiquitin-specific protease 2 (USP2) regulates multiple cellular pathways, including cell proliferation and apoptosis. As a result of alternative splicing four USP2 isoenzymes are expressed in human cells of which all contain a weak peroxisome targeting signal of type 1 (PTS1) at their C-termini. Here, we systematically analyzed apoptotic effects induced by overexpression and intracellular localization for each isoform. All isoforms exhibit proapoptotic activity and are post-translationally imported into the matrix of peroxisomes in a PEX5-dependent manner. However, a significant fraction of the USP2 pool resides in the cytosol due to a weaker PTS1 and thus low affinity to the PTS receptor PEX5. Blocking of peroxisomal import did not interfere with the proapoptotic activity of USP2, suggesting that the enzyme performs its critical function outside of this compartment. Instead, increase of the efficiency of USP2 import into peroxisomes either by optimization of its peroxisomal targeting signal or by overexpression of the PTS1 receptor did result in a reduction of the apoptotic rate of transfected cells. Our studies suggest that peroxisomal import of USP2 provides additional control over the proapoptotic activity of cytosolic USP2 by spatial separation of the deubiquitinating enzymes from their interaction partners in the cytosol and nucleus.
Institut für Biochemie und Pathobiochemie, Abteilung Systembiochemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Katharina
K
Reglinski
Institut für Biochemie und Pathobiochemie, Abteilung Systembiochemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Marina
M
Keil
Institut für Biochemie und Pathobiochemie, Abteilung Systembiochemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Sabrina
S
Altendorf
Wolfson Imaging Centre, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom.
Dominic
D
Waithe
Wolfson Imaging Centre, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom.
Christian
C
Eggeling
Institut für Biochemie und Pathobiochemie, Abteilung Systembiochemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Wolfgang
W
Schliebs
Institut für Biochemie und Pathobiochemie, Abteilung Systembiochemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Ralf
R
Erdmann
D017209:Apoptosis / Q000502:physiology*; D003600:Cytosol / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism*; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D043222:Ubiquitin Thiolesterase
C000614264:PEX5 protein, human; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D010450:Endopeptidases; C108665:USP2 protein, human; D043222:Ubiquitin Thiolesterase