title: Mitochondrial uncoupler carbonyl cyanide M-chlorophenylhydrazone induces the multimer assembly and activity of repair enzyme protein L-isoaspartyl methyltransferase.
abstract: The protein L-isoaspartyl methyltransferase (PIMT) repairs damaged aspartyl residues in proteins. It is commonly described as a cytosolic protein highly expressed in brain tissues. Here, we report that PIMT is an active monomeric as well as a multimeric protein in mitochondria isolated from neuroblastoma cells. Upon treatments with mitochondrial uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP), PIMT monomers level decreased by half while that of PIMT multimers was higher. Gel electrophoresis under reducing conditions of CCCP-induced PIMT multimers led to PIMT monomers accumulation, indicating that multimers resulted from disulfide-linked PIMT monomers. The antioxidant ascorbic acid significantly lowered CCCP-induced formation of PIMT multimers, suggesting that reactive oxygen species contributed to PIMT multimerization. In addition, the elevation of PIMT multimers catalytic activity upon treatments with CCCP was severely inhibited by the reducing agent dithiothreitol. This indicated that PIMT monomers have lower enzymatic activity following CCCP treatments and that activation of PIMT multimers is essentially dependent on the formation of disulfide-linked monomers of PIMT. Furthermore, the perturbation of mitochondrial function by CCCP promoted the accumulation of damaged aspartyl residues in proteins with high molecular weights. Thus, this study demonstrates the formation of active PIMT multimers associated with mitochondria that could play a key role in repairing damaged proteins accumulating during mitochondrial dysfunction.
authors: The Montreal General Hospital, McGill University Health Centre, 1650 Cedar Avenue, Montreal, QC, H3G 1A4, Canada.
authors: Irvens
authors: I
authors: Fanélus
authors: Richard R
authors: RR
authors: Desrosiers
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004220:Disulfides / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D026601:Protein D-Aspartate-L-Isoaspartate Methyltransferase / Q000378:metabolism*; D055503:Protein Multimerization / Q000187:drug effects*; D021122:Protein Subunits / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology*
chemical_list: D004220:Disulfides; D021122:Protein Subunits; D017382:Reactive Oxygen Species; D014475:Uncoupling Agents; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D026601:Protein D-Aspartate-L-Isoaspartate Methyltransferase; D001205:Ascorbic Acid; D004229:Dithiothreitol