title: Mitochondrial chaperone DnaJA3 induces Drp1-dependent mitochondrial fragmentation.
abstract: Mitochondrial morphology is dynamic and controlled by coordinated fusion and fission pathways. The role of mitochondrial chaperones in mitochondrial morphological changes and pathology is currently unclear. Here we report that altered levels of DnaJA3 (Tid1/mtHsp40) a mitochondrial member of the DnaJ protein family, and heat shock protein (Hsp) co-chaperone of matrix 70 kDa Hsp70 (mtHsp70/mortalin/HSPA9), induces mitochondrial fragmentation. Suppression of DnaJA3 induced mitochondrial fragmentation in HeLa cells. Elevated levels of DnaJA3 in normal Hs68 fibroblast cells and HeLa, SKN-SH, U87 and U251 cancer cell lines induces mitochondrial fragmentation. Mitochondrial fragmentation induction was not observed in HeLa cells when other DnaJA family members, or mitochondrial DnaJ protein HSC20, were ectopically expressed, indicating that the effects on mitochondrial morphology were specific to DnaJA3. We show that the DnaJ domain (amino acids 88-168) of DnaJA3 is sufficient for the induction of mitochondrial fragmentation. Furthermore, an H121Q point mutation of the DnaJ domain, which abrogates interaction and activation of mtHsp70 ATPase, eliminates fragmentation induced by DnaJA3. This suggests that DnaJA3 interaction with mtHsp70 may be critical in mitochondrial morphological changes. DnaJA3-induced mitochondrial fragmentation was dependent on fission factor dynamin-related protein 1 (Drp1). Ectopic expression of the mitofusins (Mfn1 and Mfn2), however, does not rescue DnaJA3-induced mitochondrial fragmentation. Lastly, elevated levels of DnaJA3 inducing mitochondrial fragmentation were associated with reduction in cell viability. Taken together, elevated DnaJA3 induces Drp1-depedendent mitochondrial fragmentation and decreased cell viability.
authors.affiliation: Southern Alberta Cancer Research Institute, Department of Biochemistry and Molecular Biology, University of Calgary, Alberta, Canada.
authors.forename: Adam N
authors.initials: AN
authors.lastname: Elwi
authors.forename: Byoungchun
authors.initials: B
authors.lastname: Lee
authors.forename: H Christopher
authors.initials: HC
authors.lastname: Meijndert
authors.forename: Janice E A
authors.initials: JE
authors.lastname: Braun
authors.forename: Sung-Woo
authors.initials: SW
authors.lastname: Kim
mesh_terms: D001665:Binding Sites / Q000235:genetics; D045744:Cell Line, Tumor; D002470:Cell Survival; D002478:Cells, Cultured; D034281:Dynamins; D005434:Flow Cytometry; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D053078:Membrane Potential, Mitochondrial; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: C120664:DNAJA3 protein, human; C490651:HSCB protein, human; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D008869:Microtubule-Associated Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D017382:Reactive Oxygen Species; D049452:Green Fluorescent Proteins; D020558:GTP Phosphohydrolases; C470018:MFN2 protein, human; C470017:Mfn1 protein, human; C110768:DNM1L protein, human; D034281:Dynamins