title: Respiratory chain complexes in dynamic mitochondria display a patchy distribution in life cells.
abstract: BACKGROUND
  Mitochondria, the main suppliers of cellular energy, are dynamic organelles that fuse and divide frequently. Constraining these processes impairs mitochondrial is closely linked to certain neurodegenerative diseases. It is proposed that functional mitochondrial dynamics allows the exchange of compounds thereby providing a rescue mechanism.
  
  
  RESULTS
  The question discussed in this paper is whether fusion and fission of mitochondria in different cell lines result in re-localization of respiratory chain (RC) complexes and of the ATP synthase. This was addressed by fusing cells containing mitochondria with respiratory complexes labelled with different fluorescent proteins and resolving their time dependent re-localization in living cells. We found a complete reshuffling of RC complexes throughout the entire chondriome in single HeLa cells within 2-3 h by organelle fusion and fission. Polykaryons of fused cells completely re-mixed their RC complexes in 10-24 h in a progressive way. In contrast to the recently described homogeneous mixing of matrix-targeted proteins or outer membrane proteins, the distribution of RC complexes and ATP synthase in fused hybrid mitochondria, however, was not homogeneous but patterned. Thus, complete equilibration of respiratory chain complexes as integral inner mitochondrial membrane complexes is a slow process compared with matrix proteins probably limited by complete fusion. In co-expressing cells, complex II is more homogenously distributed than complex I and V, resp. Indeed, this result argues for higher mobility and less integration in supercomplexes.
  
  
  CONCLUSIONS
  Our results clearly demonstrate that mitochondrial fusion and fission dynamics favours the re-mixing of all RC complexes within the chondriome. This permanent mixing avoids a static situation with a fixed composition of RC complexes per mitochondrion.
authors.affiliation: Institute of Kinematic Cell Research, Department of Biology, University of Frankfurt, Frankfurt/Main, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Muster
authors.forename: Wladislaw
authors.initials: W
authors.lastname: Kohl
authors.forename: Ilka
authors.initials: I
authors.lastname: Wittig
authors.forename: Valentina
authors.initials: V
authors.lastname: Strecker
authors.forename: Friederike
authors.initials: F
authors.lastname: Joos
authors.forename: Winfried
authors.initials: W
authors.lastname: Haase
authors.forename: Jürgen
authors.initials: J
authors.lastname: Bereiter-Hahn
authors.forename: Karin
authors.initials: K
authors.lastname: Busch
mesh_terms: D004586:Electrophoresis; D015180:Electrophoresis, Gel, Two-Dimensional; D006367:HeLa Cells; D006801:Humans; D008561:Membrane Fusion / Q000502:physiology; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000378:metabolism; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism; D010101:Oxygen Consumption
chemical_list: D025261:Mitochondrial Proton-Translocating ATPases