Molecular Machinery of Mitochondrial Fusion and Fission

Mitochondria generate energy by oxidative phosphorylation; play a crucial role in iron-sulfur cluster assembly; and participate in intermediary metabolism, calcium signaling, and apoptosis. They are bounded by a double membrane and contain ∼800 (yeast) to 1500 (human) different proteins. Although the vast majority of mitochondrial proteins are encoded in the nucleus and post-translationally imported into the organelle, a handful of proteins required for respiration are encoded by the mitochondrial genome. In many eukaryotic cell types, mitochondria continuously move along cytoskeletal tracks and frequently fuse and divide (1Bereiter-Hahn J. Int. Rev. Cytol. 1990; 122: 1-63Crossref PubMed Scopus (279) Google Scholar). In recent years, it became clear that this dynamic behavior is important for many mitochondrial functions in cell life and death (2Chan D.C. Cell. 2006; 125: 1241-1252Abstract Full Text Full Text PDF PubMed Scopus (1518) Google Scholar). Here, I will briefly summarize the cellular roles of mitochondrial dynamics and discuss the molecular machinery mediating mitochondrial membrane fusion and fission. Mitochondrial morphology and copy number depend on the balance of fusion and fission activities. A shift toward fusion enables the cell to build extended interconnected mitochondrial networks, whereas a shift toward fission generates numerous morphologically and functionally distinct small spherical organelles. This adaptation of the mitochondrial compartment to cellular demands is critical for a number of important processes (Fig. 1). Large mitochondrial networks are frequently found in metabolically active cells. They consist of extended and interconnected mitochondrial filaments and act as electrically united systems. These networks enable the transmission of mitochondrial membrane potential from oxygen-rich to oxygen-poor areas and thereby allow an efficient dissipation of energy in the cell (3Skulachev V.P. Trends Biochem. Sci. 2001; 26: 23-29Abstract Full Text Full Text PDF PubMed Scopus (368) Google Scholar). Furthermore, the connectivity of the mitochondrial network is an important factor that determines the cell's response to calcium signals (4Szabadkai G. Simoni A.M. Bianchi K. De Stefani D. Leo S. Wieckowski M.R. Rizzuto R. Biochim. Biophys. Acta. 2006; 1763: 442-449Crossref PubMed Scopus (161) Google Scholar), and fusion of mitochondria is an essential step in certain developmental processes such as embryonic development (5Chen H. Detmer S.A. Ewald A.J. Griffin E.E. Fraser S.E. Chan D.C. J. Cell Biol. 2003; 160: 189-200Crossref PubMed Scopus (1783) Google Scholar) and spermatogenesis (6Hales K.G. Fuller M.T. Cell. 1997; 90: 121-129Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar). In addition to its role in network formation, fusion serves to mix and unify the mitochondrial compartment, an activity that is thought to constitute a defense mechanism against aging. It is estimated that 1–5% of the oxygen consumed during oxidative phosphorylation is converted to ROS 2The abbreviations used are: ROS, reactive oxygen species; CMT, Charcot-Marie-Tooth disease. as an unavoidable by-product of respiratory chain function. As mtDNA is directly located at the site of ROS production, it is particularly vulnerable to ROS-mediated mutations. These mutations accumulate with age until a bioenergetic threshold is breached, resulting in mitochondrial dysfunction. The mitochondrial theory of aging predicts that an accumulation of mtDNA mutations eventually leads to age-associated pathologies and death (7Balaban R.S. Nemoto S. Finkel T. Cell. 2005; 120: 483-495Abstract Full Text Full Text PDF PubMed Scopus (3285) Google Scholar). Fusion of mitochondria counteracts the manifestation of respiratory deficiencies because it allows complementation of mtDNA gene products in heteroplasmic cells that have accumulated different somatic mutations (8Sato A. Nakada K. Hayashi J. Biochim. Biophys. Acta. 2006; 1763: 473-481Crossref PubMed Scopus (42) Google Scholar). Similar to fusion, mitochondrial fission also plays a key role in cell life and death. As mitochondria are propagated by growth and division of pre-existing organelles, mitochondrial inheritance depends on mitochondrial fission during cytokinesis (9Warren G. Wickner W. Cell. 1996; 84: 395-400Abstract Full Text Full Text PDF PubMed Scopus (228) Google Scholar). Furthermore, mitochondrial division is important for several developmental and cell differentiation processes, including embryonic development in Caenorhabditis elegans (10Labrousse A.M. Zappaterra M.D. Rube D.A. van der Bliek A.M. Mol. Cell. 1999; 4: 815-826Abstract Full Text Full Text PDF PubMed Scopus (513) Google Scholar) and formation of synapses and dendritic spines in neurons (11Li Z. Okamoto K. Hayashi Y. Sheng M. Cell. 2004; 119: 873-887Abstract Full Text Full Text PDF PubMed Scopus (1126) Google Scholar). Last but not least, the mitochondrial fission machinery actively participates in the programmed cell death pathway (apoptosis) by inducing fragmentation of the mitochondrial network prior to cytochrome c release and caspase activation (12Youle R.J. Karbowski M. Nat. Rev. Mol. Cell Biol. 2005; 6: 657-663Crossref PubMed Scopus (622) Google Scholar). The major components of the mitochondrial fusion and fission machineries have been evolutionarily conserved from yeast to man (Table 1). Due to this conservation and the availability of sophisticated genetic, cytological, and biochemical assays, bakers' yeast (Saccharomyces cerevisiae) emerged as one of the prime model organisms to study the molecular mechanisms of mitochondrial membrane fusion and fission (13Okamoto K. Shaw J.M. Annu. Rev. Genet. 2005; 39: 503-536Crossref PubMed Scopus (594) Google Scholar, 14Merz S. Hammermeister M. Altmann K. Dürr M. Westermann B. Biol. Chem. 2007; 388: 917-926Crossref PubMed Scopus (36) Google Scholar, 15Hoppins S. Lackner L. Nunnari J. Annu. Rev. Biochem. 2007; 76: 751-780Crossref PubMed Scopus (611) Google Scholar).TABLE 1Core components of the mitochondrial fusion and fission machineriesProcess/yeastOrthologs in higher eukaryotesLocationProposed functionFusion Fzo1MFN1 and MFN2 (mammals), FZO and DMFN (D. melanogaster)OMOM fusion Ugo1OMCoordination of OM and IM fusion Mgm1OPA1 (mammals)IM and IMSIM fusionFission Dnm1DRP1/DLP1 (mammals), DRP-1 (C. elegans), ADL1 and ADL2 (A. thaliana)Cytosol and OMOM fission Fis1hFis1 (humans)OMReceptor for OM fission machinery Mdv1Cytosol and OMAdaptor between Fis1 and Dnm1 Caf4Cytosol and OMRedundant with Mdv1 Open table in a new tab The core machinery mediating fusion in yeast consists of three proteins: Fzo1 and Ugo1 in the outer membrane and Mgm1, an intermembrane space protein anchored to the inner membrane (Fig. 2). Yeast cells lacking one of these components contain fragmented mitochondria and have defects in mtDNA inheritance. Exchange of mitochondrial matrix content is blocked both in vivo and in vitro, indicating that a block of fusion is the primary defect in Δfzo1, Δugo1, and Δmgm1 deletion mutants (16Rapaport D. Brunner M. Neupert W. Westermann B. J. Biol. Chem. 1998; 273: 20150-20155Abstract Full Text Full Text PDF PubMed Scopus (293) Google Scholar, 17Hermann G.J. Thatcher J.W. Mills J.P. Hales K.G. Fuller M.T. Nunnari J. Shaw J.M. J. Cell Biol. 1998; 143: 359-373Crossref PubMed Scopus (426) Google Scholar, 18Meeusen S. DeVay R. Block J. Cassidy-Stone A. Wayson S. McCaffery J.M. Nunnari J. Cell. 2006; 127: 383-395Abstract Full Text Full Text PDF PubMed Scopus (349) Google Scholar, 19Meeusen S. McCaffery J.M. Nunnari J. Science. 2004; 305: 1747-1752Crossref PubMed Scopus (346) Google Scholar, 20Sesaki H. Jensen R.E. J. Cell Biol. 2001; 152: 1123-1134Crossref PubMed Scopus (193) Google Scholar, 21Wong E.D. Wagner J.A. Scott S.V. Okreglak V. Holewinske T.J. Cassidy-Stone A. Nunnari J. J. Cell Biol. 2003; 160: 303-311Crossref PubMed Scopus (194) Google Scholar). Fzo1 is a large GTPase that assembles into a high molecular mass complex in the outer membrane. It has two transmembrane regions, with the major parts of the protein extending into the cytosol and a short loop exposed to the intermembrane space. The large N-terminal part consists of a GTPase domain flanked by two predicted coiled coils. The smaller C-terminal part contains another coiled-coil region (16Rapaport D. Brunner M. Neupert W. Westermann B. J. Biol. Chem. 1998; 273: 20150-20155Abstract Full Text Full Text PDF PubMed Scopus (293) Google Scholar, 17Hermann G.J. Thatcher J.W. Mills J.P. Hales K.G. Fuller M.T. Nunnari J. Shaw J.M. J. Cell Biol. 1998; 143: 359-373Crossref PubMed Scopus (426) Google Scholar, 22Fritz S. Rapaport D. Klanner E. Neupert W. Westermann B. J. Cell Biol. 2001; 152: 683-692Crossref PubMed Scopus (121) Google Scholar). Fzo1-related proteins have been conserved throughout the fungal and animal kingdoms. Drosophila FZO, the founding member of the protein family, plays a highly specialized role in spermatogenesis (6Hales K.G. Fuller M.T. Cell. 1997; 90: 121-129Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar), whereas a related protein, DMFN, is widely expressed in male and female flies (23Hwa J.J. Hiller M.A. Fuller M.T. Santel A. Mech. Dev. 2002; 116: 213-216Crossref PubMed Scopus (55) Google Scholar). Mammalian cells contain two ubiquitously expressed homologs termed mitofusins (MFN1 and MFN2). Metazoan mitofusins share the same topology and domain organization with yeast Fzo1, with the exception that they lack the most N-terminal coiled-coil region (24Rojo M. Legros F. Chateau D. Lombes A. J. Cell Sci. 2002; 115: 1663-1674Crossref PubMed Google Scholar). Ugo1 is a yeast mitochondrial outer membrane protein that contains up to five transmembrane regions (20Sesaki H. Jensen R.E. J. Cell Biol. 2001; 152: 1123-1134Crossref PubMed Scopus (193) Google Scholar, 25Coonrod E.M. Karren M.A. Shaw J.M. Traffic. 2007; 8: 500-511Crossref PubMed Scopus (45) Google Scholar). Homologs of Ugo1 in higher organisms are unknown. Mgm1, a dynamin-related GTPase in the intermembrane space, contains a cleavable N-terminal presequence for import, a hydrophobic transmembrane anchor, a GTPase domain, a middle domain, and a GTPase effector domain (13Okamoto K. Shaw J.M. Annu. Rev. Genet. 2005; 39: 503-536Crossref PubMed Scopus (594) Google Scholar, 21Wong E.D. Wagner J.A. Scott S.V. Okreglak V. Holewinske T.J. Cassidy-Stone A. Nunnari J. J. Cell Biol. 2003; 160: 303-311Crossref PubMed Scopus (194) Google Scholar). Mgm1 is present in two isoforms: a large form anchored in the inner membrane and a small form lacking the hydrophobic membrane anchor. The small form is generated by alternative processing by the rhomboid-related inner membrane protease, Pcp1 (26Herlan M. Vogel F. Bornhövd C. Neupert W. Reichert A.S. J. Biol. Chem. 2003; 278: 27781-27788Abstract Full Text Full Text PDF PubMed Scopus (297) Google Scholar, 27McQuibban G.A. Saurya S. Freeman M. Nature. 2003; 423: 537-541Crossref PubMed Scopus (314) Google Scholar). OPA1, the mammalian homolog of Mgm1, is present in even greater variety because eight tissue-specific splice variants exist in addition to the large and small isoforms (28Olichon A. Guillou E. Delettre C. Landes T. Arnaune-Pelloquin L. Emorine L.J. Mils V. Daloyau M. Hamel C. Amati-Bonneau P. Bonneau D. Reynier P. Lenaers G. Belenguer P. Biochim. Biophys. Acta. 2006; 1763: 500-509Crossref PubMed Scopus (180) Google Scholar). As double membrane-bounded organelles, mitochondria face the topological problem that they have to fuse four membranes in a coordinated manner. How is this achieved? The first step in cellular membrane fusion events is the formation of trans complexes involving proteins on the surface of both fusion partners. This docking step ensures specificity of the fusion reaction and mediates apposition of adjacent membranes. Several lines of evidence indicate that Fzo1/mitofusins play a key role in formation of the trans complex. First, wild-type mitochondria fail to fuse with mitochondria lacking Fzo1/mitofusins (19Meeusen S. McCaffery J.M. Nunnari J. Science. 2004; 305: 1747-1752Crossref PubMed Scopus (346) Google Scholar, 29Koshiba T. Detmer S.A. Kaiser J.T. Chen H. McCaffery J.M. Chan D.C. Science. 2004; 305: 858-862Crossref PubMed Scopus (659) Google Scholar); second, a mitofusin docking complex formed on distinct apposing membranes has been identified by immunoprecipitation (30Ishihara N. Eura Y. Mihara K. J. Cell Sci. 2004; 117: 6535-6546Crossref PubMed Scopus (509) Google Scholar); and third, the C-terminal heptad repeat regions of MFN1 form a dimeric antiparallel coiled coil that is ideally suited to tether the membranes of adjacent mitochondria together (29Koshiba T. Detmer S.A. Kaiser J.T. Chen H. McCaffery J.M. Chan D.C. Science. 2004; 305: 858-862Crossref PubMed Scopus (659) Google Scholar). The second step in membrane fusion is lipid bilayer mixing. The capability to form α-helical rods by pairing of coiled-coil domains is a hallmark of membrane fusion machineries such as SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) and viral fusion proteins. Formation of these rods draws apposing membranes close together and thereby initiates lipid bilayer mixing (31Weber T. Zemelman B.V. McNew J.A. Westermann B. M. F. Cell. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). Fzo1/mitofusins domains that predicted to present in a they have several coiled-coil regions, two transmembrane and a GTPase domain, energy to the energy of lipid bilayer mixing. Although it has not been activity is to act as for the outer it is clear that Fzo1/mitofusins play a role in this (13Okamoto K. Shaw J.M. Annu. Rev. Genet. 2005; 39: 503-536Crossref PubMed Scopus (594) Google Scholar, 15Hoppins S. Lackner L. Nunnari J. Annu. Rev. Biochem. 2007; 76: 751-780Crossref PubMed Scopus (611) Google Scholar, B. Biochim. Biophys. Acta. 2003; PubMed Scopus Google Scholar). of outer membrane fusion, of the mitochondrial inner membranes mitochondrial content mixing in vivo and in that fusion of the inner membrane is particularly to dissipation of the membrane potential and functionally from fusion of the outer these indicate that a distinct fusion machinery is present in the inner membrane (19Meeusen S. McCaffery J.M. Nunnari J. Science. 2004; 305: 1747-1752Crossref PubMed Scopus (346) Google Scholar, F. C. Guillou E. Belenguer P. Lombes A. M. 2005; 6: PubMed Scopus Google Scholar). of mutants a key role to Mgm1 as a of inner membrane Similar to Fzo1 in the outer Mgm1 has the capability to form trans complexes that tether apposing inner membranes. fusion is blocked also in mitochondria of that defects in a inner membrane This that Mgm1 and its mammalian OPA1, play a key role in inner membrane lipid mixing S. Lackner L. Nunnari J. Annu. Rev. Biochem. 2007; 76: 751-780Crossref PubMed Scopus (611) Google Scholar, 18Meeusen S. DeVay R. Block J. Cassidy-Stone A. Wayson S. McCaffery J.M. Nunnari J. Cell. 2006; 127: 383-395Abstract Full Text Full Text PDF PubMed Scopus (349) Google Scholar). activity of the machineries in the outer and inner membranes the of double membrane Fzo1 is found in the mitochondrial outer and inner and mutants that of Fzo1 with the inner membrane defects in mitochondrial fusion in vivo G.J. Thatcher J.W. Mills J.P. Hales K.G. Fuller M.T. Nunnari J. Shaw J.M. J. Cell Biol. 1998; 143: 359-373Crossref PubMed Scopus (426) Google Scholar, 22Fritz S. Rapaport D. Klanner E. Neupert W. Westermann B. J. Cell Biol. 2001; 152: 683-692Crossref PubMed Scopus (121) Google Scholar). These that of the outer membrane fusion machinery with the inner membrane are required to double membrane As Ugo1 has been found in a complex with Fzo1 and Mgm1 E.D. Wagner J.A. Scott S.V. Okreglak V. Holewinske T.J. Cassidy-Stone A. Nunnari J. J. Cell Biol. 2003; 160: 303-311Crossref PubMed Scopus (194) Google Scholar, H. Jensen R.E. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar), it is that Ugo1 plays an important role in outer and inner membrane fusion events in The core machinery of mitochondrial fission in yeast consists of four proteins: Fis1 in the outer membrane and three proteins and that at of mitochondrial division on the surface (Fig. Yeast cells in outer membrane fission contain interconnected mitochondrial to fusion by fission W. McCaffery J.M. S. A. Nunnari J. Shaw J.M. Nat. Cell Biol. 1999; PubMed Scopus Google Scholar, H. Jensen R.E. J. Cell Biol. 1999; PubMed Scopus Google Scholar, Nunnari J. J. Cell Biol. PubMed Scopus Google Scholar, A. McCaffery J.M. Shaw J.M. J. Cell Biol. PubMed Scopus Google Scholar, E.E. J. Chan D.C. J. Cell Biol. 2005; PubMed Scopus Google Scholar). Yeast Dnm1 is a dynamin-related protein an N-terminal GTPase domain, a middle domain, an of and a C-terminal GTPase effector Dnm1 assembles into on mitochondria in a dynamic A. T. Mol. Biol. Cell. 2003; PubMed Scopus Google Scholar). dynamin-related proteins have been to play a role in mitochondrial fission in also termed and higher and (13Okamoto K. Shaw J.M. Annu. Rev. Genet. 2005; 39: 503-536Crossref PubMed Scopus (594) Google Scholar). Fis1 is a outer membrane protein that is on the mitochondrial surface A. McCaffery J.M. Shaw J.M. J. Cell Biol. PubMed Scopus Google Scholar). N-terminal domain a repeat This domain two for the of fission from the cytosol Y. Chan D.C. Sci. S. A. 2007; PubMed Scopus Google Scholar). proteins in have been evolutionarily highly conserved in and Y. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). Mdv1 and are two related proteins that functions in mitochondrial fission and share the same domain organization Nunnari J. J. Cell Biol. PubMed Scopus Google Scholar, E.E. J. Chan D.C. J. Cell Biol. 2005; PubMed Scopus Google Scholar). N-terminal contains two that with a coiled-coil domain is thought to and a C-terminal repeat region is predicted to form a that to Dnm1 Y. Chan D.C. Sci. S. A. 2007; PubMed Scopus Google Scholar, Okreglak V. K. Nunnari J. J. Cell Biol. 2002; PubMed Scopus Google Scholar). homologs of Mdv1 and in are not of mitochondrial division that Dnm1 is the key mediating membrane (13Okamoto K. Shaw J.M. Annu. Rev. Genet. 2005; 39: 503-536Crossref PubMed Scopus (594) Google Scholar, 14Merz S. Hammermeister M. Altmann K. Dürr M. Westermann B. Biol. Chem. 2007; 388: 917-926Crossref PubMed Scopus (36) Google Scholar, 15Hoppins S. Lackner L. Nunnari J. Annu. Rev. Biochem. 2007; 76: 751-780Crossref PubMed Scopus (611) Google Scholar). Fis1 functions as a membrane and Mdv1 and as proteins to Dnm1 to the of mitochondrial fission. In a first step of the division Fis1 and the dynamic of Dnm1 on the mitochondrial As it has been that Dnm1 into filaments extended in E. E.M. M. J.A. McCaffery J.M. Nunnari J. J. Cell Biol. 2005; PubMed Scopus Google Scholar), it that Dnm1 on mitochondria assembles into the As the of Dnm1 filaments depends on the and of the mitochondrial membranes (13Okamoto K. Shaw J.M. Annu. Rev. Genet. 2005; 39: 503-536Crossref PubMed Scopus (594) Google Scholar, 15Hoppins S. Lackner L. Nunnari J. Annu. Rev. Biochem. 2007; 76: 751-780Crossref PubMed Scopus (611) Google Scholar, E. E.M. M. J.A. McCaffery J.M. Nunnari J. J. Cell Biol. 2005; PubMed Scopus Google Scholar). In this the of Dnm1 to that of that act in numerous membrane events G.J. Nat. Rev. Mol. Cell Biol. 2004; PubMed Scopus Google Scholar). is fission of the inner membrane. It is that the activity of Dnm1 is to both mitochondrial membranes evidence to the of a division machinery in the inner membrane. The of a is whereas the of Dnm1 is E. E.M. M. J.A. McCaffery J.M. Nunnari J. J. Cell Biol. 2005; PubMed Scopus Google Scholar). the of the at the site of division to allow formation of Dnm1 it has been that Dnm1 on mitochondria a division of the it with a prior A. T. Mol. Biol. Cell. 2003; PubMed Scopus Google Scholar). It is that is a of inner membrane division at this In of deletion mutants in yeast and mutants in C. elegans that inner membrane division of matrix in the of outer membrane division (10Labrousse A.M. Zappaterra M.D. Rube D.A. van der Bliek A.M. Mol. Cell. 1999; 4: 815-826Abstract Full Text Full Text PDF PubMed Scopus (513) Google Scholar, S. N. A. Westermann B. J. Cell Sci. 2003; 116: PubMed Scopus Google Scholar). components have been to to inner membrane in yeast and in is a mitochondrial inner membrane protein coiled-coil domains in the of and of the inner membrane to inner membrane fission whereas mutants lacking contain mitochondria M. S. Vogel F. S. Neupert W. Westermann B. J. Cell Biol. 2003; 160: PubMed Scopus Google Scholar). is an protein in the inner membrane of mammalian of fragmentation of the mitochondrial whereas in formation of highly mitochondria D. F. K. R. J. Santel A. J. Cell Sci. 2005; PubMed Scopus Google Scholar). on these a role in inner membrane fission has been to the lack of assays, it is to a role of and in inner membrane balance of fusion and fission is required to mitochondrial morphology in In response to a shift toward fission fusion allows the cell to the mitochondrial network and its morphology to the cellular The of the balance is from the that defects in mitochondrial dynamics to a variety of (Fig. 1). is the gene for a form of (28Olichon A. Guillou E. Delettre C. Landes T. Arnaune-Pelloquin L. Emorine L.J. Mils V. Daloyau M. Hamel C. Amati-Bonneau P. Bonneau D. Reynier P. Lenaers G. Belenguer P. Biochim. Biophys. Acta. 2006; 1763: 500-509Crossref PubMed Scopus (180) Google Scholar), and mutations in the MFN2 gene to a by the of neurons A. Biochim. Biophys. Acta. 2006; 1763: PubMed Scopus Google Scholar). defects in mitochondrial division have been to with a involving defects A. P. 2006; 8: PubMed Scopus Google Scholar). the of mitochondrial and it is clear that the of fusion and fission Although the machineries of fusion and fission have been highly the mechanisms to are A will the of that have in different eukaryotic cell role as core components of the fusion machinery Fzo1/mitofusins prime for mechanisms on the FZO protein in Drosophila a highly specialized role in spermatogenesis and is expressed in during a developmental (6Hales K.G. Fuller M.T. Cell. 1997; 90: 121-129Abstract Full Text Full Text PDF PubMed Scopus (478) Google Scholar). mammalian and mitochondrial fusion by the and of activity is required both in and in to an of mitochondrial and programmed cell death M. R.J. Nature. 2006; PubMed Scopus Google Scholar). in a cell such as two Fzo1 have been the protein of Fzo1 by a mechanism in cells M. Westermann B. T. J. Cell Biol. 2006; PubMed Scopus Google Scholar), whereas of Fzo1 is and not in cell cells A. R.J. J. Biol. Chem. 2005; Full Text Full Text PDF PubMed Scopus Google Scholar). the key of mitochondrial division in mammalian is to complex It with termed an protein of the outer membrane that mitochondrial fission by of its activity N. Y. M. S. S. 2006; PubMed Scopus Google Scholar, R. S. S. T. E. Y. M. K. H. H. R. S. J. 2006; PubMed Scopus Google Scholar). The of is by with the small Z. R. H. Biol. 2004; Full Text Full Text PDF PubMed Google Scholar), and phosphorylation of by fragmentation of mitochondria during N. N. A. T. Mihara K. J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar). Although several mitochondrial dynamics have been Y. Z. Jensen R.E. H. Trends Cell Biol. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar), the to the of the of mitochondrial fusion and fission with the developmental and of eukaryotic cells. It is to that the will many new components and mechanisms to the dynamic behavior of mitochondria in cell life and death. I and for on the