scholarly journals The Yeast Dynamin-like Protein, Mgm1p, Functions on the Mitochondrial Outer Membrane to Mediate Mitochondrial Inheritance

1999 ◽  
Vol 144 (4) ◽  
pp. 711-720 ◽  
Author(s):  
Kelly A. Shepard ◽  
Michael P. Yaffe
Keyword(s):  
Mitochondrial Genome ◽  
Outer Membrane ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Mitochondrial Inheritance ◽  
Gene Encoding ◽  
Yeast Saccharomyces Cerevisiae ◽  
High Molecular Weight Complex ◽  
Mitochondrial Distribution ◽  
Mutant Phenotypes

The mdm17 mutation causes temperature-dependent defects in mitochondrial inheritance, mitochondrial morphology, and the maintenance of mitochondrial DNA in the yeast Saccharomyces cerevisiae. Defects in mitochondrial transmission to daughter buds and changes in mitochondrial morphology were apparent within 30 min after shifting cells to 37°C, while loss of the mitochondrial genome occurred after 4–24 h at the elevated temperature. The mdm17 lesion mapped to MGM1, a gene encoding a dynamin-like GTPase previously implicated in mitochondrial genome maintenance, and the cloned MGM1 gene complements all of the mdm17 mutant phenotypes. Cells with an mgm1-null mutation displayed aberrant mitochondrial inheritance and morphology. A version of mgm1 mutated in a conserved residue in the putative GTP-binding site was unable to complement any of the mutant defects. It also caused aberrant mitochondrial distribution and morphology when expressed at high levels in cells that also contained a wild-type copy of the gene. Mgm1p was localized to the mitochondrial outer membrane and fractionated as a component of a high molecular weight complex. These results indicate that Mgm1p is a mitochondrial inheritance and morphology component that functions on the mitochondrial surface.

scholarly journals Regulation of mitochondrial morphology and inheritance by Mdm10p, a protein of the mitochondrial outer membrane.

1994 ◽  
Vol 126 (6) ◽  
pp. 1361-1373 ◽  
Author(s):  
L F Sogo ◽  
M P Yaffe
Keyword(s):  
Outer Membrane ◽  
Yeast Cells ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Wild Type ◽  
Giant Mitochondria ◽  
Mitochondrial Distribution ◽  
Rapid Restoration ◽  
Mutant Phenotypes ◽  
Mutant Cells

Yeast cells with the mdm10 mutation possess giant spherical mitochondria and are defective for mitochondrial inheritance. The giant mitochondria display classical features of mitochondrial ultrastructure, yet they appear incapable of movement or division. Genetic analysis indicated that the mutant phenotypes resulted from a single nuclear mutation, and the isolated MDM10 gene restored wild-type mitochondrial distribution and morphology when introduced into mutant cells. MDM10 encodes a protein of 56.2 kD located in the mitochondrial outer membrane. Depletion of Mdm10p from cells led to a condensation of normally extended, tubular mitochondria into giant spheres, and reexpression of the protein resulted in a rapid restoration of normal mitochondrial morphology. These results demonstrate that Mdm10p can control mitochondrial morphology, and that it plays a role in the inheritance of mitochondria.

scholarly journals Prohibitin Family Members Interact Genetically with Mitochondrial Inheritance Components in Saccharomyces cerevisiae

1998 ◽  
Vol 18 (7) ◽  
pp. 4043-4052 ◽  
Author(s):  
Karen H. Berger ◽  
Michael P. Yaffe
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Outer Membrane ◽  
Integral Membrane Proteins ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Mitochondrial Inheritance ◽  
Loss Of Function ◽  
Wild Type ◽  
Mitochondrial Inner Membrane ◽  
Synthetically Lethal

ABSTRACT Phb2p, a homolog of the tumor suppressor protein prohibitin, was identified in a genetic screen for suppressors of the loss of Mdm12p, a mitochondrial outer membrane protein required for normal mitochondrial morphology and inheritance in Saccharomyces cerevisiae. Phb2p and its homolog, prohibitin (Phb1p), were localized to the mitochondrial inner membrane and characterized as integral membrane proteins which depend on each other for their stability. In otherwise wild-type genetic backgrounds, null mutations in PHB1 andPHB2 did not confer any obvious phenotypes. However, loss of function of either PHB1 or PHB2 in cells with mitochondrial DNA deleted led to altered mitochondrial morphology, and phb1 or phb2 mutations were synthetically lethal when combined with a mutation in any of three mitochondrial inheritance components of the mitochondrial outer membrane, Mdm12p, Mdm10p, and Mmm1p. These results provide the first evidence of a role for prohibitin in mitochondrial inheritance and in the regulation of mitochondrial morphology.

scholarly journals A Role for Ubiquitination in Mitochondrial Inheritance in Saccharomyces cerevisiae

1999 ◽  
Vol 145 (6) ◽  
pp. 1199-1208 ◽  
Author(s):  
Harold A. Fisk ◽  
Michael P. Yaffe
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Site Directed Mutagenesis ◽  
Temperature Sensitive ◽  
Mitochondrial Inheritance ◽  
Wild Type ◽  
Gene Encoding ◽  
Yeast Saccharomyces Cerevisiae ◽  
Protein Ubiquitination ◽  
Ubiquitin Ligase Activity ◽  
Mitochondrial Distribution

The smm1 mutation suppresses defects in mitochondrial distribution and morphology caused by the mdm1-252 mutation in the yeast Saccharomyces cerevisiae. Cells harboring only the smm1 mutation themselves display temperature-sensitive growth and aberrant mitochondrial inheritance and morphology at the nonpermissive temperature. smm1 maps to RSP5, a gene encoding an essential ubiquitin-protein ligase. The smm1 defects are suppressed by overexpression of wild-type ubiquitin but not by overexpression of mutant ubiquitin in which lysine-63 is replaced by arginine. Furthermore, overexpression of this mutant ubiquitin perturbs mitochondrial distribution and morphology in wild-type cells. Site-directed mutagenesis revealed that the ubiquitin ligase activity of Rsp5p is essential for its function in mitochondrial inheritance. A second mutation, smm2, which also suppressed mdm1-252 defects, but did not cause aberrant mitochondrial distribution and morphology, mapped to BUL1, encoding a protein interacting with Rsp5p. These results indicate that protein ubiquitination mediated by Rsp5p plays an essential role in mitochondrial inheritance, and reveal a novel function for protein ubiquitination.

scholarly journals The myosin-related motor protein Myo2 is an essential mediator of bud-directed mitochondrial movement in yeast

2011 ◽  
Vol 194 (3) ◽  
pp. 473-488 ◽  
Author(s):  
Johannes Förtsch ◽  
Eric Hummel ◽  
Melanie Krist ◽  
Benedikt Westermann
Keyword(s):  
Synthetic Lethality ◽  
Motor Protein ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Gene Encoding ◽  
Mitochondrial Movement ◽  
Isolated Mitochondria ◽  
Mitochondrial Distribution ◽  
Synthetically Lethal ◽  
Guanosine Triphosphatase

The inheritance of mitochondria in yeast depends on bud-directed transport along actin filaments. It is a matter of debate whether anterograde mitochondrial movement is mediated by the myosin-related motor protein Myo2 or by motor-independent mechanisms. We show that mutations in the Myo2 cargo binding domain impair entry of mitochondria into the bud and are synthetically lethal with deletion of the YPT11 gene encoding a rab-type guanosine triphosphatase. Mitochondrial distribution defects and synthetic lethality were rescued by a mitochondria-specific Myo2 variant that carries a mitochondrial outer membrane anchor. Furthermore, immunoelectron microscopy revealed Myo2 on isolated mitochondria. Thus, Myo2 is an essential and direct mediator of bud-directed mitochondrial movement in yeast. Accumulating genetic evidence suggests that maintenance of mitochondrial morphology, Ypt11, and retention of mitochondria in the bud contribute to Myo2-dependent inheritance of mitochondria.

scholarly journals MMM1 encodes a mitochondrial outer membrane protein essential for establishing and maintaining the structure of yeast mitochondria.

1994 ◽  
Vol 126 (6) ◽  
pp. 1375-1391 ◽  
Author(s):  
S M Burgess ◽  
M Delannoy ◽  
R E Jensen
Keyword(s):  
Outer Membrane ◽  
Cell Function ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Cell Periphery ◽  
Permissive Temperature ◽  
Yeast Saccharomyces Cerevisiae ◽  
Mitochondrial Structure

In the yeast Saccharomyces cerevisiae, mitochondria are elongated organelles which form a reticulum around the cell periphery. To determine the mechanism by which mitochondrial shape is established and maintained, we screened yeast mutants for those defective in mitochondrial morphology. One of these mutants, mmm1, is temperature-sensitive for the external shape of its mitochondria. At the restrictive temperature, elongated mitochondria appear to quickly collapse into large, spherical organelles. Upon return to the permissive temperature, wild-type mitochondrial structure is restored. The morphology of other cellular organelles is not affected in mmm1 mutants, and mmm1 does not disrupt normal actin or tubulin organization. Cells disrupted in the MMM1 gene are inviable when grown on nonfermentable carbon sources and show abnormal mitochondrial morphology at all temperatures. The lethality of mmm1 mutants appears to result from the inability to segregate the aberrant-shaped mitochondria into daughter cells. Mitochondrial structure is therefore important for normal cell function. Mmm1p is located in the mitochondrial outer membrane, with a large carboxyl-terminal domain facing the cytosol. We propose that Mmm1p maintains mitochondria in an elongated shape by attaching the mitochondrion to an external framework, such as the cytoskeleton.

scholarly journals Gag3p, an Outer Membrane Protein Required for Fission of Mitochondrial Tubules

2000 ◽  
Vol 151 (2) ◽  
pp. 333-340 ◽  
Author(s):  
Peter Fekkes ◽  
Kelly A. Shepard ◽  
Michael P. Yaffe
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Fission ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Gene Products ◽  
Mitochondrial Fragmentation ◽  
Gene Encoding ◽  
Peripheral Protein ◽  
And Function ◽  
Two Hybrid

Mitochondrial morphology and function depend on MGM1, a Saccharomyces cerevisiae gene encoding a dynamin-like protein of the mitochondrial outer membrane. Here, we show that mitochondrial fragmentation and mitochondrial genome loss caused by lesions in MGM1 are suppressed by three novel mutations, gag1, gag2, and gag3 (for glycerol-adapted growth). Cells with any of the gag mutations displayed aberrant mitochondrial morphology characterized by elongated, unbranched tubes and highly fenestrated structures. Additionally, each of the gag mutations prevented mitochondrial fragmentation caused by loss of the mitochondrial fusion factor, Fzo1p, or by treatment of cells with sodium azide. The gag1 mutation mapped to DNM1 that encodes a dynamin-related protein required for mitochondrial fission. GAG3 encodes a novel WD40-repeat protein previously found to interact with Dnm1p in a two-hybrid assay. Gag3p was localized to mitochondria where it was found to associate as a peripheral protein on the cytosolic face of the outer membrane. This association requires neither the DNM1 nor GAG2 gene products. However, the localization of Dnm1p to the mitochondrial outer membrane is substantially reduced by the gag2 mutation, but unaffected by loss of Gag3p. These results indicate that Gag3p plays a distinct role on the mitochondrial surface to mediate the fission of mitochondrial tubules.

scholarly journals Regulation of mitochondrial fusion by the F-box protein Mdm30 involves proteasome-independent turnover of Fzo1

2006 ◽  
Vol 173 (5) ◽  
pp. 645-650 ◽  
Author(s):  
Mafalda Escobar-Henriques ◽  
Benedikt Westermann ◽  
Thomas Langer
Keyword(s):  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Critical Role ◽  
Mitochondrial Fusion ◽  
Yeast Cells ◽  
Mitochondrial Outer Membrane ◽  
Central Component ◽  
Mitochondrial Morphology ◽  
Proteolytic Pathway ◽  
F Box Protein

Mitochondrial morphology depends on balanced fusion and fission events. A central component of the mitochondrial fusion apparatus is the conserved GTPase Fzo1 in the outer membrane of mitochondria. Mdm30, an F-box protein required for mitochondrial fusion in vegetatively growing cells, affects the cellular Fzo1 concentration in an unknown manner. We demonstrate that mitochondrial fusion requires a tight control of Fzo1 levels, which is ensured by Fzo1 turnover. Mdm30 binds to Fzo1 and, dependent on its F-box, mediates proteolysis of Fzo1. Unexpectedly, degradation occurs along a novel proteolytic pathway not involving ubiquitylation, Skp1–Cdc53–F-box (SCF) E3 ubiquitin ligase complexes, or 26S proteasomes, indicating a novel function of an F-box protein. This contrasts to the ubiquitin- and proteasome-dependent turnover of Fzo1 in α-factor–arrested yeast cells. Our results therefore reveal not only a critical role of Fzo1 degradation for mitochondrial fusion in vegetatively growing cells but also the existence of two distinct proteolytic pathways for the turnover of mitochondrial outer membrane proteins.

scholarly journals The Dynamin-Related Gtpase, Mgm1p, Is an Intermembrane Space Protein Required for Maintenance of Fusion Competent Mitochondria

2000 ◽  
Vol 151 (2) ◽  
pp. 341-352 ◽  
Author(s):  
Edith D. Wong ◽  
Jennifer A. Wagner ◽  
Steven W. Gorsich ◽  
J. Michael McCaffery ◽  
Janet M. Shaw ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Fission ◽  
Mitochondrial Fusion ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Temperature Sensitive ◽  
Intermembrane Space ◽  
Direct Role ◽  
Membrane Fission ◽  
Mitochondrial Intermembrane Space

Mutations in the dynamin-related GTPase, Mgm1p, have been shown to cause mitochondrial aggregation and mitochondrial DNA loss in Saccharomyces cerevisiae cells, but Mgm1p's exact role in mitochondrial maintenance is unclear. To study the primary function of MGM1, we characterized new temperature sensitive MGM1 alleles. Examination of mitochondrial morphology in mgm1 cells indicates that fragmentation of mitochondrial reticuli is the primary phenotype associated with loss of MGM1 function, with secondary aggregation of mitochondrial fragments. This mgm1 phenotype is identical to that observed in cells with a conditional mutation in FZO1, which encodes a transmembrane GTPase required for mitochondrial fusion, raising the possibility that Mgm1p is also required for fusion. Consistent with this idea, mitochondrial fusion is blocked in mgm1 cells during mating, and deletion of DNM1, which encodes a dynamin-related GTPase required for mitochondrial fission, blocks mitochondrial fragmentation in mgm1 cells. However, in contrast to fzo1 cells, deletion of DNM1 in mgm1 cells restores mitochondrial fusion during mating. This last observation indicates that despite the phenotypic similarities observed between mgm1 and fzo1 cells, MGM1 does not play a direct role in mitochondrial fusion. Although Mgm1p was recently reported to localize to the mitochondrial outer membrane, our studies indicate that Mgm1p is localized to the mitochondrial intermembrane space. Based on our localization data and Mgm1p's structural homology to dynamin, we postulate that it functions in inner membrane remodeling events. In this context, the observed mgm1 phenotypes suggest that inner and outer membrane fission is coupled and that loss of MGM1 function may stimulate Dnm1p-dependent outer membrane fission, resulting in the formation of mitochondrial fragments that are structurally incompetent for fusion.

scholarly journals Appoptosin interacts with mitochondrial outer-membrane fusion proteins and regulates mitochondrial morphology

2016 ◽  
Vol 129 (5) ◽  
pp. 994-1002 ◽  
Author(s):  
Cuilin Zhang ◽  
Zhun Shi ◽  
Lingzhi Zhang ◽  
Zehua Zhou ◽  
Xiaoyuan Zheng ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Outer Membrane ◽  
Fusion Proteins ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Membrane Fusion Proteins

scholarly journals Mdm12p, a Component Required for Mitochondrial Inheritance That Is Conserved between Budding and Fission Yeast

1997 ◽  
Vol 136 (3) ◽  
pp. 545-553 ◽  
Author(s):  
Karen H. Berger ◽  
L. Farah Sogo ◽  
Michael P. Yaffe
Keyword(s):  
Membrane Protein ◽  
Fission Yeast ◽  
Outer Membrane ◽  
Subcellular Fractionation ◽  
Biochemical Properties ◽  
Dominant Negative ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Temperature Sensitive ◽  
Giant Mitochondria

Saccharomyces cerevisiae cells lacking the MDM12 gene product display temperature-sensitive growth and possess abnormally large, round mitochondria that are defective for inheritance by daughter buds. Analysis of the wild-type MDM12 gene revealed its product to be a 31-kD polypeptide that is homologous to a protein of the fission yeast Schizosaccharomyces pombe. When expressed in S. cerevisiae, the S. pombe Mdm12p homolog conferred a dominant-negative phenotype of giant mitochondria and aberrant mitochondrial distribution, suggesting partial functional conservation of Mdm12p activity between budding and fission yeast. The S. cerevisiae Mdm12p was localized by indirect immunofluorescence microscopy and by subcellular fractionation and immunodetection to the mitochondrial outer membrane and displayed biochemical properties of an integral membrane protein. Mdm12p is the third mitochondrial outer membrane protein required for normal mitochondrial morphology and distribution to be identified in S. cerevisiae and the first such mitochondrial component that is conserved between two different species.

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