Limits...
Mdv1p is a WD repeat protein that interacts with the dynamin-related GTPase, Dnm1p, to trigger mitochondrial division.

Tieu Q, Nunnari J - J. Cell Biol. (2000)

Bottom Line: Whereas localization of Mdv1p to these structures requires Dnm1p, localization of Mdv1p to mitochondrial membranes does not.Dnm1p-independent targeting of Mdv1p to mitochondria requires MDV2.Our data indicate that MDV2 also functions separately to regulate the assembly of Dnm1p into punctate structures.

View Article: PubMed Central - PubMed

Affiliation: Section of Molecular and Cellular Biology, University of California Davis, Davis, California 95616, USA.

ABSTRACT
Mitochondrial fission is mediated by the dynamin-related GTPase, Dnm1p, which assembles on the mitochondrial outer membrane into punctate structures associated with sites of membrane constriction and fission. We have identified additional nuclear genes required for mitochondrial fission, termed MDV (for mitochondrial division). MDV1 encodes a predicted soluble protein, containing a coiled-coil motif and seven COOH-terminal WD repeats. Genetic and two-hybrid analyses indicate that Mdv1p interacts with Dnm1p to mediate mitochondrial fission. In addition, Mdv1p colocalizes with Dnm1p in fission-mediating punctate structures on the mitochondrial outer membrane. Whereas localization of Mdv1p to these structures requires Dnm1p, localization of Mdv1p to mitochondrial membranes does not. This indicates that Mdv1p possesses a Dnm1p-independent mitochondrial targeting signal. Dnm1p-independent targeting of Mdv1p to mitochondria requires MDV2. Our data indicate that MDV2 also functions separately to regulate the assembly of Dnm1p into punctate structures. In contrast, Mdv1p is not required for the assembly of Dnm1p, but Dnm1p-containing punctate structures lacking Mdv1p are not able to complete division. Our studies suggest that mitochondrial fission is a multi-step process in which Mdv2p regulates the assembly of Dnm1p into punctate structures and together with Mdv1p functions later during fission to facilitate Dnm1p-dependent mitochondrial membrane constriction and/or division.

Show MeSH

Related in: MedlinePlus

Mutations in MDV genes suppress mitochondrial fragmentation in fzo1-1 cells and cause mitochondrial membranes to form net-like structures. Mito-GFP was used to visualize mitochondrial morphology. All strains were grown at 25°C to log phase and imaged at 25°C, or after shifting to 37°C for 1 h. A, Mitochondrial morphology in fzo1-1 mdv double mutants. B, Mitochondrial morphology in mdv single mutants. Bars, 2 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2192646&req=5

Figure 2: Mutations in MDV genes suppress mitochondrial fragmentation in fzo1-1 cells and cause mitochondrial membranes to form net-like structures. Mito-GFP was used to visualize mitochondrial morphology. All strains were grown at 25°C to log phase and imaged at 25°C, or after shifting to 37°C for 1 h. A, Mitochondrial morphology in fzo1-1 mdv double mutants. B, Mitochondrial morphology in mdv single mutants. Bars, 2 μm.

Mentions: Several observations indicate that MDV1 and MDV2 function in mitochondrial fission. First, by examining mitochondrial morphology in mdv fzo1-1 cells, we determined that mutations in both MDV1 and MDV2 block mitochondrial fragmentation (Fig. 2 A and 3). Specifically, mitochondrial net-like structures are observed in mdv fzo1-1 cells grown at either permissive or nonpermissive temperature (Fig. 2 A and 3). These structures are also observed in mdv1-1 and mdv2-1 single mutant cells, consistent with the fact that these mutations suppress fzo1 phenotypes by bypassing FZO1 function (Fig. 2 B and 3). Mitochondrial net structures have been previously reported to occur in Δdnm1 cells (Bleazard et al. 1999). These structures likely arise when mitochondrial ends fuse with tubule sides and, because fission is blocked, new tubule ends cannot be generated. Mitochondrial net structures also are observed in Δdnm1 fzo1-1 cells under conditions where a block in mitochondrial fission precedes a block in fusion (Bleazard et al. 1999). Interestingly, mitochondrial nets are observed in double Δdnm1 mdv mutant cells, suggesting that these genes act in the same or in parallel pathways (not shown). Thus, the phenotypic characteristics of mdv cells are identical to those observed in Δdnm1 cells, suggesting that the MDV genes act together with DNM1 to mediate mitochondrial fission.


Mdv1p is a WD repeat protein that interacts with the dynamin-related GTPase, Dnm1p, to trigger mitochondrial division.

Tieu Q, Nunnari J - J. Cell Biol. (2000)

Mutations in MDV genes suppress mitochondrial fragmentation in fzo1-1 cells and cause mitochondrial membranes to form net-like structures. Mito-GFP was used to visualize mitochondrial morphology. All strains were grown at 25°C to log phase and imaged at 25°C, or after shifting to 37°C for 1 h. A, Mitochondrial morphology in fzo1-1 mdv double mutants. B, Mitochondrial morphology in mdv single mutants. Bars, 2 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2192646&req=5

Figure 2: Mutations in MDV genes suppress mitochondrial fragmentation in fzo1-1 cells and cause mitochondrial membranes to form net-like structures. Mito-GFP was used to visualize mitochondrial morphology. All strains were grown at 25°C to log phase and imaged at 25°C, or after shifting to 37°C for 1 h. A, Mitochondrial morphology in fzo1-1 mdv double mutants. B, Mitochondrial morphology in mdv single mutants. Bars, 2 μm.
Mentions: Several observations indicate that MDV1 and MDV2 function in mitochondrial fission. First, by examining mitochondrial morphology in mdv fzo1-1 cells, we determined that mutations in both MDV1 and MDV2 block mitochondrial fragmentation (Fig. 2 A and 3). Specifically, mitochondrial net-like structures are observed in mdv fzo1-1 cells grown at either permissive or nonpermissive temperature (Fig. 2 A and 3). These structures are also observed in mdv1-1 and mdv2-1 single mutant cells, consistent with the fact that these mutations suppress fzo1 phenotypes by bypassing FZO1 function (Fig. 2 B and 3). Mitochondrial net structures have been previously reported to occur in Δdnm1 cells (Bleazard et al. 1999). These structures likely arise when mitochondrial ends fuse with tubule sides and, because fission is blocked, new tubule ends cannot be generated. Mitochondrial net structures also are observed in Δdnm1 fzo1-1 cells under conditions where a block in mitochondrial fission precedes a block in fusion (Bleazard et al. 1999). Interestingly, mitochondrial nets are observed in double Δdnm1 mdv mutant cells, suggesting that these genes act in the same or in parallel pathways (not shown). Thus, the phenotypic characteristics of mdv cells are identical to those observed in Δdnm1 cells, suggesting that the MDV genes act together with DNM1 to mediate mitochondrial fission.

Bottom Line: Whereas localization of Mdv1p to these structures requires Dnm1p, localization of Mdv1p to mitochondrial membranes does not.Dnm1p-independent targeting of Mdv1p to mitochondria requires MDV2.Our data indicate that MDV2 also functions separately to regulate the assembly of Dnm1p into punctate structures.

View Article: PubMed Central - PubMed

Affiliation: Section of Molecular and Cellular Biology, University of California Davis, Davis, California 95616, USA.

ABSTRACT
Mitochondrial fission is mediated by the dynamin-related GTPase, Dnm1p, which assembles on the mitochondrial outer membrane into punctate structures associated with sites of membrane constriction and fission. We have identified additional nuclear genes required for mitochondrial fission, termed MDV (for mitochondrial division). MDV1 encodes a predicted soluble protein, containing a coiled-coil motif and seven COOH-terminal WD repeats. Genetic and two-hybrid analyses indicate that Mdv1p interacts with Dnm1p to mediate mitochondrial fission. In addition, Mdv1p colocalizes with Dnm1p in fission-mediating punctate structures on the mitochondrial outer membrane. Whereas localization of Mdv1p to these structures requires Dnm1p, localization of Mdv1p to mitochondrial membranes does not. This indicates that Mdv1p possesses a Dnm1p-independent mitochondrial targeting signal. Dnm1p-independent targeting of Mdv1p to mitochondria requires MDV2. Our data indicate that MDV2 also functions separately to regulate the assembly of Dnm1p into punctate structures. In contrast, Mdv1p is not required for the assembly of Dnm1p, but Dnm1p-containing punctate structures lacking Mdv1p are not able to complete division. Our studies suggest that mitochondrial fission is a multi-step process in which Mdv2p regulates the assembly of Dnm1p into punctate structures and together with Mdv1p functions later during fission to facilitate Dnm1p-dependent mitochondrial membrane constriction and/or division.

Show MeSH
Related in: MedlinePlus