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The role of Fis1p-Mdv1p interactions in mitochondrial fission complex assembly.

Karren MA, Coonrod EM, Anderson TK, Shaw JM - J. Cell Biol. (2005)

Bottom Line: Furthermore, we show that conditional mutations in the Fis1p TPR-like domain cause fission complex assembly defects that are suppressed by mutations in the Mdv1p-predicted coiled coil.We also define separable functions for the Fis1p NH(2)-terminal arm and TPR-like fold.These studies suggest that the concave binding surface of the Fis1p TPR-like fold interacts with Mdv1p during mitochondrial fission and that Mdv1p facilitates Dnm1p recruitment into functional fission complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.

ABSTRACT
Mitochondrial division requires coordinated interactions among Fis1p, Mdv1p, and the Dnm1p GTPase, which assemble into fission complexes on the outer mitochondrial membrane. The integral outer membrane protein Fis1p contains a cytoplasmic domain consisting of a tetratricopeptide repeat (TPR)-like fold and a short NH(2)-terminal helix. Although it is known that the cytoplasmic domain is necessary for assembly of Mdv1p and Dnm1p into fission complexes, the molecular details of this assembly are not clear. In this study, we provide new evidence that the Fis1p-Mdv1p interaction is direct. Furthermore, we show that conditional mutations in the Fis1p TPR-like domain cause fission complex assembly defects that are suppressed by mutations in the Mdv1p-predicted coiled coil. We also define separable functions for the Fis1p NH(2)-terminal arm and TPR-like fold. These studies suggest that the concave binding surface of the Fis1p TPR-like fold interacts with Mdv1p during mitochondrial fission and that Mdv1p facilitates Dnm1p recruitment into functional fission complexes.

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The Mdv1E250Gp mutation suppresses the temperature-sensitive Fis1-3p fission defect. (A) Schematic representation of Mdv1p, with the positions of the predicted coiled coil (CC), WD-repeat region, and E250G substitution indicated. (B) Growth phenotypes of indicated strains (800 cells per spot) grown on S-glycerol selective media at either 25 or 37°C. Fission is disrupted (indicated by growth) at 37°C in fzo1-1 fis1-3 cells expressing plasmid-borne Mdv1p (middle). Fission is restored (indicated by no growth) at 37°C in fzo1-1 fis1-3 cells expressing plasmid-borne Mdv1E250Gp (bottom), similar to fzo1-1 cells (top). (C) Quantification of mitochondrial morphology (n ≥ 300, SDs are indicated) in strains grown at 25 or 37°C.
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fig4: The Mdv1E250Gp mutation suppresses the temperature-sensitive Fis1-3p fission defect. (A) Schematic representation of Mdv1p, with the positions of the predicted coiled coil (CC), WD-repeat region, and E250G substitution indicated. (B) Growth phenotypes of indicated strains (800 cells per spot) grown on S-glycerol selective media at either 25 or 37°C. Fission is disrupted (indicated by growth) at 37°C in fzo1-1 fis1-3 cells expressing plasmid-borne Mdv1p (middle). Fission is restored (indicated by no growth) at 37°C in fzo1-1 fis1-3 cells expressing plasmid-borne Mdv1E250Gp (bottom), similar to fzo1-1 cells (top). (C) Quantification of mitochondrial morphology (n ≥ 300, SDs are indicated) in strains grown at 25 or 37°C.

Mentions: We screened for suppressor mutations in either Dnm1p or Mdv1p that rescued mitochondrial fission defects at 37°C (see Materials and methods). At the time of submission, we had identified no dnm1 alleles that suppressed fis1-3 phenotypes. However, we identified several robust suppressor alleles that altered residues in MDV1. These suppressor mutations are located in or immediately upstream of the MDV1 predicted coiled-coil–forming domain. One of these, mdv1E250G (Fig. 4 A), was characterized in detail.


The role of Fis1p-Mdv1p interactions in mitochondrial fission complex assembly.

Karren MA, Coonrod EM, Anderson TK, Shaw JM - J. Cell Biol. (2005)

The Mdv1E250Gp mutation suppresses the temperature-sensitive Fis1-3p fission defect. (A) Schematic representation of Mdv1p, with the positions of the predicted coiled coil (CC), WD-repeat region, and E250G substitution indicated. (B) Growth phenotypes of indicated strains (800 cells per spot) grown on S-glycerol selective media at either 25 or 37°C. Fission is disrupted (indicated by growth) at 37°C in fzo1-1 fis1-3 cells expressing plasmid-borne Mdv1p (middle). Fission is restored (indicated by no growth) at 37°C in fzo1-1 fis1-3 cells expressing plasmid-borne Mdv1E250Gp (bottom), similar to fzo1-1 cells (top). (C) Quantification of mitochondrial morphology (n ≥ 300, SDs are indicated) in strains grown at 25 or 37°C.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171191&req=5

fig4: The Mdv1E250Gp mutation suppresses the temperature-sensitive Fis1-3p fission defect. (A) Schematic representation of Mdv1p, with the positions of the predicted coiled coil (CC), WD-repeat region, and E250G substitution indicated. (B) Growth phenotypes of indicated strains (800 cells per spot) grown on S-glycerol selective media at either 25 or 37°C. Fission is disrupted (indicated by growth) at 37°C in fzo1-1 fis1-3 cells expressing plasmid-borne Mdv1p (middle). Fission is restored (indicated by no growth) at 37°C in fzo1-1 fis1-3 cells expressing plasmid-borne Mdv1E250Gp (bottom), similar to fzo1-1 cells (top). (C) Quantification of mitochondrial morphology (n ≥ 300, SDs are indicated) in strains grown at 25 or 37°C.
Mentions: We screened for suppressor mutations in either Dnm1p or Mdv1p that rescued mitochondrial fission defects at 37°C (see Materials and methods). At the time of submission, we had identified no dnm1 alleles that suppressed fis1-3 phenotypes. However, we identified several robust suppressor alleles that altered residues in MDV1. These suppressor mutations are located in or immediately upstream of the MDV1 predicted coiled-coil–forming domain. One of these, mdv1E250G (Fig. 4 A), was characterized in detail.

Bottom Line: Furthermore, we show that conditional mutations in the Fis1p TPR-like domain cause fission complex assembly defects that are suppressed by mutations in the Mdv1p-predicted coiled coil.We also define separable functions for the Fis1p NH(2)-terminal arm and TPR-like fold.These studies suggest that the concave binding surface of the Fis1p TPR-like fold interacts with Mdv1p during mitochondrial fission and that Mdv1p facilitates Dnm1p recruitment into functional fission complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.

ABSTRACT
Mitochondrial division requires coordinated interactions among Fis1p, Mdv1p, and the Dnm1p GTPase, which assemble into fission complexes on the outer mitochondrial membrane. The integral outer membrane protein Fis1p contains a cytoplasmic domain consisting of a tetratricopeptide repeat (TPR)-like fold and a short NH(2)-terminal helix. Although it is known that the cytoplasmic domain is necessary for assembly of Mdv1p and Dnm1p into fission complexes, the molecular details of this assembly are not clear. In this study, we provide new evidence that the Fis1p-Mdv1p interaction is direct. Furthermore, we show that conditional mutations in the Fis1p TPR-like domain cause fission complex assembly defects that are suppressed by mutations in the Mdv1p-predicted coiled coil. We also define separable functions for the Fis1p NH(2)-terminal arm and TPR-like fold. These studies suggest that the concave binding surface of the Fis1p TPR-like fold interacts with Mdv1p during mitochondrial fission and that Mdv1p facilitates Dnm1p recruitment into functional fission complexes.

Show MeSH
Related in: MedlinePlus