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Yeast Miro GTPase, Gem1p, regulates mitochondrial morphology via a novel pathway.

Frederick RL, McCaffery JM, Cunningham KW, Okamoto K, Shaw JM - J. Cell Biol. (2004)

Bottom Line: Biol.Chem. 278:6495-6502), Gem1p is not required for pheromone-induced yeast cell death.Thus, Gem1p defines a novel mitochondrial morphology pathway which may integrate cell signaling events with mitochondrial dynamics.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.

ABSTRACT
Cell signaling events elicit changes in mitochondrial shape and activity. However, few mitochondrial proteins that interact with signaling pathways have been identified. Candidates include the conserved mitochondrial Rho (Miro) family of proteins, which contain two GTPase domains flanking a pair of calcium-binding EF-hand motifs. We show that Gem1p (yeast Miro; encoded by YAL048C) is a tail-anchored outer mitochondrial membrane protein. Cells lacking Gem1p contain collapsed, globular, or grape-like mitochondria. We demonstrate that Gem1p is not an essential component of characterized pathways that regulate mitochondrial dynamics. Genetic studies indicate both GTPase domains and EF-hand motifs, which are exposed to the cytoplasm, are required for Gem1p function. Although overexpression of a mutant human Miro protein caused increased apoptotic activity in cultured cells (Fransson et al., 2003. J. Biol. Chem. 278:6495-6502), Gem1p is not required for pheromone-induced yeast cell death. Thus, Gem1p defines a novel mitochondrial morphology pathway which may integrate cell signaling events with mitochondrial dynamics.

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The COOH-terminal 45 aa of Gem1p are sufficient for mitochondrial targeting. Images of GEM1 cells (JSY7000) expressing GFP alone (A–D) or GFP-Gem1p (aa618-662) (E–H) are shown. Mitochondria were visualized simultaneously with mito-RFP. v, vacuole. Bar, 5 μm.
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fig8: The COOH-terminal 45 aa of Gem1p are sufficient for mitochondrial targeting. Images of GEM1 cells (JSY7000) expressing GFP alone (A–D) or GFP-Gem1p (aa618-662) (E–H) are shown. Mitochondria were visualized simultaneously with mito-RFP. v, vacuole. Bar, 5 μm.

Mentions: To confirm that Gem1p behaves like a tail-anchored protein, we verified that the COOH-terminal 45 aa of Gem1p were sufficient to localize GFP to mitochondria (Fig. 8, E–H). When GFP was fused to residues 618–662 of Gem1p, GFP-associated fluorescence completely overlapped with mito-RFP-labeled mitochondria. In a control experiment, GFP expressed in wild-type cells localized to the cytoplasm with visible exclusion from the vacuole (Fig. 8, A–D). GFP-Gem1p lacking amino acids 618–662 was found in the cytoplasm (unpublished data), indicating that the COOH terminus is required for targeting. Because amino acids 633–652 are hydrophobic and predicted to span the membrane as a single α-helix (Fig. 1 D), this topology would place the COOH-terminal 10 aa of Gem1p in the intermembrane space.


Yeast Miro GTPase, Gem1p, regulates mitochondrial morphology via a novel pathway.

Frederick RL, McCaffery JM, Cunningham KW, Okamoto K, Shaw JM - J. Cell Biol. (2004)

The COOH-terminal 45 aa of Gem1p are sufficient for mitochondrial targeting. Images of GEM1 cells (JSY7000) expressing GFP alone (A–D) or GFP-Gem1p (aa618-662) (E–H) are shown. Mitochondria were visualized simultaneously with mito-RFP. v, vacuole. Bar, 5 μm.
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Related In: Results  -  Collection

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fig8: The COOH-terminal 45 aa of Gem1p are sufficient for mitochondrial targeting. Images of GEM1 cells (JSY7000) expressing GFP alone (A–D) or GFP-Gem1p (aa618-662) (E–H) are shown. Mitochondria were visualized simultaneously with mito-RFP. v, vacuole. Bar, 5 μm.
Mentions: To confirm that Gem1p behaves like a tail-anchored protein, we verified that the COOH-terminal 45 aa of Gem1p were sufficient to localize GFP to mitochondria (Fig. 8, E–H). When GFP was fused to residues 618–662 of Gem1p, GFP-associated fluorescence completely overlapped with mito-RFP-labeled mitochondria. In a control experiment, GFP expressed in wild-type cells localized to the cytoplasm with visible exclusion from the vacuole (Fig. 8, A–D). GFP-Gem1p lacking amino acids 618–662 was found in the cytoplasm (unpublished data), indicating that the COOH terminus is required for targeting. Because amino acids 633–652 are hydrophobic and predicted to span the membrane as a single α-helix (Fig. 1 D), this topology would place the COOH-terminal 10 aa of Gem1p in the intermembrane space.

Bottom Line: Biol.Chem. 278:6495-6502), Gem1p is not required for pheromone-induced yeast cell death.Thus, Gem1p defines a novel mitochondrial morphology pathway which may integrate cell signaling events with mitochondrial dynamics.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.

ABSTRACT
Cell signaling events elicit changes in mitochondrial shape and activity. However, few mitochondrial proteins that interact with signaling pathways have been identified. Candidates include the conserved mitochondrial Rho (Miro) family of proteins, which contain two GTPase domains flanking a pair of calcium-binding EF-hand motifs. We show that Gem1p (yeast Miro; encoded by YAL048C) is a tail-anchored outer mitochondrial membrane protein. Cells lacking Gem1p contain collapsed, globular, or grape-like mitochondria. We demonstrate that Gem1p is not an essential component of characterized pathways that regulate mitochondrial dynamics. Genetic studies indicate both GTPase domains and EF-hand motifs, which are exposed to the cytoplasm, are required for Gem1p function. Although overexpression of a mutant human Miro protein caused increased apoptotic activity in cultured cells (Fransson et al., 2003. J. Biol. Chem. 278:6495-6502), Gem1p is not required for pheromone-induced yeast cell death. Thus, Gem1p defines a novel mitochondrial morphology pathway which may integrate cell signaling events with mitochondrial dynamics.

Show MeSH