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A mitochondrial-focused genetic interaction map reveals a scaffold-like complex required for inner membrane organization in mitochondria.

Hoppins S, Collins SR, Cassidy-Stone A, Hummel E, Devay RM, Lackner LL, Westermann B, Schuldiner M, Weissman JS, Nunnari J - J. Cell Biol. (2011)

Bottom Line: The MITO-MAP also reveals a large inner membrane-associated complex, which we term MitOS for mitochondrial organizing structure, comprised of Fcj1/Mitofilin, a conserved inner membrane protein, and five additional components.We show that MitOS acts in concert with ATP synthase dimers to organize the inner membrane and promote normal mitochondrial morphology.We propose that MitOS acts as a conserved mitochondrial skeletal structure that differentiates regions of the inner membrane to establish the normal internal architecture of mitochondria.

View Article: PubMed Central - HTML - PubMed

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

ABSTRACT
To broadly explore mitochondrial structure and function as well as the communication of mitochondria with other cellular pathways, we constructed a quantitative, high-density genetic interaction map (the MITO-MAP) in Saccharomyces cerevisiae. The MITO-MAP provides a comprehensive view of mitochondrial function including insights into the activity of uncharacterized mitochondrial proteins and the functional connection between mitochondria and the ER. The MITO-MAP also reveals a large inner membrane-associated complex, which we term MitOS for mitochondrial organizing structure, comprised of Fcj1/Mitofilin, a conserved inner membrane protein, and five additional components. MitOS physically and functionally interacts with both outer and inner membrane components and localizes to extended structures that wrap around the inner membrane. We show that MitOS acts in concert with ATP synthase dimers to organize the inner membrane and promote normal mitochondrial morphology. We propose that MitOS acts as a conserved mitochondrial skeletal structure that differentiates regions of the inner membrane to establish the normal internal architecture of mitochondria.

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MitOS is a conserved mitochondrial inner membrane–associated complex. (A) Schematic representation of predicted structural features of MitOS components. As described in Materials and methods, the amino acid sequences of MitOS components were subject to bioinformatic analyses to identify conserved features. Fcj1 contains a conserved Mitofilin domain, Mos1 contains a conserved eukaryotic DUF, and Aim37 and Mos2 are both similar to apolipoproteins, predicted to form extended amphipathic α helices (Lamant et al., 2006). Aim13 contains a conserved fungal-specific DUF and a CHCHD-like motif in its C-terminal region, which is marked by two conserved cysteine residues (Cavallaro, 2010). Significantly, a human CHCHD3 protein was reported to be in a complex with Mitofilin isolated from human heart mitochondria (Xie et al., 2007). (B) Protease protection analysis of mitochondria isolated from strains expressing FLAG-tagged versions of MitOS components. Intact mitochondria (lanes 1 and 4), mitoplasts (lane 3), or solubilized mitochondria (lane 2) before treatment with (+) or without (−) trypsin were analyzed by SDS-PAGE and immunoblotting with the indicated antisera. (C) Separation of soluble and membrane proteins by alkaline extraction. Mitochondria were treated with 0.1 M NaCO3 and centrifuged into pellet (P) and soluble (S) fractions, which were analyzed by SDS-PAGE and immunoblotting with the indicated anti-sera. T, total.
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fig4: MitOS is a conserved mitochondrial inner membrane–associated complex. (A) Schematic representation of predicted structural features of MitOS components. As described in Materials and methods, the amino acid sequences of MitOS components were subject to bioinformatic analyses to identify conserved features. Fcj1 contains a conserved Mitofilin domain, Mos1 contains a conserved eukaryotic DUF, and Aim37 and Mos2 are both similar to apolipoproteins, predicted to form extended amphipathic α helices (Lamant et al., 2006). Aim13 contains a conserved fungal-specific DUF and a CHCHD-like motif in its C-terminal region, which is marked by two conserved cysteine residues (Cavallaro, 2010). Significantly, a human CHCHD3 protein was reported to be in a complex with Mitofilin isolated from human heart mitochondria (Xie et al., 2007). (B) Protease protection analysis of mitochondria isolated from strains expressing FLAG-tagged versions of MitOS components. Intact mitochondria (lanes 1 and 4), mitoplasts (lane 3), or solubilized mitochondria (lane 2) before treatment with (+) or without (−) trypsin were analyzed by SDS-PAGE and immunoblotting with the indicated antisera. (C) Separation of soluble and membrane proteins by alkaline extraction. Mitochondria were treated with 0.1 M NaCO3 and centrifuged into pellet (P) and soluble (S) fractions, which were analyzed by SDS-PAGE and immunoblotting with the indicated anti-sera. T, total.

Mentions: Bioinformatic analysis indicated that with the exception of Aim13, MitOS components possess hydrophobic regions, which suggests that they are integral membrane proteins (Fig. 4 A). Fcj1, Aim13, Aim37, and Mos2 also possess regions predicted to form coiled coil structures, which is possibly important for formation of the MitOS complex. Although Aim5 is likely to be fungal specific, all other MitOS components are conserved or possess predicted conserved features (Fig. 4 A). Thus, the structure and function of MitOS is likely conserved.


A mitochondrial-focused genetic interaction map reveals a scaffold-like complex required for inner membrane organization in mitochondria.

Hoppins S, Collins SR, Cassidy-Stone A, Hummel E, Devay RM, Lackner LL, Westermann B, Schuldiner M, Weissman JS, Nunnari J - J. Cell Biol. (2011)

MitOS is a conserved mitochondrial inner membrane–associated complex. (A) Schematic representation of predicted structural features of MitOS components. As described in Materials and methods, the amino acid sequences of MitOS components were subject to bioinformatic analyses to identify conserved features. Fcj1 contains a conserved Mitofilin domain, Mos1 contains a conserved eukaryotic DUF, and Aim37 and Mos2 are both similar to apolipoproteins, predicted to form extended amphipathic α helices (Lamant et al., 2006). Aim13 contains a conserved fungal-specific DUF and a CHCHD-like motif in its C-terminal region, which is marked by two conserved cysteine residues (Cavallaro, 2010). Significantly, a human CHCHD3 protein was reported to be in a complex with Mitofilin isolated from human heart mitochondria (Xie et al., 2007). (B) Protease protection analysis of mitochondria isolated from strains expressing FLAG-tagged versions of MitOS components. Intact mitochondria (lanes 1 and 4), mitoplasts (lane 3), or solubilized mitochondria (lane 2) before treatment with (+) or without (−) trypsin were analyzed by SDS-PAGE and immunoblotting with the indicated antisera. (C) Separation of soluble and membrane proteins by alkaline extraction. Mitochondria were treated with 0.1 M NaCO3 and centrifuged into pellet (P) and soluble (S) fractions, which were analyzed by SDS-PAGE and immunoblotting with the indicated anti-sera. T, total.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3198156&req=5

fig4: MitOS is a conserved mitochondrial inner membrane–associated complex. (A) Schematic representation of predicted structural features of MitOS components. As described in Materials and methods, the amino acid sequences of MitOS components were subject to bioinformatic analyses to identify conserved features. Fcj1 contains a conserved Mitofilin domain, Mos1 contains a conserved eukaryotic DUF, and Aim37 and Mos2 are both similar to apolipoproteins, predicted to form extended amphipathic α helices (Lamant et al., 2006). Aim13 contains a conserved fungal-specific DUF and a CHCHD-like motif in its C-terminal region, which is marked by two conserved cysteine residues (Cavallaro, 2010). Significantly, a human CHCHD3 protein was reported to be in a complex with Mitofilin isolated from human heart mitochondria (Xie et al., 2007). (B) Protease protection analysis of mitochondria isolated from strains expressing FLAG-tagged versions of MitOS components. Intact mitochondria (lanes 1 and 4), mitoplasts (lane 3), or solubilized mitochondria (lane 2) before treatment with (+) or without (−) trypsin were analyzed by SDS-PAGE and immunoblotting with the indicated antisera. (C) Separation of soluble and membrane proteins by alkaline extraction. Mitochondria were treated with 0.1 M NaCO3 and centrifuged into pellet (P) and soluble (S) fractions, which were analyzed by SDS-PAGE and immunoblotting with the indicated anti-sera. T, total.
Mentions: Bioinformatic analysis indicated that with the exception of Aim13, MitOS components possess hydrophobic regions, which suggests that they are integral membrane proteins (Fig. 4 A). Fcj1, Aim13, Aim37, and Mos2 also possess regions predicted to form coiled coil structures, which is possibly important for formation of the MitOS complex. Although Aim5 is likely to be fungal specific, all other MitOS components are conserved or possess predicted conserved features (Fig. 4 A). Thus, the structure and function of MitOS is likely conserved.

Bottom Line: The MITO-MAP also reveals a large inner membrane-associated complex, which we term MitOS for mitochondrial organizing structure, comprised of Fcj1/Mitofilin, a conserved inner membrane protein, and five additional components.We show that MitOS acts in concert with ATP synthase dimers to organize the inner membrane and promote normal mitochondrial morphology.We propose that MitOS acts as a conserved mitochondrial skeletal structure that differentiates regions of the inner membrane to establish the normal internal architecture of mitochondria.

View Article: PubMed Central - HTML - PubMed

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

ABSTRACT
To broadly explore mitochondrial structure and function as well as the communication of mitochondria with other cellular pathways, we constructed a quantitative, high-density genetic interaction map (the MITO-MAP) in Saccharomyces cerevisiae. The MITO-MAP provides a comprehensive view of mitochondrial function including insights into the activity of uncharacterized mitochondrial proteins and the functional connection between mitochondria and the ER. The MITO-MAP also reveals a large inner membrane-associated complex, which we term MitOS for mitochondrial organizing structure, comprised of Fcj1/Mitofilin, a conserved inner membrane protein, and five additional components. MitOS physically and functionally interacts with both outer and inner membrane components and localizes to extended structures that wrap around the inner membrane. We show that MitOS acts in concert with ATP synthase dimers to organize the inner membrane and promote normal mitochondrial morphology. We propose that MitOS acts as a conserved mitochondrial skeletal structure that differentiates regions of the inner membrane to establish the normal internal architecture of mitochondria.

Show MeSH
Related in: MedlinePlus