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Identification of a mitofusin specificity region that confers unique activities to Mfn1 and Mfn2.

ABSTRACT: Mitochondrial structure can be maintained at steady state or modified in response to changes in cellular physiology. This is achieved by the coordinated regulation of dynamic properties including mitochondrial fusion, division, and transport. Disease states, including neurodegeneration, are associated with defects in these processes. In vertebrates, two mitofusin paralogues, Mfn1 and Mfn2, are required for efficient mitochondrial fusion. The mitofusins share a high degree of homology and have very similar domain architecture, including an amino terminal GTPase domain and two extended helical bundles that are connected by flexible regions. Mfn1 and Mfn2 are nonredundant and are both required for mitochondrial outer membrane fusion. However, the molecular features that make these proteins functionally distinct are poorly defined. By engineering chimeric proteins composed of Mfn1 and Mfn2, we discovered a region that contributes to isoform-specific function (mitofusin isoform-specific region [MISR]). MISR confers unique fusion activity and mitofusin-specific nucleotide-dependent assembly properties. We propose that MISR functions in higher-order oligomerization either directly, as an interaction interface, or indirectly through conformational changes.

SUBMITTER: Sloat SR

PROVIDER: S-EPMC6743458 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Identification of a mitofusin specificity region that confers unique activities to Mfn1 and Mfn2.

Sloat S R SR Whitley B N BN Engelhart E A EA Hoppins S S

Molecular biology of the cell 20190612 17

Mitochondrial structure can be maintained at steady state or modified in response to changes in cellular physiology. This is achieved by the coordinated regulation of dynamic properties including mitochondrial fusion, division, and transport. Disease states, including neurodegeneration, are associated with defects in these processes. In vertebrates, two mitofusin paralogues, Mfn1 and Mfn2, are required for efficient mitochondrial fusion. The mitofusins share a high degree of homology and have ve ...[more]

PMID: 31188717

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Project description:Mitochondria alter their shape by undergoing cycles of fusion and fission. Changes in mitochondrial morphology impact on the cellular response to stress, and their interactions with other organelles such as the sarcoplasmic reticulum (SR). Inhibiting mitochondrial fission can protect the heart against acute ischemia/reperfusion (I/R) injury. However, the role of the mitochondrial fusion proteins, Mfn1 and Mfn2, in the response of the adult heart to acute I/R injury is not clear, and is investigated in this study. To determine the effect of combined Mfn1/Mfn2 ablation on the susceptibility to acute myocardial I/R injury, cardiac-specific ablation of both Mfn1 and Mfn2 (DKO) was initiated in mice aged 4-6 weeks, leading to knockout of both these proteins in 8-10-week-old animals. This resulted in fragmented mitochondria (electron microscopy), decreased mitochondrial respiratory function (respirometry), and impaired myocardial contractile function (echocardiography). In DKO mice subjected to in vivo regional myocardial ischemia (30 min) followed by 24 h reperfusion, myocardial infarct size (IS, expressed as a % of the area-at-risk) was reduced by 46% compared with wild-type (WT) hearts. In addition, mitochondria from DKO animals had decreased MPTP opening susceptibility (assessed by Ca(2+)-induced mitochondrial swelling), compared with WT hearts. Mfn2 is a key mediator of mitochondrial/SR tethering, and accordingly, the loss of Mfn2 in DKO hearts reduced the number of interactions measured between these organelles (quantified by proximal ligation assay), attenuated mitochondrial calcium overload (Rhod2 confocal microscopy), and decreased reactive oxygen species production (DCF confocal microscopy) in response to acute I/R injury. No differences in isolated mitochondrial ROS emissions (Amplex Red) were detected in response to Ca(2+) and Antimycin A, further implicating disruption of mitochondria/SR tethering as the protective mechanism. In summary, despite apparent mitochondrial dysfunction, hearts deficient in both Mfn1 and Mfn2 are protected against acute myocardial infarction due to impaired mitochondria/SR tethering.

Dataset Information

Identification of a mitofusin specificity region that confers unique activities to Mfn1 and Mfn2.

Publications

Identification of a mitofusin specificity region that confers unique activities to Mfn1 and Mfn2.

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