Mitochondria dynamically fuse and divide within cells, and the proper balance of fusion and fission is necessary for normal mitochondrial function, morphology, and distribution. Drp1 is a dynamin-related GTPase required for mitochondrial fission in mammalian cells. It harbors four distinct domains: GTP-binding, middle, insert B, and GTPase effector. A lethal mutation (A395D) within the Drp1 middle domain was reported in a neonate with microcephaly, abnormal brain development, optic atrophy, and lactic acidemia (Waterham, H. R., Koster, J., van Roermund, C. W., Mooyer, P. A., Wanders, R. J., and Leonard, J. V. (2007) N. Engl. J. Med. 356, 1736–1741). Mitochondria within patient-derived fibroblasts were markedly elongated, but the molecular mechanisms underlying these findings were not demonstrated. Because the middle domain is particularly important for the self-assembly of some dynamin superfamily proteins, we tested the hypothesis that this A395D mutation, and two other middle domain mutations (G350D, G363D) were important for Drp1 tetramerization, higher order assembly, and function. Although tetramerization appeared largely intact, each of these mutations compromised higher order assembly and assembly-dependent stimulation of Drp1 GTPase activity. Moreover, mutant Drp1 proteins exhibited impaired localization to mitochondria, indicating that this higher order assembly is important for mitochondrial recruitment, retention, or both. Overexpression of these middle domain mutants markedly inhibited mitochondrial division in cells. Thus, the Drp1 A395D lethal defect likely resulted in impaired higher order assembly of Drp1 at mitochondria, leading to decreased fission, elongated mitochondria, and altered cellular distribution of mitochondria. Mitochondria dynamically fuse and divide within cells, and the proper balance of fusion and fission is necessary for normal mitochondrial function, morphology, and distribution. Drp1 is a dynamin-related GTPase required for mitochondrial fission in mammalian cells. It harbors four distinct domains: GTP-binding, middle, insert B, and GTPase effector. A lethal mutation (A395D) within the Drp1 middle domain was reported in a neonate with microcephaly, abnormal brain development, optic atrophy, and lactic acidemia (Waterham, H. R., Koster, J., van Roermund, C. W., Mooyer, P. A., Wanders, R. J., and Leonard, J. V. (2007) N. Engl. J. Med. 356, 1736–1741). Mitochondria within patient-derived fibroblasts were markedly elongated, but the molecular mechanisms underlying these findings were not demonstrated. Because the middle domain is particularly important for the self-assembly of some dynamin superfamily proteins, we tested the hypothesis that this A395D mutation, and two other middle domain mutations (G350D, G363D) were important for Drp1 tetramerization, higher order assembly, and function. Although tetramerization appeared largely intact, each of these mutations compromised higher order assembly and assembly-dependent stimulation of Drp1 GTPase activity. Moreover, mutant Drp1 proteins exhibited impaired localization to mitochondria, indicating that this higher order assembly is important for mitochondrial recruitment, retention, or both. Overexpression of these middle domain mutants markedly inhibited mitochondrial division in cells. Thus, the Drp1 A395D lethal defect likely resulted in impaired higher order assembly of Drp1 at mitochondria, leading to decreased fission, elongated mitochondria, and altered cellular distribution of mitochondria.
Journal Article The Effects of Nonclassic Pediatric Bacterial Pathogens on the Usefulness of the Directigen Latex Agglutination Test Get access Robert B. Hill, MD, Robert B. Hill, MD 1 From the Department of Pathology and Area Laboratory Services, Tripler AMC, Hawaii. Search for other works by this author on: Oxford Academic Google Scholar Stephen Adams, DO, Stephen Adams, DO 1 From the Department of Pathology and Area Laboratory Services, Tripler AMC, Hawaii. Search for other works by this author on: Oxford Academic Google Scholar Bruce A. Gunn, PhD, Bruce A. Gunn, PhD 2 Bureau of Nutrition Services, Texas Department of Health, Austin, Texas. Search for other works by this author on: Oxford Academic Google Scholar Bardwell J. Eberly, M(ASCP)SM Bardwell J. Eberly, M(ASCP)SM 1 From the Department of Pathology and Area Laboratory Services, Tripler AMC, Hawaii. Search for other works by this author on: Oxford Academic Google Scholar American Journal of Clinical Pathology, Volume 101, Issue 6, 1 June 1994, Pages 729–732, https://doi.org/10.1093/ajcp/101.6.729 Published: 01 June 1994 Article history Received: 20 January 1993 Accepted: 09 June 1993 Published: 01 June 1994
Fis1bindsdirectlytoDnm1andtoMdv1.TwoFis1regionshavebeenpreviouslyimplicatedinMdv1recruitment:anN-ter-minal “arm” and a concave surface formed by evolutionarilyconservedresiduesinthetetratricopeptiderepeatdomain.Per-turbing either Fis1 region does not affect Mdv1 binding, butbothregionsinfluenceDnm1binding.Fis1lackingitsN-termi-nal arm binds tightly to Dnm1, and binding is abolished bymutationstotheFis1concavesurface.TheFis1-Dnm1interac-tion decreases more than 100-fold in the presence of the Fis1arm, suggesting that the arm acts in an autoinhibitory man-ner to restrict access to the Dnm1 binding site on Fis1. Ourdata indicate that the concave surface of the Fis1 tetratri-copeptide repeat-like domain is evolutionarily conserved tobindthedynamin-likeGTPaseDnm1andnotMdv1asprevi-ously predicted.
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