title: Miro's N-terminal GTPase domain is required for transport of mitochondria into axons and dendrites.
abstract: Mitochondria are dynamically transported in and out of neuronal processes to maintain neuronal excitability and synaptic function. In higher eukaryotes, the mitochondrial GTPase Miro binds Milton/TRAK adaptor proteins linking microtubule motors to mitochondria. Here we show that Drosophila Miro (dMiro), which has previously been shown to be required for kinesin-driven axonal transport, is also critically required for the dynein-driven distribution of mitochondria into dendrites. In addition, we used the loss-of-function mutations dMiroT25N and dMiroT460N to determine the significance of dMiro's N-terminal and C-terminal GTPase domains, respectively. Expression of dMiroT25N in the absence of endogenous dMiro caused premature lethality and arrested development at a pupal stage. dMiroT25N accumulated mitochondria in the soma of larval motor and sensory neurons, and prevented their kinesin-dependent and dynein-dependent distribution into axons and dendrites, respectively. dMiroT25N mutant mitochondria also were severely fragmented and exhibited reduced kinesin and dynein motility in axons. In contrast, dMiroT460N did not impair viability, mitochondrial size, or the distribution of mitochondria. However, dMiroT460N reduced dynein motility during retrograde mitochondrial transport in axons. Finally, we show that substitutions analogous to the constitutively active Ras-G12V mutation in dMiro's N-terminal and C-terminal GTPase domains cause neomorphic phenotypic effects that are likely unrelated to the normal function of each GTPase domain. Overall, our analysis indicates that dMiro's N-terminal GTPase domain is critically required for viability, mitochondrial size, and the distribution of mitochondria out of the neuronal soma regardless of the employed motor, likely by promoting the transition from a stationary to a motile state.
authors: Department of Neuroscience, Graduate Interdisciplinary Program in Neuroscience, and.
authors: Milos
authors: M
authors: Babic
authors: Department of Neuroscience, Graduate Program in Biochemistry and Molecular & Cellular Biology.
authors: Gary J
authors: GJ
authors: Russo
authors: Department of Neuroscience.
authors: Andrea J
authors: AJ
authors: Wellington
authors: Department of Neuroscience, Undergraduate Program in Neuroscience and Cognitive Science, University of Arizona, Tucson, Arizona 85721.
authors: Ryan M
authors: RM
authors: Sangston
authors: Department of Molecular and Cellular Biology.
authors: Migdalia
authors: M
authors: Gonzalez
authors: Department of Neuroscience, Department of Molecular and Cellular Biology, kez4@email.arizona.edu.
authors: Konrad E
authors: KE
authors: Zinsmaier
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D030801:Animals, Genetically Modified; D001370:Axonal Transport / Q000235:genetics*; D003712:Dendrites / Q000378:metabolism*; D004330:Drosophila; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004398:Dyneins / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism; D016547:Kinesins / Q000378:metabolism; D007814:Larva; D008928:Mitochondria / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure*; D017354:Point Mutation / Q000235:genetics; D012235:Rhodamines / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; D012235:Rhodamines; C401833:tetramethylrhodamine methyl ester; D049452:Green Fluorescent Proteins; D006735:Horseradish Peroxidase; D020558:GTP Phosphohydrolases; C504427:Miro protein, Drosophila; D004398:Dyneins; D016547:Kinesins; D020741:rho GTP-Binding Proteins
keywords: Miro; mitochondria; transport