title: Axonal localization and mitochondrial association of precursor microRNA 338.
abstract: MicroRNAs (miRNAs) selectively localize to subcompartments of the neuron, such as dendrites, axons, and presynaptic terminals, where they regulate the local protein synthesis of their putative target genes. In addition to mature miRNAs, precursor miRNAs (pre-miRNAs) have also been shown to localize to somatodendritic and axonal compartments. miRNA-338 (miR-338) regulates the local expression of several nuclear-encoded mitochondrial mRNAs within axons of sympathetic neurons. Previous work has shown that precursor miR-338 (pre-miR-338) introduced into the axon can locally be processed into mature miR-338, where it can regulate local ATP synthesis. However, the mechanisms underlying the localization of pre-miRNAs to the axonal compartment remain unknown. In this study, we investigated the axonal localization of pre-miR-338. Using proteomic and biochemical approaches, we provide evidence for the localization of pre-miR-338 to distal neuronal compartments and identify several constituents of the pre-miR-338 ribonucleoprotein complex. Furthermore, we found that pre-miR-338 is associated with the mitochondria in axons of superior cervical ganglion (SCG) neurons. The maintenance of mitochondrial function within axons requires the precise spatiotemporal synthesis of nuclear-encoded mRNAs, some of which are regulated by miR-338. Therefore, the association of pre-miR-338 with axonal mitochondria could serve as a reservoir of mature, biologically active miRNAs, which could coordinate the intra-axonal expression of multiple nuclear-encoded mitochondrial mRNAs.
authors.affiliation: Section on Neurobiology, Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892-4411, USA.
authors.forename: Jose Norberto S
authors.initials: JN
authors.lastname: Vargas
authors.affiliation: Section on Neurobiology, Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892-4411, USA.
authors.forename: Amar N
authors.initials: AN
authors.lastname: Kar
authors.affiliation: NINDS/NIMH Clinical Proteomics Unit, Division of Intramural Research Programs, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Kowalak
authors.affiliation: Section on Neurobiology, Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892-4411, USA.
authors.forename: Jenna R
authors.initials: JR
authors.lastname: Gale
authors.affiliation: Section on Neurobiology, Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892-4411, USA.
authors.forename: Armaz
authors.initials: A
authors.lastname: Aschrafi
authors.affiliation: Section on Neurobiology, Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892-4411, USA.
authors.forename: Cai-Yun
authors.initials: CY
authors.lastname: Chen
authors.affiliation: Section on Neurobiology, Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892-4411, USA.
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Gioio
authors.affiliation: Section on Neurobiology, Laboratory of Molecular Biology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, 20892-4411, USA. kaplanb@mail.nih.gov.
authors.forename: Barry B
authors.initials: BB
authors.lastname: Kaplan
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D053263:Gene Regulatory Networks; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D011485:Protein Binding; D012322:RNA Precursors / Q000378:metabolism*; D034443:RNA Transport; D017207:Rats, Sprague-Dawley; D043244:Ribonuclease III / Q000378:metabolism; D017783:Superior Cervical Ganglion / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; C573089:MIRN338 microRNA, rat; D035683:MicroRNAs; D012322:RNA Precursors; D043244:Ribonuclease III
keywords: Local translation; Mitochondrial translation; Post-transcriptional regulation; Proteomics; RNP granule; Subcellular localization; Superior cervical ganglion; Sympathetic neuron