title: Fine Astrocyte Processes Contain Very Small Mitochondria: Glial Oxidative Capability May Fuel Transmitter Metabolism.
abstract: The peripheral astrocyte process (PAP) is the glial compartment largely handling inactivation of transmitter glutamate, and supplying glutamate to the axon terminal. It is not clear how these energy demanding processes are fueled, and whether the PAP exhibits oxidative capability. Whereas the GFAP-positive perinuclear cytoplasm and stem process are rich in mitochondria, the PAP is often considered too narrow to contain mitochondria and might thus not rely on oxidative metabolism. Applying high resolution light microscopy, we investigate here the presence of mitochondria in the PAPs of freshly dissociated, isolated astrocytes. We provide an overview of the subcellular distribution and the approximate size of astrocytic mitochondria. A substantial proportion of the astrocyte's mitochondria are contained in the PAPs and, on the average, they are smaller there than in the stem processes. The majority of mitochondria in the stem and peripheral processes are surprisingly small (0.2-0.4 µm), spherical and not elongate, or tubular, which is supported by electron microscopy. The density of mitochondria is two to several times lower in the PAPs than in the stem processes. Thus, PAPs do not constitute a mitochondria free glial compartment but contain mitochondria in large numbers. No juxtaposition of mitochondria-containing PAPs and glutamatergic synapses has been reported. However, the issue of sufficient ATP concentrations in perisynaptic PAPs can be seen in the light of (1) the rapid, activity dependent PAP motility, and (2) the recently reported activity-dependent mitochondrial transport and immobilization leading to spatial, subcellular organisation of glutamate uptake and oxidative metabolism.
authors.affiliation: Dr. Senckenbergische Anatomie, Institut für Anatomie II, Goethe-Universität, Frankfurt am Main, Germany. Derouiche@em.uni-frankfurt.de.|Dr. Senckenbergisches Chronomedizinisches Institut, Goethe-Universität Frankfurt, Frankfurt am Main, Germany. Derouiche@em.uni-frankfurt.de.|Institute of Cellular Neurosciences, University of Bonn, Bonn, Germany. Derouiche@em.uni-frankfurt.de.
authors.forename: Amin
authors.initials: A
authors.lastname: Derouiche
authors.affiliation: Institute of Cellular Neurosciences, University of Bonn, Bonn, Germany.|Department of Neuroscience, Max Delbrück Center for Molecular Medicine, Berlin-Buch, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Haseleu
authors.affiliation: Dr. Senckenbergische Anatomie, Institut für Anatomie II, Goethe-Universität, Frankfurt am Main, Germany.|Dr. Senckenbergisches Chronomedizinisches Institut, Goethe-Universität Frankfurt, Frankfurt am Main, Germany.
authors.forename: Horst-Werner
authors.initials: HW
authors.lastname: Korf
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000648:ultrastructure; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D053142:Mitochondrial Size / Q000502:physiology*; D058953:Neural Stem Cells / Q000378:metabolism; D009457:Neuroglia / Q000378:metabolism* / Q000648:ultrastructure; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010084:Oxidation-Reduction; D017933:Peripheral Nervous System / Q000166:cytology / Q000378:metabolism; D061251:Primary Cell Culture; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism; D013569:Synapses / Q000378:metabolism
chemical_list: D005904:Glial Fibrillary Acidic Protein; D018377:Neurotransmitter Agents; D000255:Adenosine Triphosphate
keywords: Ezrin; Glia-synaptic interaction; Metabolic compartmentation; PAPs; Ultrastructure