title: Abnormal intracellular calcium signaling and SNARE-dependent exocytosis contributes to SOD1G93A astrocyte-mediated toxicity in amyotrophic lateral sclerosis.
abstract: Motor neurons are progressively and predominantly degenerated in ALS, which is not only induced by multiple intrinsic pathways but also significantly influenced by the neighboring glial cells. In particular, astrocytes derived from the SOD1 mutant mouse model of ALS or from human familial or sporadic ALS patient brain tissue directly induce motor neuron death in culture; however, the mechanisms of pathological astroglial secretion remain unclear. Here we investigated abnormal calcium homeostasis and altered exocytosis in SOD1G93A astrocytes. We found that purinergic stimulation induces excess calcium release from the ER stores in SOD1G93A astrocytes, which results from the abnormal ER calcium accumulation and is independent of clearance mechanisms. Furthermore, pharmacological studies suggested that store-operated calcium entry (SOCE), a calcium refilling mechanism responsive to ER calcium depletion, is enhanced in SOD1G93A astrocytes. We found that oxidant-induced increased S-glutathionylation and calcium-independent puncta formation of the ER calcium sensor STIM1 underlies the abnormal SOCE response in SOD1G93A astrocytes. Enhanced SOCE contributes to ER calcium overload in SOD1G93A astrocytes and excess calcium release from the ER during ATP stimulation. In addition, ER calcium release induces elevated ATP release from SOD1G93A astrocytes, which can be inhibited by the overexpression of dominant-negative SNARE. Selective inhibition of exocytosis in SOD1G93A astrocytes significantly prevents astrocyte-mediated toxicity to motor neurons and delays disease onset in SOD1G93A mice. Our results characterize a novel mechanism responsible for calcium dysregulation in SOD1G93A astrocytes and provide the first in vivo evidence that astrocyte exocytosis contributes to the pathogenesis of ALS.
authors: Brain and Mind Research Institute and Department of Neurology, Weill Medical College of Cornell University, New York, New York 10065, and Department of Neuroscience and Sackler School of Biomedical Sciences, Tufts University, Boston, Massachusetts 02111.
authors: Hibiki
authors: H
authors: Kawamata
authors: Seng Kah
authors: SK
authors: Ng
authors: Natalia
authors: N
authors: Diaz
authors: Suzanne
authors: S
authors: Burstein
authors: Lydie
authors: L
authors: Morel
authors: Alexandra
authors: A
authors: Osgood
authors: Brittany
authors: B
authors: Sider
authors: Haruki
authors: H
authors: Higashimori
authors: Philip G
authors: PG
authors: Haydon
authors: Giovanni
authors: G
authors: Manfredi
authors: Yongjie
authors: Y
authors: Yang
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D018920:Coculture Techniques / Q000379:methods; D005089:Exocytosis / Q000502:physiology*; D005260:Female; D008297:Male; D051379:Mice; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism; D050600:SNARE Proteins / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism* / Q000633:toxicity
chemical_list: D050600:SNARE Proteins; C109415:SOD1 G93A protein; D013482:Superoxide Dismutase