Loss of Local Astrocyte Support Disrupts Action Potential Propagation and Glutamate Release Synchrony from Unmyelinated Hippocampal Axon Terminals In Vitro

Sobieski, Courtney; Jiang, Xiaoping; Crawford, Devon C.; Mennerick, Steven

doi:10.1523/jneurosci.1289-15.2015

Cited by 19 publications

(21 citation statements)

References 66 publications

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“…First, we found that inhibition of oxidative phosphorylation alone, rather than glycolysis alone, produced changes to sodium current and action potential waveform. Second, because hippocampal glutamate release is quite sensitive to changes in action potential waveform (Prakriya and Mennerick, 2000;Meeks and Mennerick, 2004;Sobieski et al, 2015;Lujan et al, 2016), if the somatic action potential waveform changes that we observed after oligo treatment alone were propagated to terminals, then we would have expected strong alteration of transmitter release. Instead, we found that the changes to excitability produced by oligo alone were not associated with deficits in evoked PSCs.…”

Section: Discussionmentioning

confidence: 91%

“…7A), but many other facets of evoked transmission are intact (Sobieski et al, 2015). Recovery of EPSCs after the vesicle depletion challenge was slightly depressed in Ϫastrocyte neurons compared with ϩastrocyte neurons when recorded in control medium (Fig.…”

Section: Endogenous Monocarboxylate Powers Oxidative Phosphorylation mentioning

confidence: 88%

“…Neurons were plated at a low density (ϳ100 cells/mm Ϫ2 ). Positive and negative astrocyte microcultures were prepared as described previously (Sobieski et al, 2015). Briefly, 25 mm glass coverslips were stamped with a polydimethylsiloxane microstamp coated with 0.5 mg/ml collagen to create 150-to 200-m-diameter microdots and backfilled with a nonpermissive substrate poly-L-lysine grafted polyethylene glycol [PLL(20 kDa)-g(3.5)-PEG(2 kDa); Surface Solutions] at a concentration of 10 g/ml in PBS for 1 h and then washed with 1ϫ PBS.…”

Section: Methodsmentioning

confidence: 99%

“…Extracellular recording solutions do not contain exogenous monocarboxylates, so, based on prevailing views, lactate would be shuttled on demand from astrocytes to neurons during increased glutamate signaling (e.g., after vesicle depletion) to supply the TCA cycle with pyruvate (Pellerin andMagistretti, 1994, 2012). Microcultures provide a unique opportunity to test local shuttling and we tested the local shuttle hypothesis by culturing neurons in the absence of contact with an astrocyte bed (Sobieski et al, 2015). We showed previously that neurons without astrocyte contact exhibit altered synchrony of evoked glutamate release (Ϫastro-cyte; Fig.…”

Section: Endogenous Monocarboxylate Powers Oxidative Phosphorylation mentioning

confidence: 99%

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Differential Presynaptic ATP Supply for Basal and High-Demand Transmission

Sobieski¹,

Fitzpatrick

Mennerick

2017

J. Neurosci.

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The relative contributions of glycolysis and oxidative phosphorylation to neuronal presynaptic energy demands are unclear. In rat hippocampal neurons, ATP production by either glycolysis or oxidative phosphorylation alone sustained basal evoked synaptic transmission for up to 20 min. However, combined inhibition of both ATP sources abolished evoked transmission. Neither action potential propagation failure nor depressed Ca 2ϩ influx explained loss of evoked synaptic transmission. Rather, inhibition of ATP synthesis caused massive spontaneous vesicle exocytosis, followed by arrested endocytosis, accounting for the disappearance of evoked postsynaptic currents. In contrast to its weak effects on basal transmission, inhibition of oxidative phosphorylation alone depressed recovery from vesicle depletion. Local astrocytic lactate shuttling was not required. Instead, either ambient monocarboxylates or neuronal glycolysis was sufficient to supply requisite substrate. In summary, basal transmission can be sustained by glycolysis, but strong presynaptic demands are met preferentially by oxidative phosphorylation, which can be maintained by bulk but not local monocarboxylates or by neuronal glycolysis.

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Section: Discussionmentioning

confidence: 91%

Section: Endogenous Monocarboxylate Powers Oxidative Phosphorylation mentioning

confidence: 88%

Section: Methodsmentioning

confidence: 99%

Section: Endogenous Monocarboxylate Powers Oxidative Phosphorylation mentioning

confidence: 99%

See 2 more Smart Citations

Differential Presynaptic ATP Supply for Basal and High-Demand Transmission

Sobieski¹,

Fitzpatrick

Mennerick

2017

J. Neurosci.

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“…Hippocampal and cortical neurons were prepared from individual P0-P1 mouse pups using a modification of methods described for rat neuronal culture 21 . Mouse pups were genotyped after the fact to determine presence or absence of the MFN2*T105M transgene; neurons derived from mice lacking the transgene were designated as normal controls.…”

Section: Methodsmentioning

confidence: 99%

Correcting mitochondrial fusion by manipulating mitofusin conformations

Franco

Kitsis

Fleischer

et al. 2016

Nature

197

210

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Summary Mitochondria are dynamic organelles, remodeling and exchanging contents during cyclic fusion and fission. Genetic mutations of mitofusin (Mfn) 2 interrupt mitochondrial fusion and cause the untreatable neurodegenerative condition, Charcot Marie Tooth disease type 2A (CMT2A). It has not been possible to directly modulate mitochondrial fusion, in part because the structural basis of mitofusin function is incompletely understood. Here we show that mitofusins adopt either a fusion-constrained or fusion-permissive molecular conformation directed by specific intramolecular binding interactions, and demonstrate that mitofusin-dependent mitochondrial fusion can be regulated by targeting these conformational transitions. Based on this model we engineered a cell-permeant minipeptide to destabilize fusion-constrained mitofusin and promote the fusion-permissive conformation, reversing mitochondrial abnormalities in cultured fibroblasts and neurons harboring CMT2A gene defects. The relationship between mitofusin conformational plasticity and mitochondrial dynamism uncovers a central mechanism regulating mitochondrial fusion whose manipulation can correct mitochondrial pathology triggered by defective or imbalanced mitochondrial dynamics.

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Arsenic, Cadmium, and Lead Like Troglitazone Trigger PPARγ-Dependent Poly (ADP-Ribose) Polymerase Expression and Subsequent Apoptosis in Rat Brain Astrocytes

et al. 2017

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We previously demonstrated that arsenic, cadmium, and lead mixture at environmentally relevant doses induces astrocyte apoptosis in the developing brain. Here, we investigated the mechanism and contribution of each metal in inducing the apoptosis. We hypothesized participation of transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ), reported to affect astrocyte survival. We treated cultured rat astrocytes with single metals and their combinations and performed apoptosis assay and measured PPARγ expression levels. We found that cadmium demonstrated maximum increase in PPARγ as well as apoptosis, followed by arsenic and then lead. Interestingly, we observed that the metals mimicked PPARγ agonist, troglitazone, and enhanced PPARγ-transcriptional activity. Co-treatment with PPARγ-siRNA or PPARγ-antagonist, GW9662, suppressed the astrocyte apoptosis, suggesting a prominent participation of PPARγ in metal(s)-induced astrocyte loss. We explored PPARγ-transcriptional activity and identify its target gene in apoptosis, performed in silico screening. We spotted PPARγ-response elements (PPREs) within poly(ADP-ribose) polymerase (PARP) gene, and through gel-shift assay verified metal(s)-mediated increased PPARγ binding to PARP-PPREs. Chromatin-immunoprecipitation and luciferase-reporter assays followed by real-time PCR and Western blotting proved PPRE-mediated PARP expression, where cadmium contributed most and lead least, and the effects of metal mixture were comparable with troglitazone. Eventually, dose-dependent increased cleaved-PARP/PARP ratio confirmed astrocyte apoptosis. Additionally, we found that PPARγ and PARP expressions were c-Jun N-terminal kinases and cyclin-dependent kinase5-dependent. In vivo treatment of developing rats with the metals corroborated enhanced PPARγ-dependent PARP and astrocyte apoptosis, where yet again cadmium contributed most. Overall, our study enlightens a novel PPARγ-dependent mechanism of As-, Cd-, and Pb-induced astrocyte apoptosis.

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Loss of Local Astrocyte Support Disrupts Action Potential Propagation and Glutamate Release Synchrony from Unmyelinated Hippocampal Axon Terminals In Vitro

Cited by 19 publications

References 66 publications

Differential Presynaptic ATP Supply for Basal and High-Demand Transmission

Differential Presynaptic ATP Supply for Basal and High-Demand Transmission

Correcting mitochondrial fusion by manipulating mitofusin conformations

Arsenic, Cadmium, and Lead Like Troglitazone Trigger PPARγ-Dependent Poly (ADP-Ribose) Polymerase Expression and Subsequent Apoptosis in Rat Brain Astrocytes

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