scholarly journals MFF-dependent mitochondrial fission regulates presynaptic release and axon branching by limiting axonal mitochondria size

2018 ◽  
Author(s):  
Tommy L. Lewis ◽  
Seok-Kyu Kwon ◽  
Annie Lee ◽  
Reuben Shaw ◽  
Franck Polleux
Keyword(s):  
Pyramidal Neurons ◽  
Mitochondrial Fission ◽  
Axon Branching ◽  
Atp Production ◽  
Terminal Axon ◽  
Cortical Pyramidal Neurons ◽  
Presynaptic Release ◽  
Organelle Morphology

ABSTRACTNeurons display extreme degrees of polarization, including compartment-specific organelle morphology. In cortical pyramidal neurons, dendritic mitochondria are long and tubular whereas axonal mitochondria display uniformly short length. Here, we explored the functional significance of maintaining small mitochondria for axonal development in vitro and in vivo. We report that the Drp1 ‘receptor’ Mitochondrial fission factor (MFF) is required for determining the size of mitochondria entering the axon and then for maintenance of their size along the distal portions of the axon without affecting their trafficking properties, presynaptic capture, membrane potential or capacity for ATP production. Strikingly, this increase in presynaptic mitochondrial size upon MFF downregulation augments their capacity for Ca2+ ([Ca2+]m) uptake during neurotransmission, leading to reduced presynaptic [Ca2+]c accumulation, decreased presynaptic release and terminal axon branching. Our results uncover a novel mechanism controlling neurotransmitter release and axon branching through fission-dependent regulation of presynaptic mitochondrial size.

scholarly journals Defective Dendrite Elongation but Normal Fertility in Mice Lacking the Rho-Like GTPase Activator Dbl

2002 ◽  
Vol 22 (9) ◽  
pp. 3140-3148 ◽  
Author(s):  
Emilio Hirsch ◽  
Michela Pozzato ◽  
Alessandro Vercelli ◽  
Laura Barberis ◽  
Ornella Azzolino ◽  
...  
Keyword(s):  
Pyramidal Neurons ◽  
Embryonic Stem ◽  
Large Family ◽  
Small Gtpases ◽  
Normal Morphology ◽  
Targeted Deletion ◽  
Cortical Pyramidal Neurons ◽  
Rho Family

ABSTRACT Dbl is the prototype of a large family of GDP-GTP exchange factors for small GTPases of the Rho family. In vitro, Dbl is known to activate Rho and Cdc42 and to induce a transformed phenotype. Dbl is specifically expressed in brain and gonads, but its in vivo functions are largely unknown. To assess its role in neurogenesis and gametogenesis, targeted deletion of the murine Dbl gene was accomplished in embryonic stem cells. Dbl-null mice are viable and did not show either decreased reproductive performances or obvious neurological defects. Histological analysis of mutant testis showed normal morphology and unaltered proliferation and survival of spermatogonia. Dbl-null brains indicated a correct disposition of the major neural structures. Analysis of cortical stratification indicated that Dbl is not crucial for neuronal migration. However, in distinct populations of Dbl-null cortical pyramidal neurons, the length of dendrites was significantly reduced, suggesting a role for Dbl in dendrite elongation.

scholarly journals Repeated hypoglycemia blunts the responsiveness of glucose-inhibited GHRH neurons by remodeling neural inputs and disrupting mitochondrial structure and function

2019 ◽  
Author(s):  
M Bayne ◽  
A Alvarsson ◽  
K Devarakonda ◽  
R Li ◽  
M Jimenez-Gonzalez ◽  
...  
Keyword(s):  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Glucose Deprivation ◽  
Glucose Sensing ◽  
Diabetic Patients ◽  
Hypoglycemia Unawareness ◽  
Atp Production ◽  
Low Glucose

AbstractHypoglycemia is a frequent complication of diabetes, limiting therapy and increasing morbidity and mortality. With recurrent hypoglycemia, the counter-regulatory response (CRR) to decreased blood glucose is blunted, resulting in hypoglycemia unawareness. The mechanisms leading to these blunted effects remain incompletely understood. Here, we identify, with in situ hybridization, immunohistochemistry and the tissue clearing capability of iDisco, that GHRH neurons represent a unique population of arcuate nucleus neurons activated by glucose deprivation in vivo. Repeated glucose deprivation reduces GHRH neuron activation and remodels excitatory and inhibitory inputs to GHRH neurons. We show low glucose sensing is coupled to GHRH neuron depolarization, decreased ATP production and mitochondrial fusion. Repeated hypoglycemia attenuates these responses during low glucose. By maintaining mitochondrial length with the small molecule, mdivi-1, we preserved hypoglycemia sensitivity in vitro and in vivo. Our findings present possible mechanisms for the blunting of the CRR, broaden significantly our understanding of the structure of GHRH neurons and for the fist time, propose that mitochondrial dynamics play an important role in hypoglycemia unawareness. We conclude that interventions targeting mitochondrial fission in GHRH neurons may offer a new pathway to prevent hypoglycemia unawareness in diabetic patients.

Activation of Serotonin Receptors Modulates Synaptic Transmission in Rat Cerebral Cortex

1999 ◽  
Vol 82 (6) ◽  
pp. 2989-2999 ◽  
Author(s):  
Fu-Ming Zhou ◽  
John J. Hablitz
Keyword(s):  
Cerebral Cortex ◽  
Pyramidal Neurons ◽  
Short Pulse ◽  
Inhibitory Neurons ◽  
Cellular Mechanisms ◽  
Postsynaptic Currents ◽  
Cortical Pyramidal Neurons ◽  
Immunohistochemical Studies

The cerebral cortex receives an extensive serotonergic (5-hydroxytryptamine, 5-HT) input. Immunohistochemical studies suggest that inhibitory neurons are the main target of 5-HT innervation. In vivo extracellular recordings have shown that 5-HT generally inhibited cortical pyramidal neurons, whereas in vitro studies have shown an excitatory action. To determine the cellular mechanisms underlying the diverse actions of 5-HT in the cortex, we examined its effects on cortical inhibitory interneurons and pyramidal neurons. We found that 5-HT, through activation of 5-HT2A receptors, induced a massive enhancement of spontaneous inhibitory postsynaptic currents (sIPSCs) in pyramidal neurons, lasting for ∼6 min. In interneurons, this 5-HT-induced enhancement of sIPSCs was much weaker. Activation of 5-HT2Areceptors also increased spontaneous excitatory postsynaptic currents (sEPSCs) in pyramidal neurons. This response desensitized less and at a slower rate. In contrast, 5-HT slightly decreased evoked IPSCs (eIPSCs) and eEPSCs. In addition, 5-HT via 5-HT3 receptors evoked a large and rapidly desensitizing inward current in a subset of interneurons and induced a transient enhancement of sIPSCs. Our results suggest that 5-HT has widespread effects on both interneurons and pyramidal neurons and that a short pulse of 5-HT is likely to induce inhibition whereas the prolonged presence of 5-HT may result in excitation.

scholarly journals Implantable microcoils for intracortical magnetic stimulation

2016 ◽  
Vol 2 (12) ◽  
pp. e1600889 ◽  
Author(s):  
Seung Woo Lee ◽  
Florian Fallegger ◽  
Bernard D. F. Casse ◽  
Shelley I. Fried
Keyword(s):  
Cortical Neurons ◽  
Magnetic Stimulation ◽  
Pyramidal Neurons ◽  
Brain Slices ◽  
Behavioral Responses ◽  
Wide Range ◽  
Cortical Pyramidal Neurons ◽  
Over Time

Neural prostheses that stimulate the neocortex have the potential to treat a wide range of neurological disorders. However, the efficacy of electrode-based implants remains limited, with persistent challenges that include an inability to create precise patterns of neural activity as well as difficulties in maintaining response consistency over time. These problems arise from fundamental limitations of electrodes as well as their susceptibility to implantation and have proven difficult to overcome. Magnetic stimulation can address many of these limitations, but coils small enough to be implanted into the cortex were not thought strong enough to activate neurons. We describe a new microcoil design and demonstrate its effectiveness for both activating cortical neurons and driving behavioral responses. The stimulation of cortical pyramidal neurons in brain slices in vitro was reliable and could be confined to spatially narrow regions (<60 μm). The spatially asymmetric fields arising from the coil helped to avoid the simultaneous activation of passing axons. In vivo implantation was safe and resulted in consistent and predictable behavioral responses. The high permeability of magnetic fields to biological substances may yield another important advantage because it suggests that encapsulation and other adverse effects of implantation will not diminish coil performance over time, as happens to electrodes. These findings suggest that a coil-based implant might be a useful alternative to existing electrode-based devices. The enhanced selectivity of microcoil-based magnetic stimulation will be especially useful for visual prostheses as well as for many brain-computer interface applications that require precise activation of the cortex.

scholarly journals All-Trans Retinoic Acid Increases DRP1 Levels and Promotes Mitochondrial Fission

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1202
Author(s):  
Bojjibabu Chidipi ◽  
Syed Islamuddin Shah ◽  
Michelle Reiser ◽  
Manasa Kanithi ◽  
Amanda Garces ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Mitochondrial Fission ◽  
Normal Function ◽  
Mitochondrial Network ◽  
Protein Levels ◽  
Trans Retinoic Acid ◽  
All Trans Retinoic Acid ◽  
Area And Perimeter

In the heart, mitochondrial homeostasis is critical for sustaining normal function and optimal responses to metabolic and environmental stressors. Mitochondrial fusion and fission are thought to be necessary for maintaining a robust population of mitochondria, and disruptions in mitochondrial fission and/or fusion can lead to cellular dysfunction. The dynamin-related protein (DRP1) is an important mediator of mitochondrial fission. In this study, we investigated the direct effects of the micronutrient retinoid all-trans retinoic acid (ATRA) on the mitochondrial structure in vivo and in vitro using Western blot, confocal, and transmission electron microscopy, as well as mitochondrial network quantification using stochastic modeling. Our results showed that ATRA increases DRP1 protein levels, increases the localization of DRP1 to mitochondria in isolated mitochondrial preparations. Our results also suggested that ATRA remodels the mitochondrial ultrastructure where the mitochondrial area and perimeter were decreased and the circularity was increased. Microscopically, mitochondrial network remodeling is driven by an increased rate of fission over fusion events in ATRA, as suggested by our numerical modeling. In conclusion, ATRA results in a pharmacologically mediated increase in the DRP1 protein. It also results in the modulation of cardiac mitochondria by promoting fission events, altering the mitochondrial network, and modifying the ultrastructure of mitochondria in the heart.

scholarly journals Non-alcoholic fatty liver disease in mice with hepatocyte-specific deletion of mitochondrial fission factor

Diabetologia ◽  
2021 ◽  
Author(s):  
Yukina Takeichi ◽  
Takashi Miyazawa ◽  
Shohei Sakamoto ◽  
Yuki Hanada ◽  
Lixiang Wang ◽  
...  
Keyword(s):  
Er Stress ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Primary Hepatocytes ◽  
Alcoholic Fatty Liver ◽  
Expression Of Genes ◽  
Specific Deletion

Abstract Aims/hypothesis Mitochondria are highly dynamic organelles continuously undergoing fission and fusion, referred to as mitochondrial dynamics, to adapt to nutritional demands. Evidence suggests that impaired mitochondrial dynamics leads to metabolic abnormalities such as non-alcoholic steatohepatitis (NASH) phenotypes. However, how mitochondrial dynamics are involved in the development of NASH is poorly understood. This study aimed to elucidate the role of mitochondrial fission factor (MFF) in the development of NASH. Methods We created mice with hepatocyte-specific deletion of MFF (MffLiKO). MffLiKO mice fed normal chow diet (NCD) or high-fat diet (HFD) were evaluated for metabolic variables and their livers were examined by histological analysis. To elucidate the mechanism of development of NASH, we examined the expression of genes related to endoplasmic reticulum (ER) stress and lipid metabolism, and the secretion of triacylglycerol (TG) using the liver and primary hepatocytes isolated from MffLiKO and control mice. Results MffLiKO mice showed aberrant mitochondrial morphologies with no obvious NASH phenotypes during NCD, while they developed full-blown NASH phenotypes in response to HFD. Expression of genes related to ER stress was markedly upregulated in the liver from MffLiKO mice. In addition, expression of genes related to hepatic TG secretion was downregulated, with reduced hepatic TG secretion in MffLiKO mice in vivo and in primary cultures of MFF-deficient hepatocytes in vitro. Furthermore, thapsigargin-induced ER stress suppressed TG secretion in primary hepatocytes isolated from control mice. Conclusions/interpretation We demonstrated that ablation of MFF in liver provoked ER stress and reduced hepatic TG secretion in vivo and in vitro. Moreover, MffLiKO mice were more susceptible to HFD-induced NASH phenotype than control mice, partly because of ER stress-induced apoptosis of hepatocytes and suppression of TG secretion from hepatocytes. This study provides evidence for the role of mitochondrial fission in the development of NASH. Graphical abstract

scholarly journals The Role of Herbal Bioactive Components in Mitochondria Function and Cancer Therapy

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Fangfang Tao ◽  
Yanrong Zhang ◽  
Zhiqian Zhang
Keyword(s):  
Cancer Therapy ◽  
Cancer Cell ◽  
Apoptotic Cell ◽  
Redox Status ◽  
Cancer Therapies ◽  
Bioactive Components ◽  
Atp Production

Mitochondria are highly dynamic double-membrane organelles which play a well-recognized role in ATP production, calcium homeostasis, oxidation-reduction (redox) status, apoptotic cell death, and inflammation. Dysfunction of mitochondria has long been observed in a number of human diseases, including cancer. Targeting mitochondria metabolism in tumors as a cancer therapeutic strategy has attracted much attention for researchers in recent years due to the essential role of mitochondria in cancer cell growth, apoptosis, and progression. On the other hand, a series of studies have indicated that traditional medicinal herbs, including traditional Chinese medicines (TCM), exert their potential anticancer effects as an effective adjunct treatment for alleviating the systemic side effects of conventional cancer therapies, for reducing the risk of recurrence and cancer mortality and for improving the quality of patients’ life. An amazing feature of these structurally diverse bioactive components is that majority of them target mitochondria to provoke cancer cell-specific death program. The aim of this review is to summarize the in vitro and in vivo studies about the role of these herbs, especially their bioactive compounds in the modulation of the disturbed mitochondrial function for cancer therapy.

scholarly journals NIK promotes metabolic adaptation of glioblastoma cells to bioenergetic stress

2021 ◽  
Vol 12 (3) ◽  
Author(s):  
Michael L. Kamradt ◽  
Ji-Ung Jung ◽  
Kathryn M. Pflug ◽  
Dong W. Lee ◽  
Victor Fanniel ◽  
...  
Keyword(s):  
Stress Responses ◽  
Glucose Deprivation ◽  
Metabolic Adaptation ◽  
Mitochondrial Morphology ◽  
Atp Production ◽  
Tumor Microenvironments ◽  
Iκb Kinase ◽  
Critical Measure

AbstractCancers, including glioblastoma multiforme (GBM), undergo coordinated reprogramming of metabolic pathways that control glycolysis and oxidative phosphorylation (OXPHOS) to promote tumor growth in diverse tumor microenvironments. Adaptation to limited nutrient availability in the microenvironment is associated with remodeling of mitochondrial morphology and bioenergetic capacity. We recently demonstrated that NF-κB-inducing kinase (NIK) regulates mitochondrial morphology to promote GBM cell invasion. Here, we show that NIK is recruited to the outer membrane of dividing mitochondria with the master fission regulator, Dynamin-related protein1 (DRP1). Moreover, glucose deprivation-mediated metabolic shift to OXPHOS increases fission and mitochondrial localization of both NIK and DRP1. NIK deficiency results in decreased mitochondrial respiration, ATP production, and spare respiratory capacity (SRC), a critical measure of mitochondrial fitness. Although IκB kinase α and β (IKKα/β) and NIK are required for OXPHOS in high glucose media, only NIK is required to increase SRC under glucose deprivation. Consistent with an IKK-independent role for NIK in regulating metabolism, we show that NIK phosphorylates DRP1-S616 in vitro and in vivo. Notably, a constitutively active DRP1-S616E mutant rescues oxidative metabolism, invasiveness, and tumorigenic potential in NIK−/− cells without inducing IKK. Thus, we establish that NIK is critical for bioenergetic stress responses to promote GBM cell pathogenesis independently of IKK. Our data suggest that targeting NIK may be used to exploit metabolic vulnerabilities and improve therapeutic strategies for GBM.

Effect of Common Anesthetics on Dendritic Properties in Layer 5 Neocortical Pyramidal Neurons

2008 ◽  
Vol 99 (3) ◽  
pp. 1394-1407 ◽  
Author(s):  
Sarah Potez ◽  
Matthew E. Larkum
Keyword(s):  
High Frequency ◽  
Pyramidal Neurons ◽  
Animal Experiments ◽  
Apical Dendrite ◽  
Network Activity ◽  
Calcium Spikes ◽  
Firing Properties ◽  
The Impact

Understanding the impact of active dendritic properties on network activity in vivo has so far been restricted to studies in anesthetized animals. However, to date no study has been made to determine the direct effect of the anesthetics themselves on dendritic properties. Here, we investigated the effects of three types of anesthetics commonly used for animal experiments (urethane, pentobarbital and ketamine/xylazine). We investigated the generation of calcium spikes, the propagation of action potentials (APs) along the apical dendrite and the somatic firing properties in the presence of anesthetics in vitro using dual somatodendritic whole cell recordings. Calcium spikes were evoked with dendritic current injection and high-frequency trains of APs at the soma. Surprisingly, we found that the direct actions of anesthetics on calcium spikes were very different. Two anesthetics (urethane and pentobarbital) suppressed dendritic calcium spikes in vitro, whereas a mixture of ketamine and xylazine enhanced them. Propagation of spikes along the dendrite was not significantly affected by any of the anesthetics but there were various changes in somatic firing properties that were highly dependent on the anesthetic. Last, we examined the effects of anesthetics on calcium spike initiation and duration in vivo using high-frequency trains of APs generated at the cell body. We found the same anesthetic-dependent direct effects in addition to an overall reduction in dendritic excitability in anesthetized rats with all three anesthetics compared with the slice preparation.

Sign in / Sign up

Export Citation Format

Share Document