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Brustovetsky T, Khanna R, Brustovetsky N. CRMP2 Participates in Regulating Mitochondrial Morphology and Motility in Alzheimer's Disease. Cells 2023; 12:cells12091287. [PMID: 37174687 PMCID: PMC10177167 DOI: 10.3390/cells12091287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 04/05/2023] [Accepted: 04/27/2023] [Indexed: 05/15/2023] Open
Abstract
Mitochondrial bioenergetics and dynamics (alterations in morphology and motility of mitochondria) play critical roles in neuronal reactions to varying energy requirements in health and disease. In Alzheimer's disease (AD), mitochondria undergo excessive fission and become less motile. The mechanisms leading to these alterations are not completely clear. Here, we show that collapsin response mediator protein 2 (CRMP2) is hyperphosphorylated in AD and that is accompanied by a decreased interaction of CRMP2 with Drp1, Miro 2, and Mitofusin 2, which are proteins involved in regulating mitochondrial morphology and motility. CRMP2 was hyperphosphorylated in postmortem brain tissues of AD patients, in brain lysates, and in cultured cortical neurons from the double transgenic APP/PS1 mice, an AD mouse model. CRMP2 hyperphosphorylation and dissociation from its binding partners correlated with increased Drp1 recruitment to mitochondria, augmented mitochondrial fragmentation, and reduced mitochondrial motility. (S)-lacosamide ((S)-LCM), a small molecule that binds to CRMP2, decreased its phosphorylation at Ser 522 and Thr 509/514, and restored CRMP2's interaction with Miro 2, Drp1, and Mitofusin 2. This was paralleled by decreased Drp1 recruitment to mitochondria, diminished mitochondrial fragmentation, and improved motility of the organelles. Additionally, (S)-LCM-protected cultured cortical AD neurons from cell death. Thus, our data suggest that CRMP2, in a phosphorylation-dependent manner, participates in the regulation of mitochondrial morphology and motility, and modulates neuronal survival in AD.
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Affiliation(s)
- Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Medical Science Building, Room 362, Indianapolis, IN 46202, USA
| | - Rajesh Khanna
- Department of Molecular Pathobiology, New York University, New York, NY 10010, USA
- College of Dentistry, NYU Pain Research Center, New York University, New York, NY 10010, USA
- Department of Neuroscience and Physiology and Neuroscience Institute, School of Medicine, New York University, New York, NY 10010, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Medical Science Building, Room 362, Indianapolis, IN 46202, USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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2
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Bertholet A, Natale A, Bisignano P, Suzuki J, Fedorenko A, Hamilton J, Brustovetsky T, Kazak L, Chouchani ET, Brustovetsky N, Grabe M, Kirichok YV. Mitochondrial uncouplers induce proton leak by activating AAC and UCP1. Biophys J 2023; 122:306a. [PMID: 36783532 DOI: 10.1016/j.bpj.2022.11.1721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Ambre Bertholet
- University of California San Francisco, San Francisco, CA, USA
| | - Andrew Natale
- University of California San Francisco, San Francisco, CA, USA
| | - Paola Bisignano
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA, USA
| | - Junji Suzuki
- University of California San Francisco, San Francisco, CA, USA
| | - Andriy Fedorenko
- Department of Physiology, University of California San Francisco, San Francisco, CA, USA
| | - James Hamilton
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN, USA
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN, USA
| | | | | | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN, USA
| | - Michael Grabe
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA, USA
| | - Yuriy V Kirichok
- Department of Physiology, University of California San Francisco, San Francisco, CA, USA
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3
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Bertholet AM, Natale AM, Bisignano P, Suzuki J, Fedorenko A, Hamilton J, Brustovetsky T, Kazak L, Garrity R, Chouchani ET, Brustovetsky N, Grabe M, Kirichok Y. Mitochondrial uncouplers induce proton leak by activating AAC and UCP1. Nature 2022; 606:180-187. [PMID: 35614225 PMCID: PMC9646675 DOI: 10.1038/s41586-022-04747-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/08/2022] [Indexed: 11/08/2022]
Abstract
Mitochondria generate heat due to H+ leak (IH) across their inner membrane1. IH results from the action of long-chain fatty acids on uncoupling protein 1 (UCP1) in brown fat2-6 and ADP/ATP carrier (AAC) in other tissues1,7-9, but the underlying mechanism is poorly understood. As evidence of pharmacological activators of IH through UCP1 and AAC is lacking, IH is induced by protonophores such as 2,4-dinitrophenol (DNP) and cyanide-4-(trifluoromethoxy) phenylhydrazone (FCCP)10,11. Although protonophores show potential in combating obesity, diabetes and fatty liver in animal models12-14, their clinical potential for treating human disease is limited due to indiscriminately increasing H+ conductance across all biological membranes10,11 and adverse side effects15. Here we report the direct measurement of IH induced by DNP, FCCP and other common protonophores and find that it is dependent on AAC and UCP1. Using molecular structures of AAC, we perform a computational analysis to determine the binding sites for protonophores and long-chain fatty acids, and find that they overlap with the putative ADP/ATP-binding site. We also develop a mathematical model that proposes a mechanism of uncoupler-dependent IH through AAC. Thus, common protonophoric uncouplers are synthetic activators of IH through AAC and UCP1, paving the way for the development of new and more specific activators of these two central mediators of mitochondrial bioenergetics.
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Affiliation(s)
- Ambre M Bertholet
- Department of Physiology, University of California San Francisco, San Francisco, CA, USA
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Andrew M Natale
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA, USA
| | - Paola Bisignano
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA, USA
| | - Junji Suzuki
- Department of Physiology, University of California San Francisco, San Francisco, CA, USA
| | - Andriy Fedorenko
- Department of Physiology, University of California San Francisco, San Francisco, CA, USA
| | - James Hamilton
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN, USA
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN, USA
| | - Lawrence Kazak
- Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Ryan Garrity
- Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Edward T Chouchani
- Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, IN, USA
| | - Michael Grabe
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, CA, USA.
| | - Yuriy Kirichok
- Department of Physiology, University of California San Francisco, San Francisco, CA, USA.
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Brustovetsky T, Khanna R, Brustovetsky N. Involvement of CRMP2 in Regulation of Mitochondrial Morphology and Motility in Huntington's Disease. Cells 2021; 10:cells10113172. [PMID: 34831395 PMCID: PMC8619197 DOI: 10.3390/cells10113172] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 10/28/2021] [Accepted: 11/09/2021] [Indexed: 01/29/2023] Open
Abstract
Mitochondrial morphology and motility (mitochondrial dynamics) play a major role in the proper functioning of distant synapses. In Huntington’s disease (HD), mitochondria become fragmented and less motile, but the mechanisms leading to these changes are not clear. Here, we found that collapsin response mediator protein 2 (CRMP2) interacted with Drp1 and Miro 2, proteins involved in regulating mitochondrial dynamics. CRMP2 interaction with these proteins inversely correlated with CRMP2 phosphorylation. CRMP2 was hyperphosphorylated in postmortem brain tissues of HD patients, in human neurons derived from induced pluripotent stem cells from HD patients, and in cultured striatal neurons from HD mouse model YAC128. At the same time, CRMP2 interaction with Drp1 and Miro 2 was diminished in HD neurons. The CRMP2 hyperphosphorylation and dissociation from Drp1 and Miro 2 correlated with increased fission and suppressed motility. (S)-lacosamide ((S)-LCM), a small molecule that binds to CRMP2, decreased its phosphorylation at Thr 509/514 and Ser 522 and rescued CRMP2’s interaction with Drp1 and Miro 2. This was accompanied by reduced mitochondrial fission and enhanced mitochondrial motility. Additionally, (S)-LCM exerted a neuroprotective effect in YAC128 cultured neurons. Thus, our data suggest that CRMP2 may regulate mitochondrial dynamics in a phosphorylation-dependent manner and modulate neuronal survival in HD.
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Affiliation(s)
- Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
| | - Rajesh Khanna
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ 85721, USA;
- Center for Innovation in Brain Sciences, University of Arizona, Tucson, AZ 85721, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Correspondence: ; Tel.: +1-317-278-9229; Fax: +1-317-274-7714
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Hamilton J, Brustovetsky T, Brustovetsky N. The effect of mitochondrial calcium uniporter and cyclophilin D knockout on resistance of brain mitochondria to Ca 2+-induced damage. J Biol Chem 2021; 296:100669. [PMID: 33864812 PMCID: PMC8131324 DOI: 10.1016/j.jbc.2021.100669] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 04/10/2021] [Accepted: 04/13/2021] [Indexed: 12/14/2022] Open
Abstract
The mitochondrial calcium uniporter (MCU) and cyclophilin D (CyD) are key players in induction of the permeability transition pore (PTP), which leads to mitochondrial depolarization and swelling, the major signs of Ca2+-induced mitochondrial damage. Mitochondrial depolarization inhibits ATP production, whereas swelling results in the release of mitochondrial pro-apoptotic proteins. The extent to which simultaneous deletion of MCU and CyD inhibits PTP induction and prevents damage of brain mitochondria is not clear. Here, we investigated the effects of MCU and CyD deletion on the propensity for PTP induction using mitochondria isolated from the brains of MCU-KO, CyD-KO, and newly created MCU/CyD-double knockout (DKO) mice. Neither deletion of MCU nor of CyD affected respiration or membrane potential in mitochondria isolated from the brains of these mice. Mitochondria from MCU-KO and MCU/CyD-DKO mice displayed reduced Ca2+ uptake and diminished extent of PTP induction. The Ca2+ uptake by mitochondria from CyD-KO mice was increased compared with mitochondria from WT mice. Deletion of CyD prevented mitochondrial swelling and resulted in transient depolarization in response to Ca2+, but it did not prevent Ca2+-induced delayed mitochondrial depolarization. Mitochondria from MCU/CyD-DKO mice did not swell in response to Ca2+, but they did exhibit mild sustained depolarization. Dibucaine, an inhibitor of the Ca2+-activated mitochondrial phospholipase A2, attenuated and bovine serum albumin completely eliminated the sustained depolarization. This suggests the involvement of phospholipase A2 and free fatty acids. Thus, in addition to induction of the classical PTP, alternative deleterious mechanisms may contribute to mitochondrial damage following exposure to elevated Ca2+.
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Affiliation(s)
- James Hamilton
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana, USA.
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Hamilton J, Brustovetsky T, Khanna R, Brustovetsky N. Mutant huntingtin does not cross the mitochondrial outer membrane. Hum Mol Genet 2020; 29:2962-2975. [PMID: 32821928 PMCID: PMC7566381 DOI: 10.1093/hmg/ddaa185] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 07/21/2020] [Accepted: 08/15/2020] [Indexed: 12/29/2022] Open
Abstract
Mutant huntingtin (mHTT) is associated with mitochondria, but the exact mitochondrial location of mHTT has not been definitively established. Recently, it was reported that mHTT is present in the intermembrane space and inhibits mitochondrial protein import by interacting with TIM23, a major component of mitochondrial protein import machinery, but evidence for functional ramifications were not provided. We assessed mHTT location using synaptic and nonsynaptic mitochondria isolated from brains of YAC128 mice and subjected to alkali treatment or limited trypsin digestion. Mitochondria were purified either with discontinuous Percoll gradient or with anti-TOM22-conjugated iron microbeads. We also used mitochondria isolated from postmortem brain tissues of unaffected individuals and HD patients. Our results demonstrate that mHTT is located on the cytosolic side of the mitochondrial outer membrane (MOM) but does not cross it. This refutes the hypothesis that mHTT may interact with TIM23 and inhibit mitochondrial protein import. The levels of expression of nuclear-encoded, TIM23-transported mitochondrial proteins ACO2, TUFM, IDH3A, CLPP and mitochondrially encoded and synthesized protein mtCO1 were similar in mitochondria from YAC128 mice and their wild-type littermates as well as in mitochondria from postmortem brain tissues of unaffected individuals and HD patients, supporting the lack of deficit in mitochondrial protein import. Regardless of purification technique, mitochondria from YAC128 and WT mice had similar respiratory activities and mitochondrial membrane potentials. Thus, our data argue against mHTT crossing the MOM and entering into the mitochondrial intermembrane space, making it highly unlikely that mHTT interacts with TIM23 and inhibits protein import in intact mitochondria.
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Affiliation(s)
| | | | - Rajesh Khanna
- Department of Pharmacology, University of Arizona, Tucson, AZ 85721, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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7
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Hamilton J, Brustovetsky T, Brustovetsky N. Mutant huntingtin fails to directly impair brain mitochondria. J Neurochem 2019; 151:716-731. [PMID: 31418857 PMCID: PMC6917837 DOI: 10.1111/jnc.14852] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/17/2019] [Accepted: 08/06/2019] [Indexed: 12/15/2022]
Abstract
Although the mechanisms by which mutant huntingtin (mHtt) results in Huntington's disease (HD) remain unclear, mHtt-induced mitochondrial defects were implicated in HD pathogenesis. The effect of mHtt could be mediated by transcriptional alterations, by direct interaction with mitochondria, or by both. In the present study, we tested a hypothesis that mHtt directly damages mitochondria. To test this hypothesis, we applied brain cytosolic fraction from YAC128 mice, containing mHtt, to brain non-synaptic and synaptic mitochondria from wild-type mice and assessed mitochondrial respiration with a Clark-type oxygen electrode, membrane potential and Ca2+ uptake capacity with tetraphenylphosphonium (TPP+ )- and Ca2+ -sensitive electrodes, respectively, and, reactive oxygen species production with Amplex Red assay. The amount of mHtt bound to mitochondria following incubation with mHtt-containing cytosolic fraction was greater than the amount of mHtt bound to brain mitochondria isolated from YAC128 mice. Despite mHtt binding to wild-type mitochondria, no abnormalities in mitochondrial functions were detected. This is consistent with our previous results demonstrating the lack of defects in brain mitochondria isolated from R6/2 and YAC128 mice. This, however, could be because of partial loss of mitochondrially bound mHtt during the isolation procedure. Consequently, we increased the amount of mitochondrially bound mHtt by incubating brain non-synaptic and synaptic mitochondria isolated from YAC128 mice with mHtt-containing cytosolic fraction. Despite the enrichment of YAC128 brain mitochondria with mHtt, mitochondrial functions (respiration, membrane potential, reactive oxygen species production, Ca2+ uptake capacity) remained unchanged. Overall, our results suggest that mHtt does not directly impair mitochondrial functions, arguing against the involvement of this mechanism in HD pathogenesis. Open Science: This manuscript was awarded with the Open Materials Badge For more information see: https://cos.io/our-services/open-science-badges/.
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Affiliation(s)
- James Hamilton
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN
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François-Moutal L, Dustrude ET, Wang Y, Brustovetsky T, Dorame A, Ju W, Moutal A, Perez-Miller S, Brustovetsky N, Gokhale V, Khanna M, Khanna R. Inhibition of the Ubc9 E2 SUMO-conjugating enzyme-CRMP2 interaction decreases NaV1.7 currents and reverses experimental neuropathic pain. Pain 2018; 159:2115-2127. [PMID: 29847471 PMCID: PMC6150792 DOI: 10.1097/j.pain.0000000000001294] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We previously reported that destruction of the small ubiquitin-like modifier (SUMO) modification site in the axonal collapsin response mediator protein 2 (CRMP2) was sufficient to selectively decrease trafficking of the voltage-gated sodium channel NaV1.7 and reverse neuropathic pain. Here, we further interrogate the biophysical nature of the interaction between CRMP2 and the SUMOylation machinery, and test the hypothesis that a rationally designed CRMP2 SUMOylation motif (CSM) peptide can interrupt E2 SUMO-conjugating enzyme Ubc9-dependent modification of CRMP2 leading to a similar suppression of NaV1.7 currents. Microscale thermophoresis and amplified luminescent proximity homogeneous alpha assay revealed a low micromolar binding affinity between CRMP2 and Ubc9. A heptamer peptide harboring CRMP2's SUMO motif, also bound with similar affinity to Ubc9, disrupted the CRMP2-Ubc9 interaction in a concentration-dependent manner. Importantly, incubation of a tat-conjugated cell-penetrating peptide (t-CSM) decreased sodium currents, predominantly NaV1.7, in a model neuronal cell line. Dialysis of t-CSM peptide reduced CRMP2 SUMOylation and blocked surface trafficking of NaV1.7 in rat sensory neurons. Fluorescence dye-based imaging in rat sensory neurons demonstrated inhibition of sodium influx in the presence of t-CSM peptide; by contrast, calcium influx was unaffected. Finally, t-CSM effectively reversed persistent mechanical and thermal hypersensitivity induced by a spinal nerve injury, a model of neuropathic pain. Structural modeling has now identified a pocket-harboring CRMP2's SUMOylation motif that, when targeted through computational screening of ligands/molecules, is expected to identify small molecules that will biochemically and functionally target CRMP2's SUMOylation to reduce NaV1.7 currents and reverse neuropathic pain.
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Affiliation(s)
- Liberty François-Moutal
- Department of Pharmacology, The University of Arizona Health Sciences, Tucson, Arizona 85724
| | - Erik T. Dustrude
- Department of Pharmacology, The University of Arizona Health Sciences, Tucson, Arizona 85724
| | - Yue Wang
- Department of Pharmacology, The University of Arizona Health Sciences, Tucson, Arizona 85724
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, and Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Angie Dorame
- Department of Pharmacology, The University of Arizona Health Sciences, Tucson, Arizona 85724
| | - Weina Ju
- Department of Neurology, First Hospital of Jilin University, Jilin University, 71 Xinmin Street, Changchun, 130021, Jilin Province, China
- Department of Pharmacology, First Hospital of Jilin University, Jilin University, 71 Xinmin Street, Changchun, 130021, Jilin Province, China
| | - Aubin Moutal
- Department of Pharmacology, The University of Arizona Health Sciences, Tucson, Arizona 85724
| | - Samantha Perez-Miller
- Department of Pharmacology, The University of Arizona Health Sciences, Tucson, Arizona 85724
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, and Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Vijay Gokhale
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona Health Sciences, Tucson, Arizona 85724
| | - May Khanna
- Department of Pharmacology, The University of Arizona Health Sciences, Tucson, Arizona 85724
- The Center for Innovation in Brain Sciences, The University of Arizona Health Sciences, Tucson, Arizona 85724
| | - Rajesh Khanna
- Department of Pharmacology, The University of Arizona Health Sciences, Tucson, Arizona 85724
- Neuroscience Graduate Interdisciplinary Program, College of Medicine, The University of Arizona Health Sciences, Tucson, Arizona 85724
- The Center for Innovation in Brain Sciences, The University of Arizona Health Sciences, Tucson, Arizona 85724
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9
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Hamilton J, Brustovetsky T, Rysted JE, Lin Z, Usachev YM, Brustovetsky N. Deletion of mitochondrial calcium uniporter incompletely inhibits calcium uptake and induction of the permeability transition pore in brain mitochondria. J Biol Chem 2018; 293:15652-15663. [PMID: 30154242 DOI: 10.1074/jbc.ra118.002926] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 08/22/2018] [Indexed: 11/06/2022] Open
Abstract
Ca2+ influx into mitochondria is mediated by the mitochondrial calcium uniporter (MCU), whose identity was recently revealed as a 40-kDa protein that along with other proteins forms the mitochondrial Ca2+ uptake machinery. The MCU is a Ca2+-conducting channel spanning the inner mitochondrial membrane. Here, deletion of the MCU completely inhibited Ca2+ uptake in liver, heart, and skeletal muscle mitochondria. However, in brain nonsynaptic and synaptic mitochondria from neuronal somata/glial cells and nerve terminals, respectively, the MCU deletion slowed, but did not completely block, Ca2+ uptake. Under resting conditions, brain MCU-KO mitochondria remained polarized, and in brain MCU-KO mitochondria, the electrophoretic Ca2+ ionophore ETH129 significantly accelerated Ca2+ uptake. The residual Ca2+ uptake in brain MCU-KO mitochondria was insensitive to inhibitors of mitochondrial Na+/Ca2+ exchanger and ryanodine receptor (CGP37157 and dantrolene, respectively), but was blocked by the MCU inhibitor Ru360. Respiration of WT and MCU-KO brain mitochondria was similar except that for mitochondria that oxidized pyruvate and malate, Ca2+ more strongly inhibited respiration in WT than in MCU-KO mitochondria. Of note, the MCU deletion significantly attenuated but did not completely prevent induction of the permeability transition pore (PTP) in brain mitochondria. Expression level of cyclophilin D and ATP content in mitochondria, two factors that modulate PTP induction, were unaffected by MCU-KO, whereas ADP was lower in MCU-KO than in WT brain mitochondria. Our results suggest the presence of an MCU-independent Ca2+ uptake pathway in brain mitochondria that mediates residual Ca2+ influx and induction of PTP in a fraction of the mitochondrial population.
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Affiliation(s)
| | | | - Jacob E Rysted
- the Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
| | - Zhihong Lin
- the Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
| | - Yuriy M Usachev
- the Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
| | - Nickolay Brustovetsky
- From the Department of Pharmacology and Toxicology and .,the Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202 and
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10
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Hamilton J, Brustovetsky T, Brustovetsky N. Oxidative metabolism and Ca 2+ handling in striatal mitochondria from YAC128 mice, a model of Huntington's disease. Neurochem Int 2017; 109:24-33. [PMID: 28062223 PMCID: PMC5495615 DOI: 10.1016/j.neuint.2017.01.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 12/29/2016] [Accepted: 01/02/2017] [Indexed: 01/30/2023]
Abstract
The mechanisms implicated in the pathology of Huntington's disease (HD) remain not completely understood, although dysfunction of mitochondrial oxidative metabolism and Ca2+ handling have been suggested as contributing factors. However, in our previous studies with mitochondria isolated from the whole brains of HD mice, we found no evidence for defects in mitochondrial respiration and Ca2+ handling. In the present study, we used the YAC128 mouse model of HD to evaluate the effect of mHtt on respiratory activity and Ca2+ uptake capacity of mitochondria isolated from the striatum, the most vulnerable brain region in HD. Isolated, Percoll-gradient purified striatal mitochondria from YAC128 mice were free of cytosolic and ER contaminations, but retained attached mHtt. Both nonsynaptic and synaptic striatal mitochondria isolated from early symptomatic 2-month-old YAC128 mice had similar respiratory rates and Ca2+ uptake capacities compared with mitochondria from wild-type FVB/NJ mice. Consistent with the lack of difference in mitochondrial respiration, we found that the expression of several nuclear-encoded proteins in striatal mitochondria was similar between wild-type and YAC128 mice. Taken together, our data demonstrate that mHtt does not alter respiration and Ca2+ uptake capacity in striatal mitochondria isolated from YAC128 mice, suggesting that respiratory defect and Ca2+ uptake deficiency most likely do not contribute to striatal pathology associated with HD.
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Affiliation(s)
- James Hamilton
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States; Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States.
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11
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Patel RR, Barbosa C, Brustovetsky T, Brustovetsky N, Cummins TR. Aberrant epilepsy-associated mutant Nav1.6 sodium channel activity can be targeted with cannabidiol. Brain 2016; 139:2164-81. [PMID: 27267376 DOI: 10.1093/brain/aww129] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 04/15/2016] [Indexed: 11/12/2022] Open
Abstract
Mutations in brain isoforms of voltage-gated sodium channels have been identified in patients with distinct epileptic phenotypes. Clinically, these patients often do not respond well to classic anti-epileptics and many remain refractory to treatment. Exogenous as well as endogenous cannabinoids have been shown to target voltage-gated sodium channels and cannabidiol has recently received attention for its potential efficacy in the treatment of childhood epilepsies. In this study, we further investigated the ability of cannabinoids to modulate sodium currents from wild-type and epilepsy-associated mutant voltage-gated sodium channels. We first determined the biophysical consequences of epilepsy-associated missense mutations in both Nav1.1 (arginine 1648 to histidine and asparagine 1788 to lysine) and Nav1.6 (asparagine 1768 to aspartic acid and leucine 1331 to valine) by obtaining whole-cell patch clamp recordings in human embryonic kidney 293T cells with 200 μM Navβ4 peptide in the pipette solution to induce resurgent sodium currents. Resurgent sodium current is an atypical near threshold current predicted to increase neuronal excitability and has been implicated in multiple disorders of excitability. We found that both mutations in Nav1.6 dramatically increased resurgent currents while mutations in Nav1.1 did not. We then examined the effects of anandamide and cannabidiol on peak transient and resurgent currents from wild-type and mutant channels. Interestingly, we found that cannabidiol can preferentially target resurgent sodium currents over peak transient currents generated by wild-type Nav1.6 as well as the aberrant resurgent and persistent current generated by Nav1.6 mutant channels. To further validate our findings, we examined the effects of cannabidiol on endogenous sodium currents from striatal neurons, and similarly we found an inhibition of resurgent and persistent current by cannabidiol. Moreover, current clamp recordings show that cannabidiol reduces overall action potential firing of striatal neurons. These findings suggest that cannabidiol could be exerting its anticonvulsant effects, at least in part, through its actions on voltage-gated sodium channels, and resurgent current may be a promising therapeutic target for the treatment of epilepsy syndromes.
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Affiliation(s)
- Reesha R Patel
- 1 Program in Medical Neuroscience, Neuroscience Research Building, 320 West 15th St, Indianapolis, IN, 46202, USA 2 Paul and Carole Stark Neurosciences Research Institute, 320 West 15th St, Indianapolis, IN, 46202, USA
| | - Cindy Barbosa
- 3 Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Tatiana Brustovetsky
- 3 Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Nickolay Brustovetsky
- 1 Program in Medical Neuroscience, Neuroscience Research Building, 320 West 15th St, Indianapolis, IN, 46202, USA 2 Paul and Carole Stark Neurosciences Research Institute, 320 West 15th St, Indianapolis, IN, 46202, USA 3 Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
| | - Theodore R Cummins
- 1 Program in Medical Neuroscience, Neuroscience Research Building, 320 West 15th St, Indianapolis, IN, 46202, USA 2 Paul and Carole Stark Neurosciences Research Institute, 320 West 15th St, Indianapolis, IN, 46202, USA 3 Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN, 46202, USA
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12
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Hamilton J, Pellman JJ, Brustovetsky T, Harris RA, Brustovetsky N. Oxidative metabolism and Ca2+ handling in isolated brain mitochondria and striatal neurons from R6/2 mice, a model of Huntington's disease. Hum Mol Genet 2016; 25:2762-2775. [PMID: 27131346 DOI: 10.1093/hmg/ddw133] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 04/07/2016] [Accepted: 04/25/2016] [Indexed: 01/25/2023] Open
Abstract
Alterations in oxidative metabolism and defects in mitochondrial Ca2+ handling have been implicated in the pathology of Huntington's disease (HD), but existing data are contradictory. We investigated the effect of human mHtt fragments on oxidative metabolism and Ca2+ handling in isolated brain mitochondria and cultured striatal neurons from the R6/2 mouse model of HD. Non-synaptic and synaptic mitochondria isolated from the brains of R6/2 mice had similar respiratory rates and Ca2+ uptake capacity compared with mitochondria from wild-type (WT) mice. Respiratory activity of cultured striatal neurons measured with Seahorse XF24 flux analyzer revealed unaltered cellular respiration in neurons derived from R6/2 mice compared with neurons from WT animals. Consistent with the lack of respiratory dysfunction, ATP content of cultured striatal neurons from R6/2 and WT mice was similar. Mitochondrial Ca2+ accumulation was also evaluated in cultured striatal neurons from R6/2 and WT animals. Our data obtained with striatal neurons derived from R6/2 and WT mice show that both glutamate-induced increases in cytosolic Ca2+ and subsequent carbonilcyanide p-triflouromethoxyphenylhydrazone-induced increases in cytosolic Ca2+ were similar between WT and R6/2, suggesting that mitochondria in neurons derived from both types of animals accumulated comparable amounts of Ca2+ Overall, our data argue against respiratory deficiency and impaired Ca2+ handling induced by human mHtt fragments in both isolated brain mitochondria and cultured striatal neurons from transgenic R6/2 mice.
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Affiliation(s)
| | | | | | - Robert A Harris
- Department of Biochemistry and Molecular Biology.,Richard L. Roudebush VA Medical Center, Indianapolis, IN, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology .,Stark Neuroscience Research InstituteIndiana University School of Medicine, Indianapolis, IN, USA
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13
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Pellman JJ, Hamilton J, Brustovetsky T, Brustovetsky N. Ca(2+) handling in isolated brain mitochondria and cultured neurons derived from the YAC128 mouse model of Huntington's disease. J Neurochem 2015; 134:652-67. [PMID: 25963273 PMCID: PMC4516671 DOI: 10.1111/jnc.13165] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 05/04/2015] [Accepted: 05/05/2015] [Indexed: 01/10/2023]
Abstract
We investigated Ca(2+) handling in isolated brain synaptic and non-synaptic mitochondria and in cultured striatal neurons from the YAC128 mouse model of Huntington's disease. Both synaptic and non-synaptic mitochondria from 2- and 12-month-old YAC128 mice had larger Ca(2+) uptake capacity than mitochondria from YAC18 and wild-type FVB/NJ mice. Synaptic mitochondria from 12-month-old YAC128 mice had further augmented Ca(2+) capacity compared with mitochondria from 2-month-old YAC128 mice and age-matched YAC18 and FVB/NJ mice. This increase in Ca(2+) uptake capacity correlated with an increase in the amount of mutant huntingtin protein (mHtt) associated with mitochondria from 12-month-old YAC128 mice. We speculate that this may happen because of mHtt-mediated sequestration of free fatty acids thereby increasing resistance of mitochondria to Ca(2+)-induced damage. In experiments with striatal neurons from YAC128 and FVB/NJ mice, brief exposure to 25 or 100 μM glutamate produced transient elevations in cytosolic Ca(2+) followed by recovery to near resting levels. Following recovery of cytosolic Ca(2+), mitochondrial depolarization with FCCP produced comparable elevations in cytosolic Ca(2+), suggesting similar Ca(2+) release and, consequently, Ca(2+) loads in neuronal mitochondria from YAC128 and FVB/NJ mice. Together, our data argue against a detrimental effect of mHtt on Ca(2+) handling in brain mitochondria of YAC128 mice. We demonstrate that mutant huntingtin (mHtt) binds to brain synaptic and nonsynaptic mitochondria and the amount of mitochondria-bound mHtt correlates with increased mitochondrial Ca(2+) uptake capacity. We propose that this may happen due to mHtt-mediated sequestration of free fatty acids thereby increasing resistance of mitochondria to Ca(2+)-induced damage.
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Affiliation(s)
- Jessica J. Pellman
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - James Hamilton
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis IN 46202, USA
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14
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Hamilton J, Pellman JJ, Brustovetsky T, Harris RA, Brustovetsky N. Oxidative metabolism in YAC128 mouse model of Huntington's disease. Hum Mol Genet 2015; 24:4862-78. [PMID: 26041817 DOI: 10.1093/hmg/ddv209] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 06/01/2015] [Indexed: 12/15/2022] Open
Abstract
Alterations in oxidative metabolism are considered to be one of the major contributors to Huntington's disease (HD) pathogenesis. However, existing data about oxidative metabolism in HD are contradictory. Here, we investigated the effect of mutant huntingtin (mHtt) on oxidative metabolism in YAC128 mice. Both mHtt and wild-type huntingtin (Htt) were associated with mitochondria and the amount of bound Htt was four-times higher than the amount of bound mHtt. Percoll gradient-purified brain synaptic and non-synaptic mitochondria as well as unpurified brain, liver and heart mitochondria, isolated from 2- and 10-month-old YAC128 mice and age-matched WT littermates had similar respiratory rates. There was no difference in mitochondrial membrane potential or ADP and ATP levels. Expression of selected nuclear-encoded mitochondrial proteins in 2- and 10-month-old YAC128 and WT mice was similar. Cultured striatal and cortical neurons from YAC128 and WT mice had similar respiratory and glycolytic activities as measured with Seahorse XF24 analyzer in medium containing 10 mm glucose and 15 mm pyruvate. In the medium with 2.5 mm glucose, YAC128 striatal neurons had similar respiration, but slightly lower glycolytic activity. Striatal neurons had lower maximal respiration compared with cortical neurons. In vivo experiments with YAC128 and WT mice showed similar O2 consumption, CO2 release, physical activity, food consumption and fasted blood glucose. However, YAC128 mice were heavier and had more body fat compared with WT mice. Overall, our data argue against respiratory deficiency in YAC128 mice and, consequently, suggest that mitochondrial respiratory dysfunction is not essential for HD pathogenesis.
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Affiliation(s)
| | | | | | - Robert A Harris
- Department of Biochemistry and Molecular Biology and Richard L. Roudebush VA Medical Center, Indianapolis, IN, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Department of Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA and
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15
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Brustovetsky T, Pellman JJ, Yang XF, Khanna R, Brustovetsky N. Collapsin response mediator protein 2 (CRMP2) interacts with N-methyl-D-aspartate (NMDA) receptor and Na+/Ca2+ exchanger and regulates their functional activity. J Biol Chem 2014; 289:7470-82. [PMID: 24474686 DOI: 10.1074/jbc.m113.518472] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Collapsin response mediator protein 2 (CRMP2) is traditionally viewed as an axonal growth protein involved in axon/dendrite specification. Here, we describe novel functions of CRMP2. A 15-amino acid peptide from CRMP2, fused to the TAT cell-penetrating motif of the HIV-1 protein, TAT-CBD3, but not CBD3 without TAT, attenuated N-methyl-d-aspartate receptor (NMDAR) activity and protected neurons against glutamate-induced Ca(2+) dysregulation, suggesting the key contribution of CRMP2 in these processes. In addition, TAT-CBD3, but not CBD3 without TAT or TAT-scramble peptide, inhibited increases in cytosolic Ca(2+) mediated by the plasmalemmal Na(+)/Ca(2+) exchanger (NCX) operating in the reverse mode. Co-immunoprecipitation experiments revealed an interaction between CRMP2 and NMDAR as well as NCX3 but not NCX1. TAT-CBD3 disrupted CRMP2-NMDAR interaction without change in NMDAR localization. In contrast, TAT-CBD3 augmented the CRMP2-NCX3 co-immunoprecipitation, indicating increased interaction or stabilization of a complex between these proteins. Immunostaining with an anti-NCX3 antibody revealed that TAT-CBD3 induced NCX3 internalization, suggesting that both reverse and forward modes of NCX might be affected. Indeed, the forward mode of NCX, evaluated in experiments with ionomycin-induced Ca(2+) influx into neurons, was strongly suppressed by TAT-CBD3. Knockdown of CRMP2 with short interfering RNA (siRNA) prevented NCX3 internalization in response to TAT-CBD3 exposure. Moreover, CRMP2 down-regulation strongly attenuated TAT-CBD3-induced inhibition of reverse NCX. Overall, our results demonstrate that CRMP2 interacts with NCX and NMDAR and that TAT-CBD3 protects against glutamate-induced Ca(2+) dysregulation most likely via suppression of both NMDAR and NCX activities. Our results further clarify the mechanism of action of TAT-CBD3 and identify a novel regulatory checkpoint for NMDAR and NCX function based on CRMP2 interaction with these proteins.
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16
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Ashpole NM, Chawla AR, Martin MP, Brustovetsky T, Brustovetsky N, Hudmon A. Loss of calcium/calmodulin-dependent protein kinase II activity in cortical astrocytes decreases glutamate uptake and induces neurotoxic release of ATP. J Biol Chem 2013; 288:14599-14611. [PMID: 23543737 DOI: 10.1074/jbc.m113.466235] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The extent of calcium/calmodulin-dependent protein kinase II (CaMKII) inactivation in the brain after ischemia correlates with the extent of damage. We have previously shown that a loss of CaMKII activity in neurons is detrimental to neuronal viability by inducing excitotoxic glutamate release. In the current study we extend these findings to show that the ability of astrocytes to buffer extracellular glutamate is reduced when CaMKII is inhibited. Furthermore, CaMKII inhibition in astrocytes is associated with the rapid onset of intracellular calcium oscillations. Surprisingly, this rapid calcium influx is blocked by the N-type calcium channel antagonist, ω-conotoxin. Although the function of N-type calcium channels within astrocytes is controversial, these voltage-gated calcium channels have been linked to calcium-dependent vesicular gliotransmitter release. When extracellular glutamate and ATP levels are measured after CaMKII inhibition within our enriched astrocyte cultures, no alterations in glutamate levels are observed, whereas ATP levels in the extracellular environment significantly increase. Extracellular ATP accumulation associated with CaMKII inhibition contributes both to calcium oscillations within astrocytes and ultimately cortical neuron toxicity. Thus, a loss of CaMKII signaling within astrocytes dysregulates glutamate uptake and supports ATP release, two processes that would compromise neuronal survival after ischemic/excitotoxic insults.
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Affiliation(s)
- Nicole M Ashpole
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Aarti R Chawla
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Matthew P Martin
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Nickolay Brustovetsky
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202; Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Andy Hudmon
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202; Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202.
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17
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Brittain MK, Brustovetsky T, Brittain JM, Khanna R, Cummins TR, Brustovetsky N. Ifenprodil, a NR2B-selective antagonist of NMDA receptor, inhibits reverse Na+/Ca2+ exchanger in neurons. Neuropharmacology 2012; 63:974-82. [PMID: 22820271 DOI: 10.1016/j.neuropharm.2012.07.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 07/02/2012] [Accepted: 07/05/2012] [Indexed: 11/25/2022]
Abstract
Glutamate-induced delayed calcium dysregulation (DCD) is causally linked to excitotoxic neuronal death. The mechanisms of DCD are not completely understood, but it has been proposed that the excessive influx of external Ca(2+) is essential for DCD. The NMDA-subtype of glutamate receptor (NMDAR) and the plasmalemmal Na(+)/Ca(2+) exchanger operating in the reverse mode (NCX(rev)) have been implicated in DCD. In experiments with "younger" neurons, 6-8 days in vitro (6-8 DIV), in which the NR2A-containing NMDAR expression is low, ifenprodil, an inhibitor of NR2B-containing NMDAR, completely prevented DCD whereas PEAQX, another NMDAR antagonist that preferentially interacts with NR2A-NMDAR, was without effect. With "older" neurons (13-16 DIV), in which NR2A- and NR2B-NMDARs are expressed to a greater extent, both ifenprodil and PEAQX applied separately failed to prevent DCD. However, combined application of ifenprodil and PEAQX completely averted DCD. Ifenprodil and ifenprodil-like NR2B-NMDAR antagonists Ro 25-6981 and Co 101244 but not PEAQX or AP-5 inhibited gramicidin- and Na(+)/NMDG-replacement-induced increases in cytosolic Ca(2+) mediated predominantly by NCX(rev). This suggests that ifenprodil, Ro 25-6981, and Co 101244 inhibit NCX(rev). The ability of ifenprodil to inhibit NCX(rev) correlates with its efficacy in preventing DCD and emphasizes an important role of NCX(rev) in DCD. Overall our data suggest that both NR2A- and NR2B-NMDARs are involved in DCD in "older" neurons, and it is necessary to inhibit both NMDARs and NCX(rev) to prevent glutamate-induced DCD.
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Affiliation(s)
- Matthew K Brittain
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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18
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Kumar S, Chakraborty S, Barbosa C, Brustovetsky T, Brustovetsky N, Obukhov AG. Mechanisms controlling neurite outgrowth in a pheochromocytoma cell line: the role of TRPC channels. J Cell Physiol 2012; 227:1408-19. [PMID: 21618530 DOI: 10.1002/jcp.22855] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Transient Receptor Potential Canonical (TRPC) channels are implicated in modulating neurite outgrowth. The expression pattern of TRPCs changes significantly during brain development, suggesting that fine-tuning TRPC expression may be important for orchestrating neuritogenesis. To study how alterations in the TRPC expression pattern affect neurite outgrowth, we used nerve growth factor (NGF)-differentiated rat pheochromocytoma 12 (PC12) cells, a model system for neuritogenesis. In PC12 cells, NGF markedly up-regulated TRPC1 and TRPC6 expression, but down-regulated TRPC5 expression while promoting neurite outgrowth. Overexpression of TRPC1 augmented, whereas TRPC5 overexpression decelerated NGF-induced neurite outgrowth. Conversely, shRNA-mediated knockdown of TRPC1 decreased, whereas shRNA-mediated knockdown of TRPC5 increased NGF-induced neurite extension. Endogenous TRPC1 attenuated the anti-neuritogenic effect of overexpressed TRPC5 in part by forming the heteromeric TRPC1-TRPC5 channels. Previous reports suggested that TRPC6 may facilitate neurite outgrowth. However, we found that TRPC6 overexpression slowed down neuritogenesis, whereas dominant negative TRPC6 (DN-TRPC6) facilitated neurite outgrowth in NGF-differentiated PC12 cells. Consistent with these findings, hyperforin, a neurite outgrowth promoting factor, decreased TRPC6 expression in NGF-differentiated PC12 cells. Using pharmacological and molecular biological approaches, we determined that NGF up-regulated TRPC1 and TRPC6 expression via a p75(NTR)-IKK(2)-dependent pathway that did not involve TrkA receptor signaling in PC12 cells. Similarly, NGF up-regulated TRPC1 and TRPC6 via an IKK(2) dependent pathway in primary cultured hippocampal neurons. Thus, our data suggest that a balance of TRPC1, TRPC5, and TRPC6 expression determines neurite extension rate in neural cells, with TRPC6 emerging as an NGF-dependent "molecular damper" maintaining a submaximal velocity of neurite extension.
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Affiliation(s)
- Sanjay Kumar
- Department of Cellular and Integrative Physiology, IUPUI-Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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19
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Ashpole NM, Song W, Brustovetsky T, Engleman EA, Brustovetsky N, Cummins TR, Hudmon A. Calcium/calmodulin-dependent protein kinase II (CaMKII) inhibition induces neurotoxicity via dysregulation of glutamate/calcium signaling and hyperexcitability. J Biol Chem 2012; 287:8495-506. [PMID: 22253441 DOI: 10.1074/jbc.m111.323915] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Aberrant glutamate and calcium signalings are neurotoxic to specific neuronal populations. Calcium/calmodulin-dependent kinase II (CaMKII), a multifunctional serine/threonine protein kinase in neurons, is believed to regulate neurotransmission and synaptic plasticity in response to calcium signaling produced by neuronal activity. Importantly, several CaMKII substrates control neuronal structure, excitability, and plasticity. Here, we demonstrate that CaMKII inhibition for >4 h using small molecule and peptide inhibitors induces apoptosis in cultured cortical neurons. The neuronal death produced by prolonged CaMKII inhibition is associated with an increase in TUNEL staining and caspase-3 cleavage and is blocked with the translation inhibitor cycloheximide. Thus, this neurotoxicity is consistent with apoptotic mechanisms, a conclusion that is further supported by dysregulated calcium signaling with CaMKII inhibition. CaMKII inhibitory peptides also enhance the number of action potentials generated by a ramp depolarization, suggesting increased neuronal excitability with a loss of CaMKII activity. Extracellular glutamate concentrations are augmented with prolonged inhibition of CaMKII. Enzymatic buffering of extracellular glutamate and antagonism of the NMDA subtype of glutamate receptors prevent the calcium dysregulation and neurotoxicity associated with prolonged CaMKII inhibition. However, in the absence of CaMKII inhibition, elevated glutamate levels do not induce neurotoxicity, suggesting that a combination of CaMKII inhibition and elevated extracellular glutamate levels results in neuronal death. In sum, the loss of CaMKII observed with multiple pathological states in the central nervous system, including epilepsy, brain trauma, and ischemia, likely exacerbates programmed cell death by sensitizing vulnerable neuronal populations to excitotoxic glutamate signaling and inducing an excitotoxic insult itself.
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Affiliation(s)
- Nicole M Ashpole
- Stark Neuroscience Research Institute, Indiana University of School of Medicine, Indianapolis, Indiana 46202, USA
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Brittain MK, Brustovetsky T, Sheets PL, Brittain JM, Khanna R, Cummins TR, Brustovetsky N. Delayed calcium dysregulation in neurons requires both the NMDA receptor and the reverse Na+/Ca2+ exchanger. Neurobiol Dis 2012; 46:109-17. [PMID: 22249110 DOI: 10.1016/j.nbd.2011.12.051] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 12/12/2011] [Accepted: 12/31/2011] [Indexed: 12/20/2022] Open
Abstract
Glutamate-induced delayed calcium dysregulation (DCD) is a causal factor leading to neuronal death. The mechanism of DCD is not clear but Ca2+ influx via N-methyl-d-aspartate receptors (NMDAR) and/or the reverse plasmalemmal Na+/Ca2+ exchanger (NCXrev) could be involved in DCD. However, the extent to which NMDAR and NCX(rev) contribute to glutamate-induced DCD is uncertain. Here, we show that both NMDAR and NCX(rev) are critical for DCD in neurons exposed to excitotoxic glutamate. In rat cultured hippocampal neurons, 25 μM glutamate produced DCD accompanied by sustained increase in cytosolic Na+ ([Na+]c) and plasma membrane depolarization. MK801 and memantine, noncompetitive NMDAR inhibitors, added shortly after glutamate, completely prevented DCD whereas AP-5, a competitive NMDAR inhibitor, failed to protect against DCD. None of the tested inhibitors lowered elevated [Na+]c or restored plasma membrane potential. In the experiments with NCX reversal by gramicidin, MK801 and memantine robustly inhibited NCXrev while AP-5 was much less efficacious. In electrophysiological patch-clamp experiments MK801 and memantine inhibited NCXrev-mediated ion currents whereas AP-5 failed. Thus, MK801 and memantine, in addition to NMDAR, inhibited NCXrev. Inhibition of NCXrev either with KB-R7943, or by collapsing Na+ gradient across the plasma membrane, or by inhibiting Na+/H+ exchanger with 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and thus preventing the increase in [Na+]c failed to preclude DCD. However, NCXrev inhibition combined with NMDAR blockade by AP-5 completely prevented DCD. Overall, our data suggest that both NMDAR and NCXrev are essential for DCD in glutamate-exposed neurons and inhibition of individual mechanism is not sufficient to prevent calcium dysregulation.
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Affiliation(s)
- Matthew K Brittain
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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21
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Ashpole NM, Song W, Brustovetsky T, Brustovetsky N, Hudmon A. CaMKII Regulation of Calcium Homeostasis and Neuronal Activity. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.2789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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22
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Brittain JM, Pan R, You H, Brustovetsky T, Brustovetsky N, Zamponi GW, Lee WH, Khanna R. Disruption of NMDAR-CRMP-2 signaling protects against focal cerebral ischemic damage in the rat middle cerebral artery occlusion model. Channels (Austin) 2012; 6:52-9. [PMID: 22373559 DOI: 10.4161/chan.18919] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Collapsin response mediator protein 2 (CRMP-2), traditionally viewed as an axon/dendrite specification and axonal growth protein, has emerged as nidus in regulation of both pre- and post-synaptic Ca ( 2+) channels. Building on our discovery of the interaction and regulation of Ca ( 2+) channels by CRMP-2, we recently identified a short sequence in CRMP-2 which, when appended to the transduction domain of HIV TAT protein, suppressed acute, inflammatory and neuropathic pain in vivo by functionally uncoupling CRMP-2 from the Ca ( 2+) channel. Remarkably, we also found that this region attenuated Ca ( 2+) influx via N-methylD-Aspartate receptors (NMDARs) and reduced neuronal death in a moderate controlled cortical impact model of traumatic brain injury (TBI). Here, we sought to extend these findings by examining additional neuroprotective effects of this peptide (TAT-CBD3) and exploring the biochemical mechanisms by which TAT-CBD3 targets NMDARs. We observed that an intraperitoneal injection of TAT-CBD3 peptide significantly reduced infarct volume in an animal model of focal cerebral ischemia. Neuroprotection was observed when TAT-CBD3 peptide was given either prior to or after occlusion but just prior to reperfusion. Surprisingly, a direct biochemical complex was not resolvable between the NMDAR subunit NR2B and CRMP-2. Intracellular application of TAT-CBD3 failed to inhibit NMDAR current. NR2B interactions with the post synaptic density protein 95 (PSD-95) remained intact and were not disrupted by TAT-CBD3. Peptide tiling of intracellular regions of NR2B revealed two 15-mer sequences, in the carboxyl-terminus of NR2B, that may confer binding between NR2B and CRMP-2 which supports CRMP-2's role in excitotoxicity and neuroprotection.
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Affiliation(s)
- Joel M Brittain
- Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
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Brittain JM, Chen L, Wilson SM, Brustovetsky T, Gao X, Ashpole NM, Molosh AI, You H, Hudmon A, Shekhar A, White FA, Zamponi GW, Brustovetsky N, Chen J, Khanna R. Neuroprotection against traumatic brain injury by a peptide derived from the collapsin response mediator protein 2 (CRMP2). J Biol Chem 2011; 286:37778-92. [PMID: 21832084 PMCID: PMC3199520 DOI: 10.1074/jbc.m111.255455] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 08/05/2011] [Indexed: 11/06/2022] Open
Abstract
Neurological disabilities following traumatic brain injury (TBI) may be due to excitotoxic neuronal loss. The excitotoxic loss of neurons following TBI occurs largely due to hyperactivation of N-methyl-d-aspartate receptors (NMDARs), leading to toxic levels of intracellular Ca(2+). The axon guidance and outgrowth protein collapsin response mediator protein 2 (CRMP2) has been linked to NMDAR trafficking and may be involved in neuronal survival following excitotoxicity. Lentivirus-mediated CRMP2 knockdown or treatment with a CRMP2 peptide fused to HIV TAT protein (TAT-CBD3) blocked neuronal death following glutamate exposure probably via blunting toxicity from delayed calcium deregulation. Application of TAT-CBD3 attenuated postsynaptic NMDAR-mediated currents in cortical slices. In exploring modulation of NMDARs by TAT-CBD3, we found that TAT-CBD3 induced NR2B internalization in dendritic spines without altering somal NR2B surface expression. Furthermore, TAT-CBD3 reduced NMDA-mediated Ca(2+) influx and currents in cultured neurons. Systemic administration of TAT-CBD3 following a controlled cortical impact model of TBI decreased hippocampal neuronal death. These findings support TAT-CBD3 as a novel neuroprotective agent that may increase neuronal survival following injury by reducing surface expression of dendritic NR2B receptors.
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Affiliation(s)
- Joel M. Brittain
- From the Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute and
| | | | - Sarah M. Wilson
- From the Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute and
| | | | - Xiang Gao
- the Departments of Neurological Surgery
| | - Nicole M. Ashpole
- From the Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute and
- Biochemistry and Molecular Biology
| | | | - Haitao You
- the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Andy Hudmon
- From the Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute and
- Pharmacology and Toxicology
- Biochemistry and Molecular Biology
| | - Anantha Shekhar
- Psychiatry, and
- the Indiana Clinical and Translational Sciences Institute, and
| | - Fletcher A. White
- From the Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute and
- Anesthesia
- the Indiana Spinal Cord and Brain Injury Group, Indiana University School of Medicine, Indianapolis, Indiana 46202 and
| | - Gerald W. Zamponi
- the Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Nickolay Brustovetsky
- From the Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute and
- Pharmacology and Toxicology
| | - Jinhui Chen
- From the Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute and
- the Departments of Neurological Surgery
- the Indiana Spinal Cord and Brain Injury Group, Indiana University School of Medicine, Indianapolis, Indiana 46202 and
| | - Rajesh Khanna
- From the Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute and
- Pharmacology and Toxicology
- the Indiana Spinal Cord and Brain Injury Group, Indiana University School of Medicine, Indianapolis, Indiana 46202 and
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Brittain JM, Duarte DB, Wilson SM, Zhu W, Ballard C, Johnson PL, Liu N, Xiong W, Ripsch MS, Wang Y, Fehrenbacher JC, Fitz SD, Khanna M, Park CK, Schmutzler BS, Cheon BM, Due MR, Brustovetsky T, Ashpole NM, Hudmon A, Meroueh SO, Hingtgen CM, Brustovetsky N, Ji RR, Hurley JH, Jin X, Shekhar A, Xu XM, Oxford GS, Vasko MR, White FA, Khanna R. Suppression of inflammatory and neuropathic pain by uncoupling CRMP-2 from the presynaptic Ca²⁺ channel complex. Nat Med 2011; 17:822-9. [PMID: 21642979 DOI: 10.1038/nm.2345] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 03/07/2011] [Indexed: 11/09/2022]
Abstract
The use of N-type voltage-gated calcium channel (CaV2.2) blockers to treat pain is limited by many physiological side effects. Here we report that inflammatory and neuropathic hypersensitivity can be suppressed by inhibiting the binding of collapsin response mediator protein 2 (CRMP-2) to CaV2.2 and thereby reducing channel function. A peptide of CRMP-2 fused to the HIV transactivator of transcription (TAT) protein (TAT-CBD3) decreased neuropeptide release from sensory neurons and excitatory synaptic transmission in dorsal horn neurons, reduced meningeal blood flow, reduced nocifensive behavior induced by formalin injection or corneal capsaicin application and reversed neuropathic hypersensitivity produced by an antiretroviral drug. TAT-CBD3 was mildly anxiolytic without affecting memory retrieval, sensorimotor function or depression. At doses tenfold higher than that required to reduce hypersensitivity in vivo, TAT-CBD3 caused a transient episode of tail kinking and body contortion. By preventing CRMP-2-mediated enhancement of CaV2.2 function, TAT-CBD3 alleviated inflammatory and neuropathic hypersensitivity, an approach that may prove useful in managing chronic pain.
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Affiliation(s)
- Joel M Brittain
- Program in Medical Neurosciences, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana, USA
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Brustovetsky T, Brittain MK, Sheets PL, Cummins TR, Pinelis V, Brustovetsky N. KB-R7943, an inhibitor of the reverse Na+ /Ca2+ exchanger, blocks N-methyl-D-aspartate receptor and inhibits mitochondrial complex I. Br J Pharmacol 2011; 162:255-70. [PMID: 20883473 DOI: 10.1111/j.1476-5381.2010.01054.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE An isothiourea derivative (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methane sulfonate (KB-R7943), a widely used inhibitor of the reverse Na(+) /Ca(2+) exchanger (NCX(rev)), was instrumental in establishing the role of NCX(rev) in glutamate-induced Ca(2+) deregulation in neurons. Here, the effects of KB-R7943 on N-methyl-D-aspartate (NMDA) receptors and mitochondrial complex I were tested. EXPERIMENTAL APPROACH Fluorescence microscopy, electrophysiological patch-clamp techniques and cellular respirometry with Seahorse XF24 analyzer were used with cultured hippocampal neurons; membrane potential imaging, respirometry and Ca(2+) flux measurements were made in isolated rat brain mitochondria. KEY RESULTS KB-R7943 inhibited NCX(rev) with IC(50) = 5.7 ± 2.1 µM, blocked NMDAR-mediated ion currents, and inhibited NMDA-induced increase in cytosolic Ca(2+) with IC(50) = 13.4 ± 3.6 µM but accelerated calcium deregulation and mitochondrial depolarization in glutamate-treated neurons. KB-R7943 depolarized mitochondria in a Ca(2+) -independent manner. Stimulation of NMDA receptors caused NAD(P)H oxidation that was coupled or uncoupled from ATP synthesis depending on the presence of Ca(2+) in the bath solution. KB-R7943, or rotenone, increased NAD(P)H autofluorescence under resting conditions and suppressed NAD(P)H oxidation following glutamate application. KB-R7943 inhibited 2,4-dinitrophenol-stimulated respiration of cultured neurons with IC(50) = 11.4 ± 2.4 µM. With isolated brain mitochondria, KB-R7943 inhibited respiration, depolarized organelles and suppressed Ca(2+) uptake when mitochondria oxidized complex I substrates but was ineffective when mitochondria were supplied with succinate, a complex II substrate. CONCLUSIONS AND IMPLICATIONS KB-R7943, in addition to NCX(rev) , blocked NMDA receptors in cultured hippocampal neurons and inhibited complex I in the mitochondrial respiratory chain. These findings are critical for the correct interpretation of experimental results obtained with KB-R7943 and a better understanding of its neuroprotective action.
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Affiliation(s)
- Tatiana Brustovetsky
- Department of Pharmacology and Toxicology Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA.
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Brustovetsky T, Li T, Yang Y, Zhang JT, Antonsson B, Brustovetsky N. BAX insertion, oligomerization, and outer membrane permeabilization in brain mitochondria: role of permeability transition and SH-redox regulation. Biochim Biophys Acta 2010; 1797:1795-806. [PMID: 20655869 PMCID: PMC2933961 DOI: 10.1016/j.bbabio.2010.07.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 07/05/2010] [Accepted: 07/11/2010] [Indexed: 10/19/2022]
Abstract
BAX cooperates with truncated BID (tBID) and Ca(2+) in permeabilizing the outer mitochondrial membrane (OMM) and releasing mitochondrial apoptogenic proteins. The mechanisms of this cooperation are still unclear. Here we show that in isolated brain mitochondria, recombinant BAX readily self-integrates/oligomerizes in the OMM but produces only a minuscule release of cytochrome c, indicating that BAX insertion/oligomerization in the OMM does not always lead to massive OMM permeabilization. Ca(2+) in a mitochondrial permeability transition (mPT)-dependent and recombinant tBID in an mPT-independent manner promoted BAX insertion/ oligomerization in the OMM and augmented cytochrome c release. Neither tBID nor Ca(2+) induced BAX oligomerization in the solution without mitochondria, suggesting that BAX oligomerization required interaction with the organelles and followed rather than preceded BAX insertion in the OMM. Recombinant Bcl-xL failed to prevent BAX insertion/oligomerization in the OMM but strongly attenuated cytochrome c release. On the other hand, a reducing agent, dithiothreitol (DTT), inhibited BAX insertion/oligomerization augmented by tBID or Ca(2+) and suppressed the BAX-mediated release of cytochrome c and Smac/DIABLO but failed to inhibit Ca(2+)-induced swelling. Altogether, these data suggest that in brain mitochondria, BAX insertion/oligomerization can be dissociated from OMM permeabilization and that tBID and Ca(2+) stimulate BAX insertion/oligomerization and BAX-mediated OMM permeabilization by different mechanisms involving mPT induction and modulation of the SH-redox state.
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Affiliation(s)
- Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Tsyregma Li
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Youyun Yang
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
- Simon Cancer Center, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Jiang-Ting Zhang
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
- Simon Cancer Center, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | | | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis IN 46202, USA
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Brustovetsky T, Bolshakov A, Brustovetsky N. Calpain activation and Na+/Ca2+ exchanger degradation occur downstream of calcium deregulation in hippocampal neurons exposed to excitotoxic glutamate. J Neurosci Res 2010; 88:1317-28. [PMID: 19937813 PMCID: PMC2830319 DOI: 10.1002/jnr.22295] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Delayed calcium deregulation (DCD) plays an essential role in glutamate excitotoxicity, a major detrimental factor in stroke, traumatic brain injury, and various neurodegenerations. In the present study, we examined the role of calpain activation and Na(+)/Ca(2+) exchanger (NCX) degradation in DCD and excitotoxic cell death in cultured hippocampal neurons. Exposure of neurons to glutamate caused DCD accompanied by secondary mitochondrial depolarization. Activation of calpain was evidenced by detecting NCX isoform 3 (NCX3) degradation products. Degradation of NCX isoform 1 (NCX1) was below the detection limit of Western blotting. Degradation of NCX3 was detected only after 1 hr of incubation with glutamate, whereas DCD occurred on average within 15 min after glutamate application. Calpeptin, an inhibitor of calpain, significantly attenuated NCX3 degradation but failed to inhibit DCD and excitotoxic neuronal death. Calpain inhibitors I, III, and VI also failed to influence DCD and glutamate-induced neuronal death. On the other hand, MK801, an inhibitor of the NMDA subtype of glutamate receptors, added shortly after the initial glutamate-induced jump in cytosolic Ca(2+), completely prevented DCD and activation of calpain and strongly protected neurons against excitotoxicity. Taken together, our results suggest that, in glutamate-treated hippocampal neurons, the initial increase in cytosolic Ca(2+) that precedes DCD is insufficient for sustained calpain activation, which most likely occurs downstream of DCD.
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Affiliation(s)
- Tatiana Brustovetsky
- Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Alexey Bolshakov
- Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Storozhevykh TP, Senilova YE, Brustovetsky T, Pinelis VG, Brustovetsky N. Neuroprotective Effect of KB-R7943 Against Glutamate Excitotoxicity is Related to Mild Mitochondrial Depolarization. Neurochem Res 2009; 35:323-35. [DOI: 10.1007/s11064-009-0058-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/29/2009] [Indexed: 01/08/2023]
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Li V, Brustovetsky T, Brustovetsky N. Role of cyclophilin D-dependent mitochondrial permeability transition in glutamate-induced calcium deregulation and excitotoxic neuronal death. Exp Neurol 2009; 218:171-82. [PMID: 19236863 PMCID: PMC2710407 DOI: 10.1016/j.expneurol.2009.02.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Revised: 02/05/2009] [Accepted: 02/07/2009] [Indexed: 11/29/2022]
Abstract
In the present study we tested the hypothesis that the cyclophilin D-dependent (CyD) mitochondrial permeability transition (CyD-mPT) plays an important role in glutamate-triggered delayed calcium deregulation (DCD) and excitotoxic neuronal death. We used cultured cortical neurons from wild-type C57BL/6 and cyclophilin D-knockout mice (Ppif(-/-)). Induction of the mPT was identified by following the rapid secondary acidification of mitochondrial matrices monitored with mitochondrially targeted pH-sensitive yellow fluorescent protein. Suppression of the CyD-mPT due to genetic CyD ablation deferred DCD and mitochondrial depolarization, and increased the survival rate after exposure of neurons to 10 microM glutamate, but not to 100 microM glutamate. Ca(2+) influx into Ppif(-/-) neurons was not diminished in comparison with WT neurons judging by (45)Ca accumulation. In both types of neurons, 100 microM glutamate produced greater Ca(2+) influx than 10 microM glutamate. We hypothesize that greater Ca(2+) influx produced by higher glutamate rapidly triggered the CyD-independent mPT in both WT and Ppif(-/-) neurons equalizing their responses to supra-physiologic excitotoxic insults. In neurons exposed to moderate but pathophysiologically-relevant glutamate concentrations, an induction of the CyD-mPT appears to play an important role in mitochondrial injury contributing to DCD and cell death.
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Affiliation(s)
- Viacheslav Li
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis IN 46202, USA
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Li T, Brustovetsky T, Antonsson B, Brustovetsky N. Oligomeric BAX induces mitochondrial permeability transition and complete cytochrome c release without oxidative stress. Biochim Biophys Acta 2008; 1777:1409-21. [PMID: 18771651 PMCID: PMC2613194 DOI: 10.1016/j.bbabio.2008.08.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 08/07/2008] [Accepted: 08/08/2008] [Indexed: 01/26/2023]
Abstract
In the present study, we investigated the mechanism of cytochrome c release from isolated brain mitochondria induced by recombinant oligomeric BAX (BAX(oligo)). We found that BAX(oligo) caused a complete release of cytochrome c in a concentration- and time-dependent manner. The release was similar to those induced by alamethicin, which causes maximal mitochondrial swelling and eliminates barrier properties of the OMM. BAX(oligo) also produced large amplitude mitochondrial swelling as judged by light scattering assay and transmission electron microscopy. In addition, BAX(oligo) resulted in a strong mitochondrial depolarization. ATP or a combination of cyclosporin A and ADP, inhibitors of the mPT, suppressed BAX(oligo)-induced mitochondrial swelling and depolarization as well as cytochrome c release but did not influence BAX(oligo) insertion into the OMM. Both BAX(oligo)- and alamethicin-induced cytochrome c releases were accompanied by inhibition of ROS generation, which was assessed by measuring mitochondrial H(2)O(2) release with an Amplex Red assay. The mPT inhibitors antagonized suppression of ROS generation caused by BAX(oligo) but not by alamethicin. Thus, BAX(oligo) resulted in a complete cytochrome c release from isolated brain mitochondria in the mPT-dependent manner without involvement of oxidative stress by the mechanism requiring mitochondrial remodeling and permeabilization of the OMM.
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Affiliation(s)
- Tsyregma Li
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Bruno Antonsson
- Geneva Research Center, Merck Serono International, Geneva, Switzerland
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis IN 46202, USA
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis IN 46202, USA
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Shalbuyeva N, Brustovetsky T, Brustovetsky N. Lithium desensitizes brain mitochondria to calcium, antagonizes permeability transition, and diminishes cytochrome C release. J Biol Chem 2007; 282:18057-18068. [PMID: 17485418 DOI: 10.1074/jbc.m702134200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Among the numerous effects of lithium on intracellular targets, its possible action on mitochondria remains poorly explored. In the experiments with suspension of isolated brain mitochondria, replacement of KCl by LiCl suppressed mitochondrial swelling, depolarization, and a release of cytochrome c induced by a single Ca2+ bolus. Li+ robustly protected individual brain mitochondria loaded with rhodamine 123 against Ca2+-induced depolarization. In the experiments with slow calcium infusion, replacement of KCl by LiCl in the incubation medium increased resilience of synaptic and nonsynaptic brain mitochondria as well as resilience of liver and heart mitochondria to the deleterious effect of Ca2+. In LiCl medium, mitochondria accumulated larger amounts of Ca2+ before they lost the ability to sequester Ca2+. However, lithium appeared to be ineffective if mitochondria were challenged by Sr2+ instead of Ca2+. Cyclosporin A, sanglifehrin A, and Mg2+, inhibitors of the mitochondrial permeability transition (mPT), increased mitochondrial Ca2+ capacity in KCl medium but failed to do so in LiCl medium. This suggests that the mPT might be a common target for Li+ and mPT inhibitors. In addition, lithium protected mitochondria against high Ca2+ in the presence of ATP, where cyclosporin A was reported to be ineffective. SB216763 and SB415286, inhibitors of glycogen synthase kinase-3beta, which is implicated in regulating reactive oxygen species-induced mPT in cardiac mitochondria, did not increase Ca2+ capacity of brain mitochondria. Altogether, these findings suggest that Li+ desensitizes mitochondria to elevated Ca2+ and diminishes cytochrome c release from brain mitochondria by antagonizing the Ca2+-induced mPT.
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Affiliation(s)
- Natalia Shalbuyeva
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Nickolay Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202; Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202.
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Abstract
An exposure of cultured hippocampal neurons expressing mitochondrially targeted enhanced yellow fluorescent protein to excitotoxic glutamate resulted in reversible mitochondrial remodeling that in many instances could be interpreted as swelling. Remodeling was not evident if glutamate receptors were blocked with MK801, if Ca(2+) was omitted or substituted for Sr(2+) in the bath solution, if neurons were treated with carbonylcyanide p-trifluoromethoxyphenylhydrazone to depolarize mitochondria, or if neurons were pretreated with cyclosporin A or N-methyl-4-isoleucine-cyclosporin (NIM811) to inhibit the mitochondrial permeability transition. In the experiments with isolated brain synaptic or nonsynaptic mitochondria, Ca(2+) triggered transient, spontaneously reversible cyclosporin A-sensitive swelling closely resembling remodeling of organelles in cultured neurons. The swelling was accompanied by the release of cytochrome c, Smac/DIABLO, Omi/HtrA2, and AIF but not endonuclease G. Depolarization with carbonylcyanide p-trifluoromethoxyphenylhydrazone or inhibition of the Ca(2+) uniporter with Ru360 prevented rapid onset of the swelling. Sr(2+) depolarized mitochondria but failed to induce swelling. Neither inhibitors of the large conductance Ca(2+)-activated K(+) channel (charybdotoxin, iberiotoxin, quinine, and Ba(2+)) nor inhibitors of the mitochondrial ATP-sensitive K(+) channel (5-hydroxydecanoate and glibenclamide) suppressed swelling. Quinine, dicyclohexylcarbodiimide, and Mg(2+), inhibitors of the mitochondrial K(+)/H(+) exchanger, as well as external alkalization inhibited a recovery phase of the reversible swelling. In contrast to brain mitochondria, liver and heart mitochondria challenged with Ca(2+) experienced sustained swelling without spontaneous recovery. The proposed model suggests an involvement of the Ca(2+)-dependent transient K(+) influx into the matrix causing mitochondrial swelling followed by activation of the K(+)/H(+) exchanger leading to spontaneous mitochondrial contraction both in situ and in vitro.
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Affiliation(s)
- Natalia Shalbuyeva
- Department of Pharmacology and Toxicology, Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Brustovetsky N, LaFrance R, Purl KJ, Brustovetsky T, Keene CD, Low WC, Dubinsky JM. Age-dependent changes in the calcium sensitivity of striatal mitochondria in mouse models of Huntington's Disease. J Neurochem 2005; 93:1361-70. [PMID: 15935052 DOI: 10.1111/j.1471-4159.2005.03036.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Striatal and cortical mitochondria from knock-in and transgenic mutant huntingtin mice were examined for their sensitivity to calcium induction of the permeability transition, a cause of mitochondrial depolarization and ATP loss. The permeability transition has been suggested to contribute to cell death in Huntington's Disease. Mitochondria were examined from slowly progressing knock-in mouse models with different length polyglutarnine expansions (Q20, Q50, Q92, Q111) and from the rapidly progressing transgenic R6/2 mice overexpressing exon I of human huntingtin with more than 110 polyglutamines. As previously observed in rats, striatal mitochondria from background strain CD1 and C57BL/6 control mice were more sensitive to calcium than cortical mitochondria. Between 5 and 12 months in knock-in Q92 mice and between 8 and 12 weeks in knock-in Q111 mice, striatal mitochondria developed resistance, becoming equally sensitive to calcium as cortical mitochondria, while those from Q50 mice were unchanged. Cortical mitochondrial calcium sensitivity did not change. In R6/2 mice striatal and cortical mitochondria were equally resistant to Ca2+ while striatal mitochondria from littermate controls were more susceptible. No increases in calcium sensitivity were observed in the mitochondria from Huntington's Disease (HD) mice compared to controls. Neither motor abnormalities, nor expression of cyclophilin D corresponded to the changes in mitochondrial sensitivity. Polyglutamine expansions in huntingtin produced an early increased resistance to calcium in striatal mitochondria suggesting mitochondria undergo compensatory changes in calcium sensitivity in response to the many cellular changes wrought by polyglutamine expansion.
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Affiliation(s)
- N Brustovetsky
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Brustovetsky T, Shalbuyeva N, Brustovetsky N. Lack of manifestations of diazoxide/5-hydroxydecanoate-sensitive KATP channel in rat brain nonsynaptosomal mitochondria. J Physiol 2005; 568:47-59. [PMID: 16051627 PMCID: PMC1474777 DOI: 10.1113/jphysiol.2005.091199] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Pharmacological modulation of the mitochondrial ATP-sensitive K+ channel (mitoKATP) sensitive to diazoxide and 5-hydroxydecanoate (5-HD) represents an attractive strategy to protect cells against ischaemia/reperfusion- and stroke-related injury. To re-evaluate a functional role for the mitoKATP in brain, we used Percoll-gradient-purified brain nonsynaptosomal mitochondria in a light absorbance assay, in radioisotope measurements of matrix volume, and in measurements of respiration, membrane potential (DeltaPsi) and depolarization-induced K+ efflux. The changes in mitochondrial morphology were evaluated by transmission electron microscopy (TEM). Polyclonal antibodies raised against certain fragments of known sulphonylurea receptor subunits, SUR1 and SUR2, and against different epitopes of K+ inward rectifier subunits Kir 6.1 and Kir 6.2 of the ATP-sensitive K+ channel of the plasma membrane (cellKATP), were employed to detect similar subunits in brain mitochondria. A variety of plausible blockers (ATP, 5-hydroxydecanoate, glibenclamide, tetraphenylphosphonium cation) and openers (diazoxide, pinacidil, chromakalim, minoxidil, testosterone) of the putative mitoKATP were applied to show the role of the channel in regulating matrix volume, respiration, and DeltaPsi and K+ fluxes across the inner mitochondrial membrane. None of the pharmacological agents applied to brain mitochondria in the various assays pinpointed processes that could be unequivocally associated with mitoKATP activity. In addition, immunoblotting analysis did not provide explicit evidence for the presence of the mitoKATP, similar to the cellKATP, in brain mitochondria. On the other hand, the depolarization-evoked release of K+ suppressed by ATP could be re-activated by carboxyatractyloside, an inhibitor of the adenine nucleotide translocase (ANT). Moreover, bongkrekic acid, another inhibitor of the ANT, inhibited K+ efflux similarly to ATP. These observations implicate the ANT in ATP-sensitive K+ transport in brain mitochondria.
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Affiliation(s)
- Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Dr., Medical Science Building 549, Indianapolis, IN 46202, USA
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Brustovetsky T, Antonsson B, Jemmerson R, Dubinsky JM, Brustovetsky N. Activation of calcium-independent phospholipase A2 (iPLA2) in brain mitochondria and release of apoptogenic factors by BAX and truncated BID. J Neurochem 2005; 94:980-94. [PMID: 16092941 DOI: 10.1111/j.1471-4159.2005.03248.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cleaved or truncated BID (tBID) is known to oligomerize both BAK and BAX. Previously, BAK and BAX lacing the C-terminal fragment (BAXDeltaC) were shown to induce modest cytochrome c (Cyt c) release from rat brain mitochondria when activated by tBID. We now show that tBID plus monomeric full-length BAX induce extensive release of Cyt c, Smac/DIABLO, and Omi/HtrA2 (but not endonuclease G and the apoptosis inducing factor) comparable to the release induced by alamethicin. This occurs independently of the permeability transition without overt changes in mitochondrial morphology. The mechanism of the release may involve formation of reactive oxygen species (ROS) and activation of calcium-independent phospholipase A(2) (iPLA(2)). Indeed, increased ROS production and activated iPLA(2) were observed prior to massive Cyt c release. Furthermore, the extent of inhibition of Cyt c release correlated with the degree of suppression of iPLA(2) by the inhibitors propranolol, dibucaine, 4-bromophenacyl bromide, and bromenol lactone. Consistent with a requirement for iPLA(2) in Cyt c release from brain mitochondria, synthetic liposomes composed of lipids mimicking the outer mitochondrial membrane (OMM) but lacing iPLA(2) failed to release 10 kDa fluorescent dextran (FD-10) in response to tBID plus BAX. We propose that tBID plus BAX activate ROS generation, which subsequently augments iPLA(2) activity leading to changes in the OMM that allow translocation of certain mitochondrial proteins from the intermembrane space.
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Affiliation(s)
- Tatiana Brustovetsky
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Brustovetsky T, Purl K, Young A, Shimizu K, Dubinsky JM. Dearth of glutamate transporters contributes to striatal excitotoxicity. Exp Neurol 2004; 189:222-30. [PMID: 15380474 DOI: 10.1016/j.expneurol.2004.03.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2003] [Revised: 02/11/2004] [Accepted: 03/29/2004] [Indexed: 10/26/2022]
Abstract
Since excitotoxicity is hypothesized to contribute to cell death in Huntington's disease (HD), we examined the susceptibility of striatal and hippocampal neurons to glutamate-induced cell death. Striatal cultures were more susceptible to glutamate-triggered toxicity than sister hippocampal cultures. Dose-response curves were equivalent when secondary toxicity was blocked with application of the NMDA receptor antagonist, MK801, or enhanced with the pan-specific glutamate transport blocker, TBOA, following excitotoxin removal. TBOA failed to alter the dose-response characteristics of striatal excitotoxicity, ruling out reverse operation of glutamate transporters. Striatal cultures expressed less EAAC1 and less membrane-associated EAAC1, GLT1, and GLAST than hippocampal cultures. Antisense down-regulation of EAAC1 increased the sensitivity of hippocampal cultures to glutamate, indicating that this transporter can act as an important neuroprotectant. Thus, the relative expression levels of glutamate transporters, even in parts of the brain where they are considered adequately expressed, appear to influence the sensitivities of different neuronal populations to excitotoxicity.
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Brustovetsky N, Brustovetsky T, Purl KJ, Capano M, Crompton M, Dubinsky JM. Increased susceptibility of striatal mitochondria to calcium-induced permeability transition. J Neurosci 2003; 23:4858-67. [PMID: 12832508 PMCID: PMC6741171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2003] [Revised: 03/24/2003] [Accepted: 03/26/2003] [Indexed: 03/03/2023] Open
Abstract
Mitochondria were simultaneously isolated from striatum and cortex of adult rats and compared in functional assays for their sensitivity to calcium activation of the permeability transition. Striatal mitochondria showed an increased dose-dependent sensitivity to Ca2+ compared with cortical mitochondria, as measured by mitochondrial depolarization, swelling, Ca2+ uptake, reactive oxygen species production, and respiration. Ratios of ATP to ADP were lower in striatal mitochondria exposed to calcium despite equal amounts of ADP and ATP under respiring and nonrespiring conditions. The Ca2+-induced changes were inhibited by cyclosporin A or ADP. These responses are consistent with Ca2+ activation of both low and high permeability pathways constituting the mitochondrial permeability transition. In addition to the striatal supersensitivity to induction of the permeability transition, cyclosporin A inhibition was less potent in striatal mitochondria. Immunoblots indicated that striatal mitochondria contained more cyclophilin D than cortical mitochondria. Thus striatal mitochondria may be selectively vulnerable to the permeability transition. Subsequent mitochondrial dysfunction could contribute to the initial toxicity of striatal neurons in Huntington's disease.
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Affiliation(s)
- Nickolay Brustovetsky
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Brustovetsky N, Brustovetsky T, Jemmerson R, Dubinsky JM. Calcium-induced cytochrome c release from CNS mitochondria is associated with the permeability transition and rupture of the outer membrane. J Neurochem 2002; 80:207-18. [PMID: 11902111 DOI: 10.1046/j.0022-3042.2001.00671.x] [Citation(s) in RCA: 184] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The mechanisms of Ca2+-induced release of Cytochrome c (Cyt c) from rat brain mitochondria were examined quantitatively using a capture ELISA. In 75 or 125 mm KCl-based media 1.4 micromol Ca2+/mg protein caused depolarization and mitochondrial swelling. However, this resulted in partial Cyt c release only in 75 mm KCl. The release was inhibited by Ru360, an inhibitor of the Ca2+ uniporter, and by cyclosporin A plus ADP, a combination of mitochondrial permeability transition inhibitors. Transmission electron microscopy (TEM) revealed that Ca2+-induced swelling caused rupture of the outer membrane only in 75 mm KCl. Koenig's polyanion, an inhibitor of mitochondrial porin (VDAC), enhanced swelling and amplified Cyt c release. Dextran T70 that is known to enhance mitochondrial contact site formation did not prevent Cyt c release. Exposure of cultured cortical neurons to 500 microM glutamate for 5 min caused Cyt c release into the cytosol 30 min after glutamate removal. MK-801 or CsA inhibited this release. Thus, the release of Cyt c from CNS mitochondria induced by Ca2+ in vitro as well as in situ involved the mPT and appeared to require the rupture of the outer membrane.
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Abstract
Creatine and phosphocreatine were evaluated for their ability to prevent death of cultured striatal and hippocampal neurons exposed to either glutamate or 3-nitropropionic acid (3NP) and to inhibit the mitochondrial permeability transition in CNS mitochondria. Phosphocreatine (PCr), and to a lesser extent creatine (Cr), but not (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK801), dose-dependently ameliorated 3NP toxicity when applied simultaneously with the 3NP in Mg2+-free media. Pre-treatment of PCr for 2 or 5 days and Cr for 5 days protected against glutamate excitotoxicity equivalent to that achieved by MK801 post-treatment. The combination of PCr or Cr pre-treatment and MK801 post-treatment did not provide additional protection, indicating that both prevented the toxicity attributable to secondary glutamate release. To determine if Cr or PCr directly inhibited the permeability transition, mitochondrial swelling and depolarization were assayed in isolated, purified brain mitochondria. PCr reduced the amount of swelling induced by calcium by 20%. Cr decreased mitochondrial swelling when inhibitors of creatine kinase octamer-dimer transition were present. However, in brain mitochondria prepared from rats fed a diet supplemented with 2% creatine for 2 weeks, the extent of calcium-induced mitochondrial swelling was not altered. Thus, the neuroprotective properties of PCr and Cr may reflect enhancement of cytoplasmic high-energy phosphates but not permeability transition inhibition.
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Affiliation(s)
- N Brustovetsky
- Department of Neuroscience, University of Minnesota, Minneapolis 55455, USA
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