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Sung U, Binda F, Savchenko V, Owens WA, Daws LC. Ca 2+ dependent surface trafficking of norepinephrine transporters depends on threonine 30 and Ca 2+ calmodulin kinases. J Chem Neuroanat 2016; 83-84:19-35. [PMID: 28017803 DOI: 10.1016/j.jchemneu.2016.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 12/09/2016] [Accepted: 12/15/2016] [Indexed: 11/28/2022]
Abstract
The antidepressant-sensitive norepinephrine (NE) transporter (NET) inactivates NE released during central and peripheral neuronal activity by transport into presynaptic cells. Altered NE clearance due to dysfunction of NET has been associated with the development of mental illness and cardiovascular diseases. NET activity in vivo is influenced by stress, neuronal activity, hormones and drugs. We investigated the mechanisms of Ca2+ regulation of NET and found that Ca2+ influenced both Vmax and Km for NE transport into cortical synaptosomes. Changes in extracellular Ca2+ triggered rapid and bidirectional surface trafficking of NET expressed in cultured cells. Deletion of residues 28-47 in the NET NH2-terminus abolished the Ca2+ effect on surface trafficking. Mutagenesis studies identified Thr30 in this region as the essential residue for both Ca2+- dependent phosphorylation and trafficking of NET. Depolarization of excitable cells increased surface NET in a Thr30 dependent manner. A proteomic analysis, RNA interference, and pharmacological inhibition supported roles of CaMKI and CaMKII in Ca2+-modulated NE transport and NET trafficking. Depolarization of primary noradrenergic neurons in culture with elevated K+ increased NET surface expression in a process that required external Ca2+ and depended on CaMK activity. Hippocampal NE clearance in vivo was also stimulated by depolarization, and inhibitors of CaMK signaling prevented this stimulation. In summary, Ca2+ signaling influenced surface trafficking of NET through a CaMK-dependent mechanism requiring Thr30.
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Affiliation(s)
- Uhna Sung
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232-8548, United States.
| | - Francesca Binda
- Institute of Cellular and Integrative Neurosciences, CNRS, Strasbourg, France
| | - Valentina Savchenko
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232-8548, United States
| | - William A Owens
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, United States
| | - Lynette C Daws
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, United States.
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2
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Souza IA, Gandini MA, Wan MM, Zamponi GW. Two heterozygous Cav3.2 channel mutations in a pediatric chronic pain patient: recording condition-dependent biophysical effects. Pflugers Arch 2015; 468:635-42. [DOI: 10.1007/s00424-015-1776-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Revised: 12/14/2015] [Accepted: 12/16/2015] [Indexed: 11/24/2022]
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3
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Torregrosa R, Yang XF, Dustrude ET, Cummins TR, Khanna R, Kohn H. Chimeric derivatives of functionalized amino acids and α-aminoamides: compounds with anticonvulsant activity in seizure models and inhibitory actions on central, peripheral, and cardiac isoforms of voltage-gated sodium channels. Bioorg Med Chem 2015; 23:3655-66. [PMID: 25922183 PMCID: PMC4461516 DOI: 10.1016/j.bmc.2015.04.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 03/26/2015] [Accepted: 04/03/2015] [Indexed: 10/23/2022]
Abstract
Six novel 3″-substituted (R)-N-(phenoxybenzyl) 2-N-acetamido-3-methoxypropionamides were prepared and then assessed using whole-cell, patch-clamp electrophysiology for their anticonvulsant activities in animal seizure models and for their sodium channel activities. We found compounds with various substituents at the terminal aromatic ring that had excellent anticonvulsant activity. Of these compounds, (R)-N-4'-((3″-chloro)phenoxy)benzyl 2-N-acetamido-3-methoxypropionamide ((R)-5) and (R)-N-4'-((3″-trifluoromethoxy)phenoxy)benzyl 2-N-acetamido-3-methoxypropionamide ((R)-9) exhibited high protective indices (PI=TD50/ED50) comparable with many antiseizure drugs when tested in the maximal electroshock seizure test to mice (intraperitoneally) and rats (intraperitoneally, orally). Most compounds potently transitioned sodium channels to the slow-inactivated state when evaluated in rat embryonic cortical neurons. Treating HEK293 recombinant cells that expressed hNaV1.1, rNaV1.3, hNaV1.5, or hNaV1.7 with (R)-9 recapitulated the high levels of sodium channel slow inactivation.
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Affiliation(s)
- Robert Torregrosa
- NeuroGate Therapeutics, Inc., 150 Fayetteville Street, Suite 2300, Raleigh, NC 27601, United States
| | - Xiao-Fang Yang
- Department of Pharmacology and Neuroscience Graduate Interdisciplinary Program, College of Medicine, University of Arizona, Tucson, AZ 85742, United States
| | - Erik T Dustrude
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, United States
| | - Theodore R Cummins
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, United States; Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, United States
| | - Rajesh Khanna
- Department of Pharmacology and Neuroscience Graduate Interdisciplinary Program, College of Medicine, University of Arizona, Tucson, AZ 85742, United States
| | - Harold Kohn
- NeuroGate Therapeutics, Inc., 150 Fayetteville Street, Suite 2300, Raleigh, NC 27601, United States; Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, United States; Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, United States
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4
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Park KD, Yang XF, Dustrude ET, Wang Y, Ripsch MS, White FA, Khanna R, Kohn H. Chimeric agents derived from the functionalized amino acid, lacosamide, and the α-aminoamide, safinamide: evaluation of their inhibitory actions on voltage-gated sodium channels, and antiseizure and antinociception activities and comparison with lacosamide and safinamide. ACS Chem Neurosci 2015; 6:316-30. [PMID: 25418676 PMCID: PMC4372064 DOI: 10.1021/cn5002182] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
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The functionalized amino acid, lacosamide
((R)-2), and the α-aminoamide,
safinamide ((S)-3), are neurological
agents that have been extensively
investigated and have displayed potent anticonvulsant activities in
seizure models. Both compounds have been reported to modulate voltage-gated
sodium channel activity. We have prepared a series of chimeric compounds,
(R)-7–(R)-10, by merging key structural units in these two clinical
agents, and then compared their activities with (R)-2 and (S)-3. Compounds
were assessed for their ability to alter sodium channel kinetics for
inactivation, frequency (use)-dependence, and steady-state activation
and fast inactivation. We report that chimeric compounds (R)-7–(R)-10 in catecholamine A-differentiated (CAD) cells and embryonic rat
cortical neurons robustly enhanced sodium channel inactivation at
concentrations far lower than those required for (R)-2 and (S)-3, and that
(R)-9 and (R)-10, unlike (R)-2 and (S)-3, produce sodium channel frequency (use)-dependence
at low micromolar concentrations. We further show that (R)-7–(R)-10 displayed
excellent anticonvulsant activities and pain-attenuating properties
in the animal formalin model. Of these compounds, only (R)-7 reversed mechanical hypersensitivity in the tibial-nerve
injury model for neuropathic pain in rats.
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Affiliation(s)
| | - Xiao-Fang Yang
- Department
of Pharmacology and Neuroscience Graduate Interdisciplinary Program,
College of Medicine, University of Arizona, Tucson, Arizona 85742, United States
| | | | - Yuying Wang
- Department
of Pharmacology and Neuroscience Graduate Interdisciplinary Program,
College of Medicine, University of Arizona, Tucson, Arizona 85742, United States
| | | | | | - Rajesh Khanna
- Department
of Pharmacology and Neuroscience Graduate Interdisciplinary Program,
College of Medicine, University of Arizona, Tucson, Arizona 85742, United States
| | - Harold Kohn
- NeuroGate Therapeutics, Inc., 150
Fayetteville Street, Suite 2300, Raleigh, North Carolina 27601, United States
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Brittain JM, Wang Y, Wilson SM, Khanna R. Regulation of CREB signaling through L-type Ca2+channels by Nipsnap-2. Channels (Austin) 2014; 6:94-102. [DOI: 10.4161/chan.19415] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Chesta ME, Carbajal A, Arce CA, Bisig CG. Serum-induced neurite retraction in CAD cells--involvement of an ATP-actin retractile system and the lack of microtubule-associated proteins. FEBS J 2014; 281:4767-78. [PMID: 25112570 DOI: 10.1111/febs.12967] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 06/23/2014] [Accepted: 08/08/2014] [Indexed: 11/28/2022]
Abstract
Cultured catecholamine-differentiated cells [which lack the microtubule-associated proteins (MAPs): MAP1B, MAP2, Tau, STOP, and Doublecortin] proliferate in the presence of fetal bovine serum, and, in its absence, cease dividing and generate processes similar to the neurites of normal neurons. The reintroduction of serum induces neurite retraction, and proliferation resumes. The neurite retraction process in catecholamine-differentiated cells was partially characterized in this study. Microtubules in the cells were found to be in a highly dynamic state, and tubulin in the microtubules consisted primarily of the tyrosinated and deacetylated isotypes. Increased levels of acetylated or Δ2-tubulin (which are normally absent) did not prevent serum-induced neurite retraction. Treatment of differentiated cells with lysophosphatidic acid or adenosine deaminase induced neurite retraction. Inhibition of Rho-associated protein kinase, ATP depletion and microfilament disruption each (individually) blocked serum-induced neurite retraction, suggesting that an ATP-dependent actomyosin system underlies the mechanism of neurite retraction. Nocodazole treatment induced neurite retraction, but this effect was blocked by pretreatment with the microtubule-stabilizing drug paclitaxel (Taxol). Paclitaxel did not prevent serum-induced or lysophosphatidic acid-induced retraction, suggesting that integrity of microtubules (despite their dynamic state) is necessary to maintain neurite elongation, and that paclitaxel-induced stabilization alone is not sufficient to resist the retraction force induced by serum. Transfection with green fluorescent protein-Tau conferred resistance to retraction caused by serum. We hypothesize that, in normal neurons (cultured or in vivo), MAPs are necessary not only to stabilize microtubules, but also to establish interactions with other cytoskeletal or membrane components to form a stable structure capable of resisting the retraction force.
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Affiliation(s)
- María E Chesta
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), UNC-CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina
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7
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Lee H, Park KD, Torregrosa R, Yang XF, Dustrude ET, Wang Y, Wilson SM, Barbosa C, Xiao Y, Cummins TR, Khanna R, Kohn H. Substituted N-(biphenyl-4'-yl)methyl (R)-2-acetamido-3-methoxypropionamides: potent anticonvulsants that affect frequency (use) dependence and slow inactivation of sodium channels. J Med Chem 2014; 57:6165-82. [PMID: 25004277 PMCID: PMC4111400 DOI: 10.1021/jm500707r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
We
prepared 13 derivatives of N-(biphenyl-4′-yl)methyl
(R)-2-acetamido-3-methoxypropionamide that differed
in type and placement of a R-substituent in the terminal aryl unit.
We demonstrated that the R-substituent impacted the compound’s
whole animal and cellular pharmacological activities. In rodents,
select compounds exhibited excellent anticonvulsant activities and
protective indices (PI = TD50/ED50) that compared
favorably with clinical antiseizure drugs. Compounds with a polar,
aprotic R-substituent potently promoted Na+ channel slow
inactivation and displayed frequency (use) inhibition of Na+ currents at low micromolar concentrations. The possible advantage
of affecting these two pathways to decrease neurological hyperexcitability
is discussed.
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Affiliation(s)
- Hyosung Lee
- Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, and ‡Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599, United States
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8
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Wang Y, Wilson SM, Brittain JM, Ripsch MS, Salomé C, Park KD, White FA, Khanna R, Kohn H. Merging Structural Motifs of Functionalized Amino Acids and α-Aminoamides Results in Novel Anticonvulsant Compounds with Significant Effects on Slow and Fast Inactivation of Voltage-gated Sodium Channels and in the Treatment of Neuropathic Pain. ACS Chem Neurosci 2011; 2:317-322. [PMID: 21765969 DOI: 10.1021/cn200024z] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
We recently reported that merging key structural pharmacophores of the anticonvulsant drugs lacosamide (a functionalized amino acid) with safinamide (an α-aminoamide) resulted in novel compounds with anticonvulsant activities superior to that of either drug alone. Here, we examined the effects of six such chimeric compounds on Na(+)-channel function in central nervous system catecholaminergic (CAD) cells. Using whole-cell patch clamp electrophysiology, we demonstrated that these compounds affected Na(+) channel fast and slow inactivation processes. Detailed electrophysiological characterization of two of these chimeric compounds that contained either an oxymethylene ((R)-7) or a chemical bond ((R)-11) between the two aromatic rings showed comparable effects on slow inactivation, use-dependence of block, development of slow inactivation, and recovery of Na(+) channels from inactivation. Both compounds were equally effective at inducing slow inactivation; (R)-7 shifted the fast inactivation curve in the hyperpolarizing direction greater than (R)-11, suggesting that in the presence of (R)-7, a larger fraction of the channels are in an inactivated state. None of the chimeric compounds affected veratridine- or KCl-induced glutamate release in neonatal cortical neurons. There was modest inhibition of KCl-induced calcium influx in cortical neurons. Finally, a single intraperitoneal administration of (R)-7, but not (R)-11, completely reversed mechanical hypersensitivity in a tibial-nerve injury model of neuropathic pain. The strong effects of (R)-7 on slow and fast inactivation of Na(+) channels may contribute to its efficacy and provide a promising novel therapy for neuropathic pain, in addition to its antiepileptic potential.
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Affiliation(s)
- Yuying Wang
- Department Pharmacology and Toxicology, ‡Department of Anesthesia, and §Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- Department of Chemistry and ⊥Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Sarah M. Wilson
- Department Pharmacology and Toxicology, ‡Department of Anesthesia, and §Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- Department of Chemistry and ⊥Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Joel M. Brittain
- Department Pharmacology and Toxicology, ‡Department of Anesthesia, and §Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- Department of Chemistry and ⊥Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Matthew S. Ripsch
- Department Pharmacology and Toxicology, ‡Department of Anesthesia, and §Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- Department of Chemistry and ⊥Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Christophe Salomé
- Department Pharmacology and Toxicology, ‡Department of Anesthesia, and §Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- Department of Chemistry and ⊥Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Ki Duk Park
- Department Pharmacology and Toxicology, ‡Department of Anesthesia, and §Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- Department of Chemistry and ⊥Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Fletcher A. White
- Department Pharmacology and Toxicology, ‡Department of Anesthesia, and §Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- Department of Chemistry and ⊥Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Rajesh Khanna
- Department Pharmacology and Toxicology, ‡Department of Anesthesia, and §Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- Department of Chemistry and ⊥Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Harold Kohn
- Department Pharmacology and Toxicology, ‡Department of Anesthesia, and §Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, United States
- Department of Chemistry and ⊥Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599, United States
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Wang Y, Khanna R. VOLTAGE-GATED CALCIUM CHANNELS ARE NOT AFFECTED BY THE NOVEL ANTI-EPILEPTIC DRUG LACOSAMIDE. Transl Neurosci 2011; 2:13-22. [PMID: 21949591 PMCID: PMC3178266 DOI: 10.2478/s13380-011-0002-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The novel anti-epileptic drug lacosamide targets two proteins - voltage-gated sodium channels and collapsin response mediator protein 2 (CRMP-2) - suggesting dual modes of action for lacosamide. We recently identified the neurite outgrowth and axonal guidance protein CRMP-2 as a novel partner and regulator of the presynaptic N-type voltage-gated Ca(2+) channel (CaV2.2) [Brittain et al., J. Biol. Chem. 284: 31375-31390 (2009)]. Here we examined the effects of lacosamide on voltage-gated Ba(2+) channels. Lacosamide did not affect Ba(2+) currents via N- and P/Q- channels in rat hippocampal neurons or L-type Ca(2+) channels in a mouse CNS neuronal cell line, respectively. N-type Ba(2+) currents, augmented by CRMP-2 expression, were also unaffected by acute or chronic lacosamide exposure. These results establish that the anti-epileptic mode of action of lacosamide does not involve these voltage-gated Ca(2+) channels.
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Affiliation(s)
- Yuying Wang
- Department of Pharmacology and Toxicology, Indiana University, School of Medicine, Indianapolis, IN 46202, USA
- Paul and Carole Stark Neurosciences, Research Institute, Indiana University, School of Medicine, Indianapolis, IN 46202, USA
| | - Rajesh Khanna
- Department of Pharmacology and Toxicology, Indiana University, School of Medicine, Indianapolis, IN 46202, USA
- Paul and Carole Stark Neurosciences, Research Institute, Indiana University, School of Medicine, Indianapolis, IN 46202, USA
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10
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Wang Y, Park KD, Salomé C, Wilson SM, Stables JP, Liu R, Khanna R, Kohn H. Development and characterization of novel derivatives of the antiepileptic drug lacosamide that exhibit far greater enhancement in slow inactivation of voltage-gated sodium channels. ACS Chem Neurosci 2011; 2:90-106. [PMID: 21532923 DOI: 10.1021/cn100089b] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The novel antiepileptic drug, (R)-N-benzyl 2-acetamido-3-methoxypropionamide ((R)-lacosamide, Vimpat(®) ((R)-1)), was recently approved in the US and Europe for adjuvant treatment of partial-onset seizures in adults. (R)-1 preferentially enhances slow inactivation of voltage-gated Na(+) currents, a pharmacological process relevant in the hyperexcitable neuron. We have advanced a strategy to identify lacosamide binding partners by attaching affinity bait (AB) and chemical reporter (CR) groups to (R)-1 to aid receptor detection and isolation. We showed that select lacosamide AB and AB&CR derivatives exhibited excellent activities similar to (R)-1 in the maximal electroshock seizure model in rodents. Here, we examined the effect of these lacosamide AB and AB&CR derivatives and compared them with (R)-1 on Na(+) channel function in CNS catecholaminergic (CAD) cells. Using whole-cell patch clamp electrophysiology, we demonstrated that the test compounds do not affect the Na(+) channel fast inactivation process, that they were far better modulators of slow inactivation than (R)-1, and that modulation of the slow inactivation process was stereospecific. The lacosamide AB agents that contained either an electrophilic isothiocyanate ((R)-5) or a photolabile azide ((R)-8) unit upon AB activation gave modest levels of permanent Na(+) channel slow inactivation, providing initial evidence that these compounds may have covalently reacted with their cognate receptor(s). Our findings support the further use of these agents to delineate the (R)-1-mediated Na(+) channel slow inactivation process.
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Affiliation(s)
| | - Ki Duk Park
- Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy
| | - Christophe Salomé
- Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy
| | | | - James P. Stables
- Epilepsy Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 6001 Executive Boulevard, Suite 2106, Rockville, Maryland 20892, United States
| | - Rihe Liu
- Carolina Center for Genome Sciences
- Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy
| | - Rajesh Khanna
- Departments of Pharmacology and Toxicology
- Program in Medical Neuroscience
| | - Harold Kohn
- Department of Chemistry
- Division of Medicinal Chemistry and Natural Products, UNC Eshelman School of Pharmacy
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11
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Wang Y, Brittain JM, Jarecki BW, Park KD, Wilson SM, Wang B, Hale R, Meroueh SO, Cummins TR, Khanna R. In silico docking and electrophysiological characterization of lacosamide binding sites on collapsin response mediator protein-2 identifies a pocket important in modulating sodium channel slow inactivation. J Biol Chem 2010; 285:25296-307. [PMID: 20538611 DOI: 10.1074/jbc.m110.128801] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The anti-epileptic drug (R)-lacosamide ((2R)-2-(acetylamino)-N-benzyl-3-methoxypropanamide (LCM)) modulates voltage-gated sodium channels (VGSCs) by preferentially interacting with slow inactivated sodium channels, but the observation that LCM binds to collapsin response mediator protein 2 (CRMP-2) suggests additional mechanisms of action for LCM. We postulated that CRMP-2 levels affects the actions of LCM on VGSCs. CRMP-2 labeling by LCM analogs was competitively displaced by excess LCM in rat brain lysates. Manipulation of CRMP-2 levels in the neuronal model system CAD cells affected slow inactivation of VGSCs without any effects on other voltage-dependent properties. In silico docking was performed to identify putative binding sites in CRMP-2 that may modulate the effects of LCM on VGSCs. These studies identified five cavities in CRMP-2 that can accommodate LCM. CRMP-2 alanine mutants of key residues within these cavities were functionally similar to wild-type CRMP-2 as assessed by similar levels of enhancement in dendritic complexity of cortical neurons. Next, we examined the effects of expression of wild-type and mutant CRMP-2 constructs on voltage-sensitive properties of VGSCs in CAD cells: 1) steady-state voltage-dependent activation and fast-inactivation properties were not affected by LCM, 2) CRMP-2 single alanine mutants reduced the LCM-mediated effects on the ability of endogenous Na(+) channels to transition to a slow inactivated state, and 3) a quintuplicate CRMP-2 alanine mutant further decreased this slow inactivated fraction. Collectively, these results identify key CRMP-2 residues that can coordinate LCM binding thus making it more effective on its primary clinical target.
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Affiliation(s)
- Yuying Wang
- Department of Pharmacology and Toxicology, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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12
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Harvey VL, Saul MW, Garner C, McDonald RL. A role for the volume regulated anion channel in volume regulation in the murine CNS cell line, CAD. Acta Physiol (Oxf) 2010; 198:159-68. [PMID: 19811460 DOI: 10.1111/j.1748-1716.2009.02050.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM The role of the volume regulated anion channel (VRAC) in a model CNS neuronal cell line, CAD, was investigated. METHODS Changes in cell volume following hypotonic challenges were measured using a video-imaging technique. The effect of the Cl(-) channel antagonists tamoxifen (10 microm) and 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS; 100 microm) on regulatory volume decrease (RVD) were measured. The whole-cell voltage-clamp technique was used to characterize ICl(swell), the current underlying the VRAC. RESULTS Using the video-imaging technique, CAD cells were found to swell and subsequently exhibit RVD when subjected to a sustained hypotonic challenge from 300 mOsmol kg(-1) H(2)O to 210 mOsmol kg(-1) H(2)O. In the presence of tamoxifen (10 microm) or DIDS (100 microm) RVD was abolished, suggesting a role for the VRAC. A hypotonic solution (230 mOsmol kg(-1) H(2)O) evoked ICl(swell), an outwardly rectifying current displaying time-independent activation, which reversed upon return to isotonic conditions. The reversal potential (E(rev)) for ICl(swell) was -14.7 + or - 1.4 mV, similar to the theoretical E(rev) for a selective Cl(-) conductance. ICl(swell) was inhibited in the presence of DIDS (100 microm) and tamoxifen (10 microm), the DIDS inhibition being voltage dependent. CONCLUSIONS Osmotic swelling elicits an outwardly rectifying Cl(-) conductance in CAD cells. The ICl(swell) observed in these cells is similar to that observed in other cells, and is likely to provide a pathway for the loss of Cl(-) which leads to water loss and RVD. As ischaemia, brain trauma, hypoxia and other brain pathologies can cause cell swelling, CAD cells represent a model cell line for the study of neuronal cell volume regulation.
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Affiliation(s)
- V L Harvey
- Neuroscience, Pharmacology & Physiology, University College London, Gower Street, London WC1E 6BT, UK.
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13
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Bisig CG, Chesta ME, Zampar GG, Purro SA, Santander VS, Arce CA. Lack of stabilized microtubules as a result of the absence of major maps in CAD cells does not preclude neurite formation. FEBS J 2009; 276:7110-23. [DOI: 10.1111/j.1742-4658.2009.07422.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Dron M, Dandoy-Dron F, Farooq Salamat MK, Laude H. Proteasome inhibitors promote the sequestration of PrPSc into aggresomes within the cytosol of prion-infected CAD neuronal cells. J Gen Virol 2009; 90:2050-2060. [PMID: 19339478 DOI: 10.1099/vir.0.010082-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dysfunction of the endoplasmic reticulum associated protein degradation/proteasome system is believed to contribute to the initiation or aggravation of neurodegenerative disorders associated with protein misfolding, and there is some evidence to suggest that proteasome dysfunctions might be implicated in prion disease. This study investigated the effect of proteasome inhibitors on the biogenesis of both the cellular (PrP(C)) and abnormal (PrP(Sc)) forms of prion protein in CAD neuronal cells, a newly introduced prion cell system. In uninfected cells, proteasome impairment altered the intracellular distribution of PrP(C), leading to a strong accumulation in the Golgi apparatus. Moreover, a detergent-insoluble and weakly protease-resistant PrP species of 26 kDa, termed PrP(26K), accumulated in the cells, whether they were prion-infected or not. However, no evidence was found that, in infected cells, this PrP(26K) species converts into the highly proteinase K-resistant PrP(Sc). In the infected cultures, proteasome inhibition caused an increased intracellular aggregation of PrP(Sc) that was deposited into large aggresomes. These findings strengthen the view that, in neuronal cells expressing wild-type PrP(C) from the natural promoter, proteasomal impairment may affect both the process of PrP(C) biosynthesis and the subcellular sites of PrP(Sc) accumulation, despite the fact that these two effects could essentially be disconnected.
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Affiliation(s)
- Michel Dron
- INRA, U892 Virologie Immunologie Moléculaires, F-78350 Jouy-en-Josas, France
| | - Françoise Dandoy-Dron
- Centre National de la Recherche Scientifique, FRE2942, Oncologie Virale, F-94801 Villejuif, France
| | | | - Hubert Laude
- INRA, U892 Virologie Immunologie Moléculaires, F-78350 Jouy-en-Josas, France
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15
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McFarland MJ, Bardell TK, Yates ML, Placzek EA, Barker EL. RNA Interference-Mediated Knockdown of Dynamin 2 Reduces Endocannabinoid Uptake into Neuronal dCAD Cells. Mol Pharmacol 2008; 74:101-8. [DOI: 10.1124/mol.108.044834] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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16
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Li Y, Hou LXE, Aktiv A, Dahlström A. Studies of the central nervous system-derived CAD cell line, a suitable model for intraneuronal transport studies? J Neurosci Res 2008; 85:2601-9. [PMID: 17335077 DOI: 10.1002/jnr.21216] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The CAD cell line is a variant of a CNS-derived Cath.a cell line established by targeted oncogenesis in transgenic mice. Cell differentiation of the cell line can be induced by "starvation," i.e., removal of serum from the culture medium (protein-free medium). The differentiated CAD cells extend long processes, which ultrastructurally contain abundant microtubules, intermediate filaments, and various synaptic vesicles/organelles in the varicose enlargements, thus resembling neurites. Histochemical studies demonstrated that the differentiated cells express a number of synaptic vesicle proteins, cytoskeletons, different neurotransmitter enzymes, neuropeptides, and glia proteins. The data suggest that the differentiated CAD cells may be a suitable model for studies of intraneuronal transport, recycling of receptors, and pharmacological investigations.
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Affiliation(s)
- Yongling Li
- Department of Medical Chemistry and Cell Biology, Institute of Biomedicine, Göteborg University, Göteborg, Sweden.
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17
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Arboleda G, Huang TJ, Waters C, Verkhratsky A, Fernyhough P, Gibson RM. Insulin-like growth factor-1-dependent maintenance of neuronal metabolism through the phosphatidylinositol 3-kinase-Akt pathway is inhibited by C2-ceramide in CAD cells. Eur J Neurosci 2007; 25:3030-8. [PMID: 17561816 DOI: 10.1111/j.1460-9568.2007.05557.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Ceramide is a lipid second-messenger generated in response to stimuli associated with neurodegeneration that induces apoptosis, a mechanism underlying neuronal death in Parkinson's disease. We tested the hypothesis that insulin-like growth factor-1 (IGF-1) could mediate a metabolic response in CAD cells, a dopaminergic cell line of mesencephalic origin that differentiate into a neuronal-like phenotype upon serum removal, extend processes resembling neurites, synthesize abundant dopamine and noradrenaline and express the catecholaminergic biosynthetic enzymes tyrosine hydroxylase and dopamine beta-hydroxylase, and that this process was phosphatidylinositol 3-kinase (PI 3-K)-Akt-dependent and could be inhibited by C(2)-ceramide. The metabolic response was evaluated as real-time changes in extracellular acidification rate (ECAR) using microphysiometry. The IGF-1-induced ECAR response was associated with increased glycolysis, determined by increased NAD(P)H reduction, elevated hexokinase activity and Akt phosphorylation. C(2)-ceramide inhibited all these changes in a dose-dependent manner, and was specific, as it was not induced by the inactive C(2)-ceramide analogue C(2)-dihydroceramide. Inhibition of the upstream kinase, PI 3-K, also inhibited Akt phosphorylation and the metabolic response to IGF-1, similar to C(2)-ceramide. Decreased mitochondrial membrane potential occurred after loss of Akt phosphorylation. These results show that IGF-1 can rapidly modulate neuronal metabolism through PI 3-K-Akt and that early metabolic inhibition induced by C(2)-ceramide involves blockade of the PI 3-K-Akt pathway, and may compromise the first step of glycolysis. This may represent a new early event in the C(2)-ceramide-induced cell death pathway that could coordinate subsequent changes in mitochondria and commitment of neurons to apoptosis.
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Affiliation(s)
- Gonzalo Arboleda
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK.
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18
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Sousa AD, Berg JS, Robertson BW, Meeker RB, Cheney RE. Myo10 in brain: developmental regulation, identification of a headless isoform and dynamics in neurons. J Cell Sci 2006; 119:184-94. [PMID: 16371656 DOI: 10.1242/jcs.02726] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Although Myo10 (myosin-X) is an unconventional myosin associated with filopodia, little is known about its isoforms and roles in the nervous system. We report here that, in addition to full-length Myo10, brain expresses a shorter form of Myo10 that lacks a myosin head domain. This ;headless' Myo10 is thus unable to function as a molecular motor, but is otherwise identical to full-length Myo10 and, like it, contains three pleckstrin homology (PH) domains, a myosin-tail homology 4 (MyTH4) domain, and a band-4.1/ezrin/radixin/moesin (FERM) domain. Immunoblotting demonstrates that both full-length and headless Myo10 exhibit dramatic developmental regulation in mouse brain. Immunofluorescence with an antibody that detects both isoforms demonstrates that Myo10 is expressed in neurons, such as Purkinje cells, as well as non-neuronal cells, such as astrocytes and ependymal cells. CAD cells, a neuronal cell line, express both full-length and headless Myo10, and this endogenous Myo10 is present in cell bodies, neurites, growth cones and the tips of filopodia. To investigate the dynamics of the two forms of Myo10 in neurons, CAD cells were transfected with GFP constructs corresponding to full-length or headless Myo10. Only full-length Myo10 localizes to filopodial tips and undergoes intrafilopodial motility, demonstrating that the motor domain is necessary for these activities. Live cell imaging also reveals that full-length Myo10 localizes to the tips of neuronal filopodia as they explore and interact with their surroundings, suggesting that this myosin has a role in neuronal actin dynamics.
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Affiliation(s)
- Aurea D Sousa
- Department of Cell and Molecular Physiology, Medical Biomolecular Research Building (MBRB), University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7545, USA
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19
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Abstract
CAD (Cath.a-differentiated) cells, a mouse neuronal cell line, were subjected to electrohydrodynamic jetting at a field strength of 0.47-0.67 kV/mm, corresponding to an applied voltage of 7-10 kV. After jetting, the cells appeared normal and continued to divide at rates similar to those shown by control samples. Jetted cells, when placed in serum-free medium, underwent differentiation that was sustained for at least 1 month. Some of the droplets produced by jetting contained only a few cells. These results indicate that the process of jetting does not significantly perturb neuronal cells and that this novel approach might in the future be a useful way to deposit small numbers of living nerve cells on to surfaces.
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Affiliation(s)
- Peter A M Eagles
- Kings College London, University of London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, St. Thomas Street, London SE1 1UL, UK.
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20
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Li Y, Hou LXE, Aktiv A, Dahlström A. Immunohistochemical characterisation of differentiated CAD cells: expression of peptides and chromogranins. Histochem Cell Biol 2005; 124:25-33. [PMID: 16007468 DOI: 10.1007/s00418-005-0017-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2005] [Indexed: 10/25/2022]
Abstract
The CNS-derived cell line, CAD cell line, when grown in a protein free medium (PFM), differentiates to neuron-like cells with very long processes. It was previously studied biochemically and found to express TH activity, some neurospecific proteins, but no glial proteins. We have now further studied the CAD cells and focused on the expression of various neuropeptides, GAP-43 and GFAP. All peptides studied were present, including TH, but also GFAP, in contrast to earlier studies. A different kind of processes, short, slender and distributed like a "fringe" around cell body and along processes was observed, NESP55 but not other chromogranins was present in these "fringes", GAP43 showed some degree of overlapping with NESP55. The results show that even after differentiation in PFM, the CAD cells express a palette of neuropeptides and chromogranins, catecholaminergic markers as well as the glia-specific GFAP. Our efforts to induce exocytosis/endocytosis from the peptide granules by high K+ were, however, unsuccessful. Due to long processes, the CAD cells may represent a good model for studying intracellular transport, and, since the cells express both neuronal and glial characteristics, it may be useful for investigating the influence of different trophic/growth factors on the expression of various neuronal characteristics.
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Affiliation(s)
- Yongling Li
- Department of Anatomy and Cell Biology, Medical Faculty, Göteborg University, 420, 405 30, Göteborg, Sweden.
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21
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Colton CA, Xu Q, Burke JR, Bae SY, Wakefield JK, Nair A, Strittmatter WJ, Vitek MP. Disrupted spermine homeostasis: a novel mechanism in polyglutamine-mediated aggregation and cell death. J Neurosci 2005; 24:7118-27. [PMID: 15306645 PMCID: PMC6729181 DOI: 10.1523/jneurosci.1233-04.2004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Our data suggest a novel mechanism whereby pathological-length polyglutamine (polyQ) proteins promote the spermine synthetic pathway, increasing polyQ-aggregation and cell death. As detected in a cell-free turbidity assay, spermine promotes aggregation of thio-polyQ62 in a dose-dependent manner. Using a stable neuronal cell line expressing pathological-length [polyQ57-yellow fluorescent protein (YFP) (Q57)] or non-pathological-length [polyQ19-YFP (Q19)] polyglutamine protein, we show that multiple steps in the production of polyamines are affected in Q57 cells, suggesting dysfunctional spermine homeostasis. As the building block for spermine synthesis, arginine transport is significantly increased in neuronal cell lines stably expressing Q57. Q57 lines displayed upregulated basal and inducible arginase I activities that were not seen in polyQ19-YFP lines. Normal induction of spermidine/spermine N-acetyltransferase in Q19 lines regulating back-conversion of spermine, thereby reducing spermine levels, however, was not observed in Q57 lines. Pharmacological activation of ornithine decarboxylase (ODC), a key enzyme of the polyamine synthetic pathway, increased cellular aggregates and increased cell death in Q57 cells not observed in Q19 cells. Inhibition of ODC by difluoromethylornithine prevented basal and induced cell death in Q57 cells, demonstrating a central role for polyamines in this process.
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Affiliation(s)
- C A Colton
- Deane Laboratory, Division of Neurology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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22
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Xu Q, Wink DA, Colton CA. Nitric oxide production and regulation of neuronal NOS in tyrosine hydroxylase containing neurons. Exp Neurol 2004; 188:341-50. [PMID: 15246834 DOI: 10.1016/j.expneurol.2004.04.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2003] [Revised: 04/14/2004] [Accepted: 04/21/2004] [Indexed: 10/26/2022]
Abstract
CAD cells are a murine CNS catecholaminergic (tyrosine hydroxylase-positive; TH+) neuronal cell line that undergoes morphological differentiation to resemble CNS catecholaminergic neurons upon serum deprivation. We show here that CAD cells also express neuronal nitric oxide synthase (nNOS) mRNA and protein and produce readily measurable levels of NO. Since both NO and catecholamines (L-DOPA; dopamine; norepinephrine) are redox active molecules, their production within the same cell may affect the cell's vulnerability to insult. Thus, we examined the regulation of NO production by CAD cells and the effect of NO on cell survival. NO is generated in a dose-dependent fashion by treatment with agents (ionomycin; A23817; KCl) known to increase calcium entry across the cell membrane. The NO level can be increased further by pretreatment with sepiapterin, a membrane permeable precursor for BH4 synthesis, suggesting that the BH4 levels or access required for nNOS activation is limited in CAD cells. Reducing mitochondrial Ca2+ uptake using ruthenium red (RuR) increased ionomycin-mediated NO production over ionomycin alone and indicates a critical role for mitochondria in nNOS regulation. Cell death was significantly increased by ionomycin treatment alone or in conjunction with reduced mitochondrial Ca2+ uptake. However, NO was not the primary mediator of cell death since NOS inhibitors rescued only less than 10% of the cells. These data suggest that endogenous NO production by nNOS is not a major factor in CAD cell death under these conditions.
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Affiliation(s)
- Qing Xu
- Division of Neurology, Duke University Medical Center, Durham, NC 27710, USA
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23
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Pasuit JB, Li Z, Kuzhikandathil EV. Multi-modal regulation of endogenous D1 dopamine receptor expression and function in the CAD catecholaminergic cell line. J Neurochem 2004; 89:1508-19. [PMID: 15189354 DOI: 10.1111/j.1471-4159.2004.02450.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dopamine receptors exhibit tissue- and cell type-specific expression that is modulated during development, aging and in diseases such as Parkinson's. The molecular mechanisms regulating expression of dopamine receptors are not well understood, in part due to the lack of a model cell line that not only expresses endogenous dopamine receptors but also has the requisite regulatory mechanisms. Here, we demonstrate that the CAD catecholaminergic cell line expresses D1, D2, D3 and D5 dopamine receptor subtypes and associated signaling proteins. CAD cell differentiation induced by serum withdrawal increases the levels of D1 receptor mRNA by transcriptional up-regulation. This increase is also mimicked by the neurotrophin NT3. Interestingly, the increase of D1 receptor mRNA does not result in increased levels of D1 receptor protein in differentiated CAD cells. Furthermore, while the D1 receptor protein is expressed in differentiated CAD cells, it loses its ability to activate adenylyl cyclase. We demonstrate that the post-transcriptional regulation is not due to decreased D1 receptor mRNA stability or generation of a truncated D1 receptor mRNA, and that the down-regulation of D1 receptor function in differentiated CAD cells is mediated by post-translational mechanisms that decrease cell surface receptor expression by altering receptor processing and trafficking.
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Affiliation(s)
- Jennifer B Pasuit
- Department of Pharmacology and Physiology, UMDNJ-New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103, USA
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24
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Dandoy-Dron F, Griffond B, Mishal Z, Tovey MG, Dron M. Scrg1, a novel protein of the CNS is targeted to the large dense-core vesicles in neuronal cells. Eur J Neurosci 2003; 18:2449-59. [PMID: 14622145 DOI: 10.1046/j.1460-9568.2003.03009.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Scrapie responsive gene one (Scrg1) is a novel transcript discovered through identification of the genes associated with or responsible for the neurodegenerative changes observed in transmissible spongiform encephalopathies. Scrg1 mRNA is distributed principally in the central nervous system and the cDNA sequence predicts a small cysteine-rich protein 98 amino acids in length, with a N-terminal signal peptide. In this study, we have generated antibodies against the predicted protein and revealed expression of a predominant immunoreactive protein of 10 kDa in mouse brain by Western blot analysis. We have established CAD neuronal cell lines stably expressing Scrg1 to determine its subcellular localization. Several lines of evidence show that the protein is targeted to dense-core vesicles in these cells. (i) Scrg1 is detected by immunocytochemistry as very punctate signals especially in the Golgi apparatus and tips of neurites, suggesting a vesicular localization for the protein. Moreover, Scrg1 exhibits a high degree of colocalization with secretogranin II, a dense-core vesicle marker and a very limited colocalization with markers for small synaptic vesicles. (ii) Scrg1 immunoreactivity is associated with large secretory granules/dense-core vesicles, as indicated by immuno-electron microscopy. (iii) Scrg1 is enriched in fractions of sucrose density gradient where synaptotagmin V, a dense-core vesicle-associated protein, is also enriched. The characteristic punctate immunostaining of Scrg1 is observed in N2A cells transfected with Scrg1 and for the endogenous protein in cultured primary neurons, attesting to the generality of the observations. Our findings strongly suggest that Scrg1 is associated with the secretory pathway of neuronal cells.
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Affiliation(s)
- Françoise Dandoy-Dron
- Laboratoire d'Oncologie Virale, CNRS UPR 9045, 7 rue G. Môquet BP-8, 94801 Villejuif Cedex, France
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