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Abstract
Global and focal ischemias induce a variety of gene families, including immediate early genes, cytokines, neurotransmitter receptors, and heat-shock proteins. The Janus-like effects of several of these gene prod ucts promote neuronal survival and degeneration. Therefore, determining the molecular pathways respon sible for the differential regulation of these genes is of paramount importance. The discovery of apoptosis as a mediator of delayed neuronal death has led to the identification of a number of other genes involved in postischemic brain damage. Future neuroprotective therapies for cerebral ischemia may be directed at preventing alterations in gene expression. NEUROSCIENTIST 5:238-253, 1999
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Affiliation(s)
- Sean I. Savitz
- Department of Neurology, Neuroscience, Albert Einstein
College of Medicine Bronx, New York
| | - Daniel M. Rosenbaum
- Department of Neurology, Neuroscience and Ophthalmology
Albert Einstein College of Medicine Bronx, New York
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2
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Pourbadie HG, Naderi N, Mehranfard N, Janahmadi M, Khodagholi F, Motamedi F. Preventing effect of L-type calcium channel blockade on electrophysiological alterations in dentate gyrus granule cells induced by entorhinal amyloid pathology. PLoS One 2015; 10:e0117555. [PMID: 25689857 PMCID: PMC4331091 DOI: 10.1371/journal.pone.0117555] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 12/26/2014] [Indexed: 12/12/2022] Open
Abstract
The entorhinal cortex (EC) is one of the earliest affected brain regions in Alzheimer's disease (AD). EC-amyloid pathology induces synaptic failure in the dentate gyrus (DG) with resultant behavioral impairment, but there is little known about its impact on neuronal properties in the DG. It is believed that calcium dyshomeostasis plays a pivotal role in the etiology of AD. Here, the effect of the EC amyloid pathogenesis on cellular properties of DG granule cells and also possible neuroprotective role of L-type calcium channel blockers (CCBs), nimodipine and isradipine, were investigated. The amyloid beta (Aβ) 1-42 was injected bilaterally into the EC of male rats and one week later, electrophysiological properties of DG granule cells were assessed. Voltage clamp recording revealed appearance of giant sIPSC in combination with a decrease in sEPSC frequency which was partially reversed by CCBs in granule cells from Aβ treated rats. EC amyloid pathogenesis induced a significant reduction of input resistance (Rin) accompanied by a profound decreased excitability in the DG granule cells. However, daily administration of CCBs, isradipine or nimodipine (i.c.v. for 6 days), almost preserved the normal excitability against Aβ. In conclusion, lower tendency to fire AP along with reduced Rin suggest that DG granule cells might undergo an alteration in the membrane ion channel activities which finally lead to the behavioral deficits observed in animal models and patients with early-stage Alzheimer's disease.
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Affiliation(s)
- Hamid Gholami Pourbadie
- Department of Physiology and Pharmacology, Pasteur Institute of Iran, Tehran, Iran
- Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Nima Naderi
- Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Department of Pharmacology and Toxicology, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Nasrin Mehranfard
- Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mahyar Janahmadi
- Neurophysiology Research Center, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Fariba Khodagholi
- Neurobiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Fereshteh Motamedi
- Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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3
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Kurokawa K, Mizuno K, Ohkuma S. Increase of ryanodine receptors by dopamine D1 receptors is negatively regulated by γ-aminobutyric acid type B receptors in primary cultures of mouse cerebral cortical neurons. J Neurosci Res 2012; 90:1626-38. [PMID: 22504960 DOI: 10.1002/jnr.23058] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 02/23/2012] [Accepted: 03/04/2012] [Indexed: 11/06/2022]
Abstract
Although upregulation of ryanodine receptor (RyR)-1 and -2 is mediated through the activation of dopamine D1 receptors (D1DRs) in the development of psychostimulant-induced place preference, little is known about how such increased expressions of RyRs are negatively regulated. This study investigated negative regulatory mechanisms of increase of RyR-1 and -2 expression by D1DR stimulation with its full agonist, SKF82958 or A 68930, using cultures of mouse cerebral cortical neurons. Sustained exposure to SKF82958 or A 68930 of the neurons increased RyR-1 and -2 proteins in a dose- and time-dependent-manner. The SKF82958-induced increases of RyR-1 and -2 proteins were significantly suppressed by SCH23390 (a selective D1DR antagonist). In addition, the SKF82958- or A 68930-induced increases of RyR-1 and -2 proteins were completely abolished by baclofen (a selective γ-aminobutyric acid type B [GABA(B)] receptor agonist), whereas muscimol (an agonist specific to GABA(A) receptors) had no effect. SKF82958 or A 68930 significantly increased intracellular cAMP level, which was completely suppressed by baclofen. Furthermore, sustained exposure to phorbol 12,13-dibutyrate, a protein kinase C activator, did not change the expression of RyR-1 or -2 proteins. Immunohistochemical study showed colocalizaton of immunoreactivities for three types of proteins, D1DRs and GABA(B) receptor R1 and R2 subunits in the same neuronal bodies, suggesting that the neurochemical changes induced by the activation of D1DRs and GABA(B) receptors occur in the same neurons. These results indicate that RyR-1 and -2 expression facilitated by D1DR stimulation are negatively regulated by GABA(B) receptor via suppression of cAMP production.
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Affiliation(s)
- Kazuhiro Kurokawa
- Department of Pharmacology, Kawasaki Medical School, Kurashiki, Okayama, Japan
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4
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Kim S, Rhim H. Effects of amyloid-β peptides on voltage-gated L-type Ca(V)1.2 and Ca(V)1.3 Ca(2+) channels. Mol Cells 2011; 32:289-94. [PMID: 21822937 PMCID: PMC3887631 DOI: 10.1007/s10059-011-0075-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 05/18/2011] [Accepted: 06/24/2011] [Indexed: 01/01/2023] Open
Abstract
Overload of intracellular Ca(2+) has been implicated in the pathogenesis of neuronal disorders, such as Alzheimer's disease. Various mechanisms produce abnormalities in intracellular Ca(2+) homeostasis systems. L-type Ca(2+) channels have been known to be closely involved in the mechanisms underlying the neurodegenerative properties of amyloid-β (Aβ) peptides. However, most studies of L-type Ca(2+) channels in Aβ-related mechanisms have been limited to Ca(V)1.2, and surprisingly little is known about the involvement of Ca(V)1.3 in Aβ-induced neuronal toxicity. In the present study, we examined the expression patterns of Ca(V)1.3 after Aβ(25-35) exposure for 24 h and compared them with the expression patterns of Ca(V)1.2. The expression levels of Ca(V)1.3 were not significantly changed by Aβ(25-35) at both the mRNA levels and the total protein level in cultured hippocampal neurons. However, surface protein levels of Ca(V)1.3 were significantly increased by Aβ(25-35), but not by Aβ(35-25). We next found that acute treatment with Aβ(25-35) increased Ca(V)1.3 channel activities in HEK293 cells using whole-cell patch-clamp recordings. Furthermore, using GTP pulldown and co-immunoprecipitation assays in HEK293 cell lysates, we found that amyloid precursor protein interacts with β(3) subunits of Ca(2+) channels instead of Ca(V)1.2 or Ca(V)1.3 α(1) subunits. These results show that Aβ(25-35) chronically or acutely upregulates Ca(V)1.3 in the rat hippocampal and human kidney cells (HEK293). This suggests that Ca(V)1.3 has a potential role along with Ca(V)1.2 in the pathogenesis of Alzheimer's disease.
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Affiliation(s)
- Sunoh Kim
- Jeollanamdo Institute of Natural Resources Research, Jangheung 529-851, Korea
| | - Hyewhon Rhim
- Biomedical Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea
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5
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Karakikes I, Kim M, Hadri L, Sakata S, Sun Y, Zhang W, Chemaly ER, Hajjar RJ, Lebeche D. Gene remodeling in type 2 diabetic cardiomyopathy and its phenotypic rescue with SERCA2a. PLoS One 2009; 4:e6474. [PMID: 19649297 PMCID: PMC2714457 DOI: 10.1371/journal.pone.0006474] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Accepted: 07/03/2009] [Indexed: 12/31/2022] Open
Abstract
Background/Aim Diabetes-associated myocardial dysfunction results in altered gene expression in the heart. We aimed to investigate the changes in gene expression profiles accompanying diabetes-induced cardiomyopathy and its phenotypic rescue by restoration of SERCA2a expression. Methods/Results Using the Otsuka Long-Evans Tokushima Fatty rat model of type 2 diabetes and the Agilent rat microarray chip, we analyzed gene expression by comparing differential transcriptional changes in age-matched control versus diabetic hearts and diabetic hearts that received gene transfer of SERCA2a. Microarray expression profiles of selected genes were verified with real-time qPCR and immunoblotting. Our analysis indicates that diabetic cardiomyopathy is associated with a downregulation of transcripts. Diabetic cardiomyopathic hearts have reduced levels of SERCA2a. SERCA2a gene transfer in these hearts reduced diabetes-associated hypertrophy, and differentially modulated the expression of 76 genes and reversed the transcriptional profile induced by diabetes. In isolated cardiomyocytes in vitro, SERCA2a overexpression significantly modified the expression of a number of transcripts known to be involved in insulin signaling, glucose metabolism and cardiac remodeling. Conclusion This investigation provided insight into the pathophysiology of cardiac remodeling and the potential role of SERCA2a normalization in multiple pathways in diabetic cardiomyopathy.
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Affiliation(s)
- Ioannis Karakikes
- Cardiovascular Research Center, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Maengjo Kim
- Cardiovascular Research Center, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Lahouaria Hadri
- Cardiovascular Research Center, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Susumu Sakata
- Department of Physiology II, Nara Medical University, Kashihara, Nara, Japan
| | - Yezhou Sun
- Bioinformatics Laboratory of Personalized Medicine Research Program, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Weijia Zhang
- Bioinformatics Laboratory of Personalized Medicine Research Program, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Elie R. Chemaly
- Cardiovascular Research Center, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Roger J. Hajjar
- Cardiovascular Research Center, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Djamel Lebeche
- Cardiovascular Research Center, Mount Sinai School of Medicine, New York, New York, United States of America
- * E-mail:
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6
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Kim S, Yun HM, Baik JH, Chung KC, Nah SY, Rhim H. Functional interaction of neuronal Cav1.3 L-type calcium channel with ryanodine receptor type 2 in the rat hippocampus. J Biol Chem 2007; 282:32877-89. [PMID: 17823125 DOI: 10.1074/jbc.m701418200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuronal L-type Ca(2+) channels do not support synaptic transmission, but they play an essential role in synaptic activity-dependent gene expression. Ca(v)1.2 and Ca(v)1.3 are the two most widely expressed L-type Ca(2+) channels in neurons and have different biophysical and subcellular distributions. The function of the Ca(v) 1.3 L-type Ca(2+) channel and its cellular mechanisms in the central nervous system are poorly understood. In this study, using a yeast two-hybrid assay, we found that the N terminus of the rat Ca(v)1.3 alpha(1) subunit interacts with a partial N-terminal amino acid sequence of ryanodine receptor type 2 (RyR2). Reverse transcription-PCR and Western blot assays revealed high expression of both Ca(v)1.3 and RyR2 in the rat hippocampus. We also demonstrate a physical association of Ca(v)1.3 with RyR2 using co-immunoprecipitation assays. Moreover, immunocytochemistry revealed prominent co-localization between Ca(v)1.3 and RyR2 in hippocampal neurons. Depolarizing cells by an acute treatment of a high concentration of KCl (high-K, 60 mm) showed that the activation of L-type Ca(2+) channels induced RyR opening and led to RyR-dependent Ca(2+) release, even in the absence of extracellular Ca(2+). Furthermore, we found that RyR2 mRNA itself is increased by long term treatment of high-K via activation of L-type Ca(2+) channels. These acute and long term effects of high-K on RyRs were selectively blocked by small interfering RNA-mediated silencing of Ca(v)1.3. These results suggest a physical and functional interaction between Ca(v)1.3 and RyR2 and important implications of Ca(v)1.3/RyR2 clusters in translating synaptic activity into alterations in gene expression.
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Affiliation(s)
- Sunoh Kim
- Life Sciences Division, Korea Institute of Science and Technology, 39-1 Hawholgok-dong, Sungbuk-gu, Seoul, Korea
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7
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Choi YM, Kim SH, Chung S, Uhm DY, Park MK. Regional interaction of endoplasmic reticulum Ca2+ signals between soma and dendrites through rapid luminal Ca2+ diffusion. J Neurosci 2006; 26:12127-36. [PMID: 17122037 PMCID: PMC6675421 DOI: 10.1523/jneurosci.3158-06.2006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The endoplasmic reticulum (ER) Ca2+ store plays a key role in integration and conveyance of Ca2+ signals in highly polarized neurons. The interconnected ER network in neurons generates Ca2+ signals in local domains, but the regional interaction is unclear. Here, we show that continuous or repetitive applications of caffeine produced robust Ca2+ release from the ER Ca2+ store in dendritic areas without severe store depletion, but that similar stimuli applied to soma caused rapid store depletion in acutely isolated midbrain dopamine neurons. Partial emptying of the ER Ca2+ store within a dendrite caused a similar level of store depletion in unstimulated dendrites, as well as in soma. Photobleaching and local stimulation experiments revealed that Ca2+ and the dye trapped within the ER diffused rapidly from the soma to dendrites up to 90 microm, which we could resolve, suggesting that the ER network acts as a functional tunnel for rapid Ca2+ transport. These data imply that the ER in soma acts as a Ca2+ reservoir supplying Ca2+ to the dendritic store, and that the dendritic store, hence, is able to respond to Ca2+-mobilizing input signals endurably.
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Affiliation(s)
- Yu Mi Choi
- Department of Physiology, Sungkyunkwan University School of Medicine and Center For Molecular Medicine, Samsung Biomedical Research Institute, 300 Chunchun-dong, Jangan-ku, Suwon, 440-746, Korea
| | - Shin Hye Kim
- Department of Physiology, Sungkyunkwan University School of Medicine and Center For Molecular Medicine, Samsung Biomedical Research Institute, 300 Chunchun-dong, Jangan-ku, Suwon, 440-746, Korea
| | - Sungkwon Chung
- Department of Physiology, Sungkyunkwan University School of Medicine and Center For Molecular Medicine, Samsung Biomedical Research Institute, 300 Chunchun-dong, Jangan-ku, Suwon, 440-746, Korea
| | - Dae Yong Uhm
- Department of Physiology, Sungkyunkwan University School of Medicine and Center For Molecular Medicine, Samsung Biomedical Research Institute, 300 Chunchun-dong, Jangan-ku, Suwon, 440-746, Korea
| | - Myoung Kyu Park
- Department of Physiology, Sungkyunkwan University School of Medicine and Center For Molecular Medicine, Samsung Biomedical Research Institute, 300 Chunchun-dong, Jangan-ku, Suwon, 440-746, Korea
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8
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Chow FA, Anderson KA, Noeldner PK, Means AR. The autonomous activity of calcium/calmodulin-dependent protein kinase IV is required for its role in transcription. J Biol Chem 2005; 280:20530-8. [PMID: 15769749 DOI: 10.1074/jbc.m500067200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium/calmodulin-dependent kinase IV (CaMKIV) is a multifunctional serine/threonine kinase that is positively regulated by two main events. The first is the binding of calcium/calmodulin (Ca(2+)/CaM), which relieves intramolecular autoinhibition of the enzyme and leads to basal kinase activity. The second is activation by the upstream kinase, Ca(2+)/calmodulin-dependent kinase kinase. Phosphorylation of Ca(2+)/CaM-bound CaMKIV on its activation loop threonine (residue Thr(200) in human CaMKIV) by Ca(2+)/calmodulin-dependent kinase kinase leads to increased CaMKIV kinase activity. It has also been repeatedly noted that activation of CaMKIV is accompanied by the generation of Ca(2+)/CaM-independent or autonomous activity, although the significance of this event has been unclear. Here we demonstrate the importance of autonomous activity to CaMKIV biological function. We show that phosphorylation of CaMKIV on Thr(200) leads to the generation of a fully Ca(2+)/CaM-independent enzyme. By analyzing the behavior of wild-type and mutant CaMKIV proteins in biochemical experiments and cellular transcriptional assays, we demonstrate that CaMKIV autonomous activity is necessary and sufficient for CaMKIV-mediated transcription. The ability of wild-type CaMKIV to drive cAMP response element-binding protein-mediated transcription is strictly dependent upon an initiating Ca(2+) stimulus, which leads to kinase activation and development of autonomous activity in cells. Mutant CaMKIV proteins that are incapable of developing autonomous activity within a cellular context fail to drive transcription, whereas certain CaMKIV mutants that possess constitutive autonomous activity drive transcription in the absence of a Ca(2+) stimulus and independent of Ca(2+)/CaM binding or Thr(200) phosphorylation.
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Affiliation(s)
- Felice A Chow
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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9
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Verkhratsky A. Physiology and Pathophysiology of the Calcium Store in the Endoplasmic Reticulum of Neurons. Physiol Rev 2005; 85:201-79. [PMID: 15618481 DOI: 10.1152/physrev.00004.2004] [Citation(s) in RCA: 560] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The endoplasmic reticulum (ER) is the largest single intracellular organelle, which is present in all types of nerve cells. The ER is an interconnected, internally continuous system of tubules and cisterns, which extends from the nuclear envelope to axons and presynaptic terminals, as well as to dendrites and dendritic spines. Ca2+release channels and Ca2+pumps residing in the ER membrane provide for its excitability. Regulated ER Ca2+release controls many neuronal functions, from plasmalemmal excitability to synaptic plasticity. Enzymatic cascades dependent on the Ca2+concentration in the ER lumen integrate rapid Ca2+signaling with long-lasting adaptive responses through modifications in protein synthesis and processing. Disruptions of ER Ca2+homeostasis are critically involved in various forms of neuropathology.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester, Faculty of Biological Sciences, United Kingdom.
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10
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Trioulier Y, Torch S, Blot B, Cristina N, Chatellard-Causse C, Verna JM, Sadoul R. Alix, a Protein Regulating Endosomal Trafficking, Is Involved in Neuronal Death. J Biol Chem 2004; 279:2046-52. [PMID: 14585841 DOI: 10.1074/jbc.m309243200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alix/AIP1 is a cytoplasmic protein, which was first characterized as an interactor of ALG-2, a calcium-binding protein necessary for cell death. Alix has also recently been defined as a regulator of the endo-lysosomal system. Here we have used post-mitotic cerebellar neurons to test Alix function in caspase-dependent and -independent cell death. Indeed, these neurons survived when cultured in 25 mm potassium-containing medium but underwent apoptosis soon after the extracellular potassium was lowered to 5 mm. In agreement with other studies, we show that caspases are activated after K+ deprivation, but that inhibition of these proteases, using the pancaspase inhibitor boc-aspartyl(OMe)-fluoromethylketone, has no effect on cell survival. Transfection experiments demonstrated that Alix overexpression is sufficient to induce caspase activation, whereas overexpression of its C-terminal half, Alix-CT, blocks caspase activation and cell death after K+ deprivation. We also define a 12-amino acid PXY repeat of the C-terminal proline-rich domain necessary for binding ALG-2. Deletion of this domain in Alix or in Alix-CT abolished the effects of the overexpressed proteins on neuronal survival, demonstrating that the ALG-2-binding region is crucial for the death-modulating function of Alix. Overall, these findings define the Alix/ALG-2 complex as a regulator of cell death controlling both caspase-dependent and -independent pathways. They also suggest a molecular link between the endo-lysosomal system and the effectors of the cell death machinery.
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Affiliation(s)
- Yaël Trioulier
- Laboratoire Neurodégénérescence et Plasticité, INSERM-UJF, Pavillon de Neurologie, Hopital A. Michallon, 38043 Grenoble Cedex 9, France
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11
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Liang Y, Yuan LL, Johnston D, Gray R. Calcium signaling at single mossy fiber presynaptic terminals in the rat hippocampus. J Neurophysiol 2002; 87:1132-7. [PMID: 11826078 DOI: 10.1152/jn.00661.2001] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated internal Ca(2+) release at mossy fiber synapses on CA3 pyramidal neurons (mossy fiber terminals, MFTs) in the hippocampus. Presynaptic Ca(2+) influx was induced by giving a brief train of 20 stimuli at 100 Hz to the mossy fiber pathway. Using Ca(2+) imaging techniques, we recorded the Ca(2+) response as DeltaF/F, which increased rapidly with stimulation, but was often accompanied by a delayed peak that occurred after the train. The rise in presynaptic [Ca(2+)] could be completely blocked by application of 400 microM Cd(2+). Furthermore, the evoked Ca(2+) signals were reduced by group II mGluR agonists. Under the same experimental conditions, we investigated the effects of several agents on MFTs that disrupt regulation of intracellular Ca(2+) stores resulting in depletion of internal Ca(2+). We found that ryanodine, cyclopiazonic acid, thapsigargin, and ruthenium red all decreased both the early and the delayed increase in the Ca(2+) signals. We applied D,L-2-amino-5-phosphonovaleric acid (D,L-APV; 50 microM) and 6,7-Dinitroquinoxaline-2,3-dione (DNQX; 20 microM) to exclude the action of N-methyl-D-aspartate (NMDA) and non-NMDA receptors. Experiments with alternative lower affinity indicators for Ca(2+) (fura-2FF and calcium green-2) and the transient K(+) channel blocker, 4-aminopyridine were performed to control for the possible saturation of fura-2. Taken together, these results strongly support the hypothesis that the recorded terminals were from the mossy fibers of the dentate gyrus and suggest that a portion of the presynaptic Ca(2+) signal in response to brief trains of stimuli is due to release of Ca(2+) from internal stores.
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Affiliation(s)
- Yong Liang
- Division of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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12
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Gardiol A, Racca C, Triller A. RNA transport and local protein synthesis in the dendritic compartment. Results Probl Cell Differ 2001; 34:105-28. [PMID: 11288671 DOI: 10.1007/978-3-540-40025-7_7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- A Gardiol
- Laboratoire de Biologie Cellulaire de la Synapse N&P INSERM U497 Ecole Normale Supérieure, 46 rue d'Ulm, 75005 Paris, France
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13
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Galvani A, Sperling L. Regulation of secretory protein gene expression in paramecium role of the cortical exocytotic sites. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:3226-34. [PMID: 10824107 DOI: 10.1046/j.1432-1327.2000.01341.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In cells that possess a regulated secretory pathway, exocytosis can lead to transcriptional activation of genes encoding products stored in secretory granules as well as genes required for granule biogenesis. With the objective of understanding this response, we have examined the expression of Paramecium secretory protein genes in different physiological and genetic contexts. The genes belong to the trichocyst matrix protein (TMP) multigene family, encoding polypeptides that form the crystalline matrix of the secretory granules, known as trichocysts. Approximately 1000 trichocysts per cell are docked at pre-formed cortical exocytotic sites. Their rapid and synchronous exocytosis can be triggered by vital secretagogues such as aminoethyldextran without harming the cells. Using this exocytotic trigger, we found that the transcription of TMP genes undergoes rapid, transient and co-ordinate 10-fold activation in response to massive exocytosis, leading to a 2.5-fold increase in the pool of TMP mRNA. Experiments with exocytosis-deficient mutants show that the secretagogue-induced increase in intracellular free calcium implicated in stimulus/secretion coupling is not sufficient to activate TMP gene expression. We present evidence that the state of occupation of the cortical exocytotic sites can affect TMP gene expression and suggest that these sites play a role in gene activation in response to exocytosis.
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Affiliation(s)
- A Galvani
- Centre de Génétique Moléculaire, CNRS, Gif-sur-Yvette, France
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14
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García-Palomero E, Montiel C, Herrero CJ, García AG, Alvarez RM, Arnalich FM, Renart J, Lara H, Cárdenas AM. Multiple calcium pathways induce the expression of SNAP-25 protein in chromaffin cells. J Neurochem 2000; 74:1049-58. [PMID: 10693936 DOI: 10.1046/j.1471-4159.2000.0741049.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Incubation of bovine adrenal chromaffin cells in high K+ (38 mM) during 24-48 h enhanced 2.5 to five times the expression of SNAP-25 protein and mRNA, respectively. This increase was reduced 86% by furnidipine (an L-type Ca2+ channel blocker) but was unaffected by either omega-conotoxin GVIA (an N-type Ca2+ channel blocker) or -agatoxin IVA (a P/Q-type Ca2+ channel blocker). Combined blockade of N and P/Q channels with omega-conotoxin MVIIC did, however, block by 76% the protein expression. The inhibitory effects of fumidipine were partially reversed when the external Ca2+ concentration was raised from 1.6 to 5 mM. These findings, together with the fact that nicotinic receptor activation or Ca2+ release from internal stores also enhanced SNAP-25 protein expression, suggest that an increment of cytosolic Ca2+ concentration ([Ca2+]), rather than its source or Ca2+ entry pathway, is the critical signal to induce the protein expression. The greater coupling between L-type Ca2+ channels and protein expression might be due to two facts: (a) L channels contributed 50% to the global [Ca2+]i rise induced by 38 mM K+ in indo-1-loaded chromaffin cells and (b) L channels undergo less inactivation than N or P/Q channels on sustained stimulation of these cells.
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Affiliation(s)
- E García-Palomero
- Instituto de Farmacología Teófilo Hernando, Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Spain
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Zhao W, Meiri N, Xu H, Cavallaro S, Quattrone A, Zhang L, Alkon DL. Spatial learning induced changes in expression of the ryanodine type II receptor in the rat hippocampus. FASEB J 2000; 14:290-300. [PMID: 10657985 DOI: 10.1096/fasebj.14.2.290] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Calcium signaling critical to neural functions is mediated through Ca(2+) channels localized on both the plasma membrane and intracellular organelles such as endoplasmic reticulum. Whereas Ca(2+) influx occurs via the voltage- or/and ligand-sensitive Ca(2+) channels, Ca(2+) release from intracellular stores that amplifies further the Ca(2+) signal is thought to be involved in more profound and lasting changes in neurons. The ryanodine receptor, one of the two major intracellular Ca(2+) channels, has been an important target for studying Ca(2+) signaling in brain functions, including learning and memory, due to its characteristic Ca(2+)-induced Ca(2+) release. In this study, we report regional and cellular distributions of the type-2 ryanodine receptor (RyR2) mRNA in the rat brain, and effects of spatial learning on RyR2 gene expression at mRNA and protein levels in the rat hippocampus. Using in situ hybridization, reverse transcription polymerase chain reaction, and ribonuclease protection assays, significant increases in RyR2 mRNA were found in the hippocampus of rats trained in an intensive water maze task. With immunoprecipitation and immunoblotting, protein levels of RyR2 were also demonstrated to be increased in the microsomal fractions prepared from hippocampi of trained rats. These results suggest that RyR2, and hence the RyR2-mediated Ca(2+) signals, may be involved in memory processing after spatial learning. The increases in RyR2 mRNA and protein at 12 and 24 h after training could contribute to more permanent changes such as structural modifications during long-term memory storage. Zhao, W., Meiri, N., Xu, H., Cavallaro, S., Quattrone, A., Zhang, L., Alkon, D. A. Spatial learning induced changes in expression of the ryanodine type II receptor in the rat hippocampus.
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Affiliation(s)
- W Zhao
- Laboratory of Adaptive Systems, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
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16
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Abstract
Calcium signals appear throughout the first 24 hours of zebrafish development. These begin at egg activation, then continue to be generated throughout the subsequent zygote, cleavage, blastula, gastrula, and segmentation periods. They are thus associated with the major phases of pattern formation: cell proliferation, cell differentiation, axis determination, the generation of primary germ layers, the emergence of rudimentary organ systems, and therefore the establishment of the basic vertebrate body plan. When signals need to be transmitted across significant distances they take the form of waves, either intracellular waves when the cell size is large, or later in development when the cell size is reduced, intercellular waves. We will consider both types of calcium signals and their integration into signalling networks, and discuss their possible functions and developmental significance with regard to pattern formation. BioEssays 22:113-123, 2000.
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Affiliation(s)
- S E Webb
- Department of Biology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PRC
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17
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van Der Luit AH, Olivari C, Haley A, Knight MR, Trewavas AJ. Distinct calcium signaling pathways regulate calmodulin gene expression in tobacco. PLANT PHYSIOLOGY 1999; 121:705-14. [PMID: 10557218 PMCID: PMC59432 DOI: 10.1104/pp.121.3.705] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/1999] [Accepted: 07/20/1999] [Indexed: 05/17/2023]
Abstract
Cold shock and wind stimuli initiate Ca(2+) transients in transgenic tobacco (Nicotiana plumbaginifolia) seedlings (named MAQ 2.4) containing cytoplasmic aequorin. To investigate whether these stimuli initiate Ca(2+) pathways that are spatially distinct, stress-induced nuclear and cytoplasmic Ca(2+) transients and the expression of a stress-induced calmodulin gene were compared. Tobacco seedlings were transformed with a construct that encodes a fusion protein between nucleoplasmin (a major oocyte nuclear protein) and aequorin. Immunocytochemical evidence indicated targeting of the fusion protein to the nucleus in these plants, which were named MAQ 7.11. Comparison between MAQ 7.11 and MAQ 2.4 seedlings confirmed that wind stimuli and cold shock invoke separate Ca(2+) signaling pathways. Partial cDNAs encoding two tobacco calmodulin genes, NpCaM-1 and NpCaM-2, were identified and shown to have distinct nucleotide sequences that encode identical polypeptides. Expression of NpCaM-1, but not NpCaM-2, responded to wind and cold shock stimulation. Comparison of the Ca(2+) dynamics with NpCaM-1 expression after stimulation suggested that wind-induced NpCaM-1 expression is regulated by a Ca(2+) signaling pathway operational predominantly in the nucleus. In contrast, expression of NpCaM-1 in response to cold shock is regulated by a pathway operational predominantly in the cytoplasm.
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Affiliation(s)
- A H van Der Luit
- Institute for Molecular Cell Biology, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam, The Netherlands.
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18
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Mulvaney JM, Zhang T, Fewtrell C, Roberson MS. Calcium influx through L-type channels is required for selective activation of extracellular signal-regulated kinase by gonadotropin-releasing hormone. J Biol Chem 1999; 274:29796-804. [PMID: 10514457 DOI: 10.1074/jbc.274.42.29796] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The hypothalamic decapeptide gonadotropin-releasing hormone stimulates mobilization of two discrete pools of calcium in clonal (alphaT3-1) and primary pituitary gonadotropes. A multidisciplinary approach was implemented to investigate the effects of discrete calcium fluctuations on the signaling pathways linking the gonadotropin-releasing hormone receptor to activation of mitogen-activated protein kinases and immediate early genes. Blockade of calcium influx through nifedipine-sensitive voltage-gated calcium channels reduced buserelin-induced activation of extracellular signal-regulated kinase (ERK) and c-Fos while activation of c-Jun N-terminal kinase and c-Jun was unaffected. Inhibition of buserelin-stimulated ERK activity by nifedipine was also observed in rat pituitary cells in primary culture. Direct activation of alphaT3-1 cell L-type calcium channels with the agonist Bay-K 8644 resulted in phosphorylation of ERK and induction of c-Fos. However, simple voltage-induced channel activation did not produce a sufficient calcium signal, since depolarization with 35 mM KCl failed to induce activation of ERK. Depletion of intracellular calcium stores with thapsigargin did not affect buserelin-induced ERK activation. An inhibitor of protein kinase C decreased calcium influx through nifedipine-sensitive calcium channels and phosphorylation of ERK induced by buserelin. Pharmacological inhibition of protein kinase C did not block Bay-K 8644-induced ERK activation. These observations suggest that calcium influx through L-type channels is required for GnRH-induced activation of ERK and c-Fos and that the influence of calcium lies downstream of protein kinase C.
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Affiliation(s)
- J M Mulvaney
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
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19
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Chen L, Bao S, Qiao X, Thompson RF. Impaired cerebellar synapse maturation in waggler, a mutant mouse with a disrupted neuronal calcium channel gamma subunit. Proc Natl Acad Sci U S A 1999; 96:12132-7. [PMID: 10518588 PMCID: PMC18424 DOI: 10.1073/pnas.96.21.12132] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The waggler, a neurological mutant mouse with a disrupted putative neuronal Ca(2+) channel gamma subunit, exhibits a cerebellar granule cell-specific brain-derived neurotrophic factor deficit, severe ataxia, and impaired eyeblink conditioning. Here, we show that multiple synapses of waggler cerebellar granule cells are arrested at an immature stage during development. Synaptic transmission is reduced at parallel fiber-Purkinje cell synapses. The Golgi cell-granule cell synaptic currents show immature kinetics associated with reduced gamma-aminobutyric acid type A receptor alpha6 subunit expression in granule cells. In addition, the mossy fiber-granule cell synapses exhibit N-methyl-D-aspartate (NMDA) receptor-mediated excitatory postsynaptic currents (EPSCs), but not alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated EPSCs. Our results suggest that voltage-dependent Ca(2+) channels are involved in synapse maturation. This deficient synaptic transmission in the waggler cerebellum may account for their behavioral deficits.
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Affiliation(s)
- L Chen
- Neuroscience Program, University of Southern California, Los Angeles, CA 90089-2520, USA
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20
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Curtis J, Finkbeiner S. Sending signals from the synapse to the nucleus: Possible roles for CaMK, Ras/ERK, and SAPK pathways in the regulation of synaptic plasticity and neuronal growth. J Neurosci Res 1999. [DOI: 10.1002/(sici)1097-4547(19991001)58:1<88::aid-jnr9>3.0.co;2-r] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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21
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Studzinski DM, Callahan RE, Benjamins JA. Increased intracellular calcium alters myelin gene expression in the N20.1 oligodendroglial cell line. J Neurosci Res 1999. [DOI: 10.1002/(sici)1097-4547(19990901)57:5<633::aid-jnr5>3.0.co;2-i] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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22
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Ca(2+)-permeable AMPA receptors induce phosphorylation of cAMP response element-binding protein through a phosphatidylinositol 3-kinase-dependent stimulation of the mitogen-activated protein kinase signaling cascade in neurons. J Neurosci 1999. [PMID: 10407026 DOI: 10.1523/jneurosci.19-14-05861.1999] [Citation(s) in RCA: 143] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Ca(2+)-permeable AMPA receptors may play a key role during developmental neuroplasticity, learning and memory, and neuronal loss in a number of neuropathologies. However, the intracellular signaling pathways used by AMPA receptors during such processes are not fully understood. The mitogen-activated protein kinase (MAPK) cascade is an attractive target because it has been shown to be involved in gene expression, synaptic plasticity, and neuronal stress. Using primary cultures of mouse striatal neurons and a phosphospecific MAPK antibody we addressed whether AMPA receptors can activate the MAPK cascade. We found that in the presence of cyclothiazide, AMPA caused a robust and direct (no involvement of NMDA receptors or L-type voltage-sensitive Ca(2+) channels) Ca(2+)-dependent activation of MAPK through MAPK kinase (MEK). This activation was blocked by GYKI 53655, a noncompetitive selective antagonist of AMPA receptors. Probing the mechanism of this activation revealed an essential role for phosphatidylinositol 3-kinase (PI 3-kinase) and the involvement of a pertussis toxin (PTX)-sensitive G-protein, a Src family protein tyrosine kinase, and Ca(2+)/calmodulin-dependent kinase II. Similarly, kainate activated MAPK in a PI 3-kinase-dependent manner. AMPA receptor-evoked neuronal death and arachidonic acid mobilization did not appear to involve signaling through the MAPK pathway. However, AMPA receptor stimulation led to a Ca(2+)-dependent phosphorylation of the nuclear transcription factor CREB, which could be prevented by inhibitors of MEK or PI 3-kinase. Our results indicate that Ca(2+)-permeable AMPA receptors transduce signals from the cell surface to the nucleus of neurons through a PI 3-kinase-dependent activation of MAPK. This novel pathway may play a pivotal role in regulating synaptic plasticity in the striatum.
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23
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Craske M, Takeo T, Gerasimenko O, Vaillant C, Török K, Petersen OH, Tepikin AV. Hormone-induced secretory and nuclear translocation of calmodulin: oscillations of calmodulin concentration with the nucleus as an integrator. Proc Natl Acad Sci U S A 1999; 96:4426-31. [PMID: 10200278 PMCID: PMC16348 DOI: 10.1073/pnas.96.8.4426] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many important enzyme activities are regulated by Ca2+-dependent interactions with calmodulin (CaM). Some of the most important targets for CaM action are in the nucleus, and Ca2+-dependent CaM translocation into this organelle has been reported. Hormone-evoked cytosolic Ca2+ signals occur physiologically as oscillations, but, so far, oscillations in CaM concentration have not been described. We loaded fluorescent-labeled CaM into pancreatic acinar cells and monitored the fluorescence in various regions by confocal microscopy. Sustained high concentrations of the hormone cholecystokinin or the neurotransmitter acetylcholine evoked a transient movement of cytosolic CaM from the basal nonnuclear area into the secretory granule region and, thereafter, a more substantial and prolonged translocation of CaM into the nucleoplasm. About 50% of the CaM that bound Ca2+ translocated. At a lower hormone concentration, evoking Ca2+ oscillations, regular spikes of increased CaM concentration were seen in the secretory granule region with mirror image spikes of decreased CaM concentration in the basal nonnuclear region. The nucleus was able to integrate the Ca2+ spike-evoked pulses of CaM translocation into a sustained elevation of the nucleoplasmic concentration of this protein.
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Affiliation(s)
- M Craske
- Medical Research Council Secretory Control Research Group, Physiological Laboratory, University of Liverpool, Liverpool L69 3BX, United Kingdom
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24
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Wigle D, Ho W, Lo D, Francis J, Eubanks JH, Wallace MC. Altered expression levels of SEF-2 and p112 in the rat hippocampus after transient cerebral ischemia: identification by mRNA differential display. J Cereb Blood Flow Metab 1999; 19:435-42. [PMID: 10197513 DOI: 10.1097/00004647-199904000-00009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The authors used mRNA differential display to identify genes whose expression levels are altered in the adult rat hippocampus 24 hours after global ischemia. At this time after challenge, the basic helix-loop-helix transcription factor, SEF-2, and the 26S proteasome complex subunit, p112, were identified as genes whose expression levels are decreased and increased, respectively, in the hippocampus. To determine the spatial and temporal patterns of expression change for each gene, the authors antisense in situ hybridization to paired brain sections of sham-operated and global ischemia-challenged rats at 6, 12, and 24 hours after reperfusion SEF-2 expression was not significantly altered from that of sham-operated controls in any hippocampal subfield at or before 12 hours after challenge. At 24 hours after ischemia, however, SEF-2 expression levels were significantly diminished in the vulnerable CA1 subfield, but not in the less vulnerable CA3 or dentate granule cell subfields. The proteasome p112 subunit gene displayed no change in expression levels at 6 hours after insult; however, an elevated expression was observed at 12 hours after challenge in the dentate granule cell subfield. By 24 hours after challenge, p112 expression was significantly elevated in both the CA1 and dentate granule cell subfields. These results demonstrate that a member of the basic helix-loop-helix family of transcription factors, SEF-2, and the major subunit of the 26S proteasome complex, p112, display altered gene expression in the hippocampus after transient cerebral ischemia.
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Affiliation(s)
- D Wigle
- Playfair Neuroscience Unit, University of Toronto, Ontario, Canada
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25
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Alkon DL, Nelson TJ, Zhao W, Cavallaro S. Time domains of neuronal Ca2+ signaling and associative memory: steps through a calexcitin, ryanodine receptor, K+ channel cascade. Trends Neurosci 1998; 21:529-37. [PMID: 9881851 DOI: 10.1016/s0166-2236(98)01277-6] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Synaptic changes that underlie associative learning and memory begin with temporally related activity of two or more independent synaptic inputs to common postsynaptic targets. In turn, temporally related molecular events regulate cytosolic Ca2+ during progressively longer-lasting time domains. Associative learning behaviors of living animals have been correlated with changes of neuronal voltage-dependent K+ currents, protein kinase C-mediated phosphorylation and synthesis of the Ca2+ and GTP-binding protein, calexcitin (CE),and increased expression of the Ca2+-releasing ryanodine receptor (type II). These molecular events, some of which have been found to be dysfunctional in Alzheimer's disease, provide means of altering dendritic excitability and thus synaptic efficacy during induction, consolidation and storage of associative memory. Apparently, such stages of behavioral learning correspond to sequential differences of Ca2+ signaling that could occur in spatially segregated dendritic compartments distributed across brain structures, such as the hippocampus.
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Affiliation(s)
- D L Alkon
- Laboratory of Adaptive Systems, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892-4012, USA
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26
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Franz C, Durussel I, Cox JA, Schäfer BW, Heizmann CW. Binding of Ca2+ and Zn2+ to human nuclear S100A2 and mutant proteins. J Biol Chem 1998; 273:18826-34. [PMID: 9668057 DOI: 10.1074/jbc.273.30.18826] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The Ca2+-binding protein S100A2 is an unusual member of the S100 family, characterized by its nuclear localization and down-regulated expression in tumorigenic cells. In this study, we investigated the properties of human recombinant S100A2 (wtS100A2) and of two mutants in which the amino-terminal Ca2+-binding site I (N mutant) and in addition the carboxyl-terminal site II (NC mutant) were replaced by the canonical loop (EF-site) of alpha-parvalbumin. Size exclusion chromatography and circular dichroism showed that, irrespective of the state of cation binding, wtS100A2 and mutants are dimers and rich in alpha-helical structure. Flow dialysis revealed that wtS100A2 binds four Ca2+ atoms per dimer with pronounced positive cooperativity. Both mutants also bind four Ca2+ atoms but with a higher affinity than wtS100A2 and with negative cooperativity. The binding of the first two Ca2+ ions to the N mutant occurred with 100-fold higher affinity than in wtS100A2 and a 2-fold increase for the last two Ca2+ ions. A further 2-3-fold increase of affinity was observed for respective binding steps of the NC mutant. The Hummel-Dryer method demonstrated that the wild type and mutants bind four Zn2+ atoms per dimer with similar affinity. Fluorescence and difference spectrophotometry showed that the binding of Ca2+ and Zn2+ induces considerable conformational changes, mostly attributable to changes in the microenvironment of Tyr76 located in site II. Fluorescence enhancement of 4,4'-dianilino-1, 1'-binaphthyl-5,5'-disulfonic acid clearly indicated that Ca2+ and Zn2+ binding induce a hydrophobic patch at the surface of wtS100A2, which, as in calmodulin, may be instrumental for the regulatory role of S100A2 in the nucleus.
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Affiliation(s)
- C Franz
- Department of Pediatrics, Division of Clinical Chemistry and Biochemistry, University of Zürich, CH-8032 Zürich, Switzerland
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27
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Affiliation(s)
- M J Berridge
- The Babraham Institute, Babraham Laboratory of Molecular Signalling, Cambridge, United Kingdom
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