151
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Crews L, Masliah E. Molecular mechanisms of neurodegeneration in Alzheimer's disease. Hum Mol Genet 2010; 19:R12-20. [PMID: 20413653 PMCID: PMC2875049 DOI: 10.1093/hmg/ddq160] [Citation(s) in RCA: 510] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 04/19/2010] [Indexed: 12/20/2022] Open
Abstract
Alzheimer's disease (AD) is characterized by cognitive impairment, progressive neurodegeneration and formation of amyloid-beta (Abeta)-containing plaques and neurofibrillary tangles composed of hyperphosphorylated tau. The neurodegenerative process in AD is initially characterized by synaptic damage accompanied by neuronal loss. In addition, recent evidence suggests that alterations in adult neurogenesis in the hippocampus might play a role. Synaptic loss is one of the strongest correlates to the cognitive impairment in patients with AD. Several lines of investigation support the notion that the synaptic pathology and defective neurogenesis in AD are related to progressive accumulation of Abeta oligomers rather than fibrils. Abnormal accumulation of Abeta resulting in the formation of toxic oligomers is the result of an imbalance between the levels of Abeta production, aggregation and clearance. Abeta oligomers might lead to synaptic damage by forming pore-like structures with channel activity; alterations in glutamate receptors; circuitry hyper-excitability; mitochondrial dysfunction; lysosomal failure and alterations in signaling pathways related to synaptic plasticity, neuronal cell and neurogenesis. A number of signaling proteins, including fyn kinase; glycogen synthase kinase-3beta (GSK3beta) and cyclin-dependent kinase-5 (CDK5), are involved in the neurodegenerative progression of AD. Therapies for AD might require the development of anti-aggregation compounds, pro-clearance pathways and blockers of hyperactive signaling pathways.
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Affiliation(s)
| | - Eliezer Masliah
- Department of Pathology and
- Department of Neurosciences, University of California – San Diego, 9500 Gilman Drive, La Jolla, CA 92003-0624, USA
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152
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de Thonel A, Ferraris SE, Pallari HM, Imanishi SY, Kochin V, Hosokawa T, Hisanaga SI, Sahlgren C, Eriksson JE. Protein kinase Czeta regulates Cdk5/p25 signaling during myogenesis. Mol Biol Cell 2010; 21:1423-34. [PMID: 20200223 PMCID: PMC2854099 DOI: 10.1091/mbc.e09-10-0847] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Atypical protein kinase Cζ (PKCζ) is emerging as a mediator of differentiation. Here, we describe a critical role for PKCζ during myogenic differentiation. Our results identify PKCζ as a controller of myogenic differentiation by its regulation of Cdk5. Atypical protein kinase Cζ (PKCζ) is emerging as a mediator of differentiation. Here, we describe a novel role for PKCζ in myogenic differentiation, demonstrating that PKCζ activity is indispensable for differentiation of both C2C12 and mouse primary myoblasts. PKCζ was found to be associated with and to regulate the Cdk5/p35 signaling complex, an essential factor for both neuronal and myogenic differentiation. Inhibition of PKCζ activity prevented both myotube formation and simultaneous reorganization of the nestin intermediate filament cytoskeleton, which is known to be regulated by Cdk5 during myogenesis. p35, the Cdk5 activator, was shown to be a specific phosphorylation target of PKCζ. PKCζ-mediated phosphorylation of Ser-33 on p35 promoted calpain-mediated cleavage of p35 to its more active and stable fragment, p25. Strikingly, both calpain activation and the calpain-mediated cleavage of p35 were shown to be PKCζ-dependent in differentiating myoblasts. Overall, our results identify PKCζ as a controller of myogenic differentiation by its regulation of the phosphorylation-dependent and calpain-mediated p35 cleavage, which is crucial for the amplification of the Cdk5 activity that is required during differentiation.
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Affiliation(s)
- Aurélie de Thonel
- Turku Centre for Biotechnology, University of Turku and Abo Akademi University, 20521 Turku, Finland
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153
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Hanger DP, Seereeram A, Noble W. Mediators of tau phosphorylation in the pathogenesis of Alzheimer's disease. Expert Rev Neurother 2010; 9:1647-66. [PMID: 19903024 DOI: 10.1586/ern.09.104] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The need for disease-modifying drugs for Alzheimer's disease has become increasingly important owing to escalating disease prevalence and the associated socio-economic burden. Until recently, reducing brain amyloid accumulation has been the main therapeutic focus; however, increasing evidence suggests that targeting abnormal tau phosphorylation could be beneficial. Tau is phosphorylated by several protein kinases and this is balanced by dephosphorylation by protein phosphatases. Phosphorylation at specific sites can influence the physiological functions of tau, including its role in binding to and stabilizing the neuronal cytoskeleton. aberrant phosphorylation of tau could render it susceptible to potentially pathogenic alterations, including conformational changes, proteolytic cleavage and aggregation. While strategies that reduce tau phosphorylation in transgenic models of disease have been promising, our understanding of the mechanisms through which tau becomes abnormally phosphorylated in disease is lacking.
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Affiliation(s)
- Diane P Hanger
- MRC Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry, Department of Neuroscience (P037), De Crespigny Park, London SE5 8AF, UK.
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154
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Kanungo J, Zheng YL, Amin ND, Pant HC. Targeting Cdk5 activity in neuronal degeneration and regeneration. Cell Mol Neurobiol 2009; 29:1073-80. [PMID: 19455415 PMCID: PMC5603152 DOI: 10.1007/s10571-009-9410-6] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Accepted: 04/29/2009] [Indexed: 10/20/2022]
Abstract
The major priming event in neurodegeneration is loss of neurons. Loss of neurons by apoptotic mechanisms is a theme for studies focused on determining therapeutic strategies. Neurons following an insult, activate a number of signal transduction pathways, of which, kinases are the leading members. Cyclin-dependent kinase 5 (Cdk5) is one of the kinases that have been linked to neurodegeneration. Cdk5 along with its principal activator p35 is involved in multiple cellular functions ranging from neuronal differentiation and migration to synaptic transmission. However, during neurotoxic stress, intracellular rise in Ca(2+) activates calpain, which cleaves p35 to generate p25. The long half-life of Cdk5/p25 results in a hyperactive, aberrant Cdk5 that hyperphosphorylates Tau, neurofilament and other cytoskeletal proteins. These hyperphosphorylated cytoskeletal proteins set the groundwork to forming neurofibrillary tangles and aggregates of phosphorylated proteins, hallmarks of neurodegenerative diseases like Alzheimer's disease, Parkinson's disease and Amyotropic Lateral Sclerosis. Attempts to selectively target Cdk5/p25 activity without affecting Cdk5/p35 have been largely unsuccessful. A polypeptide inhibitor, CIP (Cdk5 inhibitory peptide), developed in our laboratory, successfully inhibits Cdk5/p25 activity in vitro, in cultured primary neurons, and is currently undergoing validation tests in mouse models of neurodegeneration. Here, we discuss the therapeutic potential of CIP in regenerating neurons that are exposed to neurodegenerative stimuli.
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Affiliation(s)
- Jyotshnabala Kanungo
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bldg. 49, Rm 2A28, 9000 Rockville Pike, Bethesda, MD 20892 USA
| | - Ya-li Zheng
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bldg. 49, Rm 2A28, 9000 Rockville Pike, Bethesda, MD 20892 USA
| | - Niranjana D. Amin
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bldg. 49, Rm 2A28, 9000 Rockville Pike, Bethesda, MD 20892 USA
| | - Harish C. Pant
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bldg. 49, Rm 2A28, 9000 Rockville Pike, Bethesda, MD 20892 USA
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155
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Tobias A, Saxena M, Lelievre V. CDK5: the "pathfinder" for new born neurons in adult hippocampus? Cell Adh Migr 2009; 3:319-21. [PMID: 19855173 DOI: 10.4161/cam.3.4.9951] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Neurogenesis takes place in the mammalian hippocampus throughout the whole life and deficient adult hippocampal neurogenesis has been related to neurological conditions like Alzheimer disease (AD), Parkinson disease (PD) and epilepsy. The molecular mechanisms by which immature neurons and their extending neurites find their appropriate position and target area remain largely unknown. Recent work by Jessberger et al. examines the role of Cdk5 in normal adult neurogenesis by a retroviral knock-down approach. Cdk5 is shown to be implicated in the migration of newborn neurons into the granule cell layer (GCL), as well as, in correct targeting of dendrites from newborn granule cells (GC) into the molecular layer (ML) of the dentate gyrus (DG). The study also shows that aberrant dendrites still seem to become synaptically integrated into the existing circuitry thereby suggesting a mechanistic dissociation between accurate dendritic targeting and subsequent synapse formation. The finding of Cdk5 guiding this integration of new born neurons at the physiologically appropriate place is an important step towards understanding adult neurogenesis that may help to overcome problems with the restorative use of neural stem cells in present grafting approaches in neurological diseases.
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Affiliation(s)
- Albert Tobias
- Faculté des Sciences de la Vie, Unìversité de Strasbourg, Strasbourg, France
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156
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Abstract
Aberrant cell cycle activity and DNA damage have been observed in neurons in association with various neurodegenerative conditions. While there is strong evidence for a causative role for these events in neurotoxicity, it is unclear how they are triggered and why they are toxic. Here, we introduce a brief background of the current view on cell cycle activity and DNA damage in neurons and speculate on their relevance to neuronal survival. Furthermore, we suggest that the two events may be triggered in common by deregulation of fundamental processes, such as chromatin modulation, which are required for maintaining both DNA integrity and proper regulation of cell cycle gene expression.
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Affiliation(s)
- Dohoon Kim
- Department of Brain and Cognitive Sciences, Howard Hughes Medical Institute, Cambridge, Massachusetts 01239, USA
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157
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Jessberger S, Gage FH, Eisch AJ, Lagace DC. Making a neuron: Cdk5 in embryonic and adult neurogenesis. Trends Neurosci 2009; 32:575-82. [PMID: 19782409 DOI: 10.1016/j.tins.2009.07.002] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Revised: 07/06/2009] [Accepted: 07/07/2009] [Indexed: 01/02/2023]
Abstract
Cyclin-dependent kinase 5 (Cdk5) has been implicated in the migration, maturation and survival of neurons born during embryonic development. New evidence suggests that Cdk5 has comparable but also distinct functions in adult neurogenesis. Here we summarize accumulating evidence on the role of Cdk5 in regulation of the cell cycle, migration, survival, maturation and neuronal integration. We specifically highlight the many similarities and few tantalizing differences in the roles of Cdk5 in the embryonic and adult brain. We discuss the signaling pathways that might contribute to Cdk5 action in regulating embryonic and adult neurogenesis, highlighting future research directions that will help to clarify the mechanisms underlying lifelong neurogenesis in the mammalian brain.
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Affiliation(s)
- Sebastian Jessberger
- Institute of Cell Biology, Department of Biology, ETH Zurich, Schafmattstrasse 18, 8093 Zurich, Switzerland.
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158
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Sun KH, Lee HG, Smith MA, Shah K. Direct and indirect roles of cyclin-dependent kinase 5 as an upstream regulator in the c-Jun NH2-terminal kinase cascade: relevance to neurotoxic insults in Alzheimer's disease. Mol Biol Cell 2009; 20:4611-9. [PMID: 19776350 DOI: 10.1091/mbc.e09-05-0433] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Significant increase in JNK, c-Jun, and Cdk5 activities are reported in Alzheimer's disease (AD). Inhibition of c-Jun prevents neuronal cell death in in vivo AD models, highlighting it as a major JNK effector. Both JNK and Cdk5 promote neurodegeneration upon deregulation; however, Cdk5 has not been mechanistically linked to JNK or c-Jun. This study presents the first mechanism showing Cdk5 as a major regulator of the JNK cascade. Deregulated Cdk5 induces biphasic activation of JNK pathway. The first phase revealed c-Jun as a direct substrate of Cdk5, whose activation is independent of reactive oxygen species (ROS) and JNK. In the second phase, Cdk5 activates c-Jun via ROS-mediated activation of JNK. Rapid c-Jun activation is supported by in vivo data showing c-Jun phosphorylation in cerebral cortex upon p25 induction in transgenic mice. Cdk5-mediated biphasic activation of c-Jun highlights c-Jun, rather than JNK, as an important therapeutic target, which was confirmed in neuronal cells. Finally, Cdk5 inhibition endows superior protection against neurotoxicity, suggesting that Cdk5 is a preferable therapeutic target for AD relative to JNK and c-Jun.
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Affiliation(s)
- Kai-Hui Sun
- Department of Chemistry and Purdue Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
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159
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Lai KO, Ip NY. Recent advances in understanding the roles of Cdk5 in synaptic plasticity. Biochim Biophys Acta Mol Basis Dis 2009; 1792:741-5. [DOI: 10.1016/j.bbadis.2009.05.001] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2008] [Revised: 05/03/2009] [Accepted: 05/05/2009] [Indexed: 01/05/2023]
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160
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Satyanarayana A, Kaldis P. Mammalian cell-cycle regulation: several Cdks, numerous cyclins and diverse compensatory mechanisms. Oncogene 2009; 28:2925-39. [PMID: 19561645 DOI: 10.1038/onc.2009.170] [Citation(s) in RCA: 552] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
After a decade of extensive work on gene knockout mouse models of cell-cycle regulators, the classical model of cell-cycle regulation was seriously challenged. Several unexpected compensatory mechanisms were uncovered among cyclins and Cdks in these studies. The most astonishing observation is that Cdk2 is dispensable for the regulation of the mitotic cell cycle with both Cdk4 and Cdk1 covering for Cdk2's functions. Similar to yeast, it was recently discovered that Cdk1 alone can drive the mammalian cell cycle, indicating that the regulation of the mammalian cell cycle is highly conserved. Nevertheless, cell-cycle-independent functions of Cdks and cyclins such as in DNA damage repair are still under investigation. Here we review the compensatory mechanisms among major cyclins and Cdks in mammalian cell-cycle regulation.
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Affiliation(s)
- A Satyanarayana
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA.
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161
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Identification of non-muscle myosin heavy chain as a substrate for Cdk5 and tool for drug screening. J Biomed Sci 2009; 16:55. [PMID: 19534817 PMCID: PMC2703631 DOI: 10.1186/1423-0127-16-55] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Accepted: 06/17/2009] [Indexed: 02/04/2023] Open
Abstract
Background Deregulated activation of cyclin-dependent kinase-5 (Cdk5) is implicated in neurodegenerative disorders such as Alzheimer's disease. One of the restricting factors for developing specific Cdk5 inhibitors is the lack of reproducible and well-characterized cellular in vitro assay systems. Methods HEK293 cells were transfected with Cdk5 and its activator p25 as a starting point for an assay to screen for Cdk5 kinase inhibitors. To identify suitable substrates for Cdk5 we utilized an antibody that recognizes phospho serine in a consensus motif for Cdk substrates. Results Western blot analysis of transfected cells detected a 200 kDa band that was identified, by mass spectrometry, as non-muscle myosin heavy chain, type B (NMHC-B). Phosphorylation of NMHC-B was evident only in cells that were double transfected with Cdk5/p25 and was dose-dependently inhibited by Roscovitine and other Cdk5 inhibitors. Cdk5 was found to phosphorylate NMHC-B also in the human neuroblastoma SH-SY5Y cell line. Conclusion A novel Cdk5 substrate NMHC-B was identified in this study. A cellular assay for screening of Cdk5 inhibitors was established using NMHC-B phosphorylation as a read-out in Cdk5/p25 transfected HEK293 cells. A novel Cdk5 inhibitor was also pharmacologically characterized in this assay system.
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162
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Kissler AE, Pettersson N, Frölich A, Sigrist SJ, Suter B. Drosophila cdk5 is needed for locomotive behavior and NMJ elaboration, but seems dispensable for synaptic transmission. Dev Neurobiol 2009; 69:365-77. [PMID: 19263480 DOI: 10.1002/dneu.20711] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cyclin-dependent kinase 5 (Cdk5) functions in postmitotic neuronal cells and play roles in cell differentiation, cell migration, axonal guidance, and synaptic function. Here, we demonstrate that Drosophila cdk5 is dispensable for adult viability and fertility, a feature that allows us to study its physiological function in the whole animal model. For the adult, cdk5 is needed for proper locomotion and flight performance. Larvae lacking cdk5 in the presynaptic tissue display abnormal crawling motion, and their neuromuscular junctions (NMJ) are elongated and contain a higher number of boutons that are smaller. As a result of these two counteracting effects, the total synaptic area/NMJ is similar to wild type, leading to normal synaptic transmission, indicating that a compensatory mechanism is capable of correcting the problem caused by the lack of cdk5. futsch, the Drosophila MAP1B homolog, is also involved in NMJ morphogenesis, and analysis of the NMJ phenotype of the double mutant futsch(K68); cdk5(-) indicates that cdk5 is epistatic to futsch in this process.
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Affiliation(s)
- Alexander E Kissler
- University of Bern, Institute of Cell Biology, Baltzerstrasse 4, CH-3012 Bern, Switzerland
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163
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Hawasli AH, Koovakkattu D, Hayashi K, Anderson AE, Powell CM, Sinton CM, Bibb JA, Cooper DC. Regulation of hippocampal and behavioral excitability by cyclin-dependent kinase 5. PLoS One 2009; 4:e5808. [PMID: 19529798 PMCID: PMC2695674 DOI: 10.1371/journal.pone.0005808] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Accepted: 05/07/2009] [Indexed: 01/19/2023] Open
Abstract
Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase that has been implicated in learning, synaptic plasticity, neurotransmission, and numerous neurological disorders. We previously showed that conditional loss of Cdk5 in adult mice enhanced hippocampal learning and plasticity via modulation of calpain-mediated N-methyl-D-aspartic acid receptor (NMDAR) degradation. In the present study, we characterize the enhanced synaptic plasticity and examine the effects of long-term Cdk5 loss on hippocampal excitability in adult mice. Field excitatory post-synaptic potentials (fEPSPs) from the Schaffer collateral CA1 subregion of the hippocampus (SC/CA1) reveal that loss of Cdk5 altered theta burst topography and enhanced post-tetanic potentiation. Since Cdk5 governs NMDAR NR2B subunit levels, we investigated the effects of long-term Cdk5 knockout on hippocampal neuronal excitability by measuring NMDAR-mediated fEPSP magnitudes and population-spike thresholds. Long-term loss of Cdk5 led to increased Mg(2+)-sensitive potentials and a lower threshold for epileptiform activity and seizures. Biochemical analyses were performed to better understand the role of Cdk5 in seizures. Induced-seizures in wild-type animals led to elevated amounts of p25, the Cdk5-activating cofactor. Long-term, but not acute, loss of Cdk5 led to decreased p25 levels, suggesting that Cdk5/p25 may be activated as a homeostatic mechanism to attenuate epileptiform activity. These findings indicate that Cdk5 regulates synaptic plasticity, controls neuronal and behavioral stimulus-induced excitability and may be a novel pharmacological target for cognitive and anticonvulsant therapies.
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Affiliation(s)
- Ammar H. Hawasli
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Della Koovakkattu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Kanehiro Hayashi
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Anne E. Anderson
- Departments of Pediatrics, Neurology and Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| | - Craig M. Powell
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Christopher M. Sinton
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - James A. Bibb
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Donald C. Cooper
- Department of Psychology and Neuroscience, Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado, United States of America
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164
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Engmann O, Giese KP. Crosstalk between Cdk5 and GSK3beta: Implications for Alzheimer's Disease. Front Mol Neurosci 2009; 2:2. [PMID: 19521544 PMCID: PMC2694676 DOI: 10.3389/neuro.02.002.2009] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 05/11/2009] [Indexed: 11/13/2022] Open
Abstract
GSK3beta and Cdk5 are the two kinases in the center of research on Alzheimer's disease (AD), involved in the pathological symptoms of AD, Abeta plaque formation, tau hyperphosphorylation and neurodegeneration. So far, both kinases have mostly been examined in isolation, leading to a schism of the research field into defenders of the GSK3beta-versus the Cdk5 hypotheses of AD. However, in this debate the fact that activities of GSK3beta and Cdk5 can influence each other deserves more attention. Recent evidence from p25 transgenic mice suggests that there is a dynamic crosstalk: during aging or prolonged overactivation of Cdk5, GSK3beta activity may alter in favor of AD pathogenesis. In this review we summarize the connections between GSK3beta and Cdk5 and discuss implications for AD hypotheses.
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Affiliation(s)
- Olivia Engmann
- Institute of Psychiatry, King's College LondonLondon, UK
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165
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Orlando LR, Ayala R, Kett LR, Curley AA, Duffner J, Bragg DC, Tsai LH, Dunah AW, Young AB. Phosphorylation of the homer-binding domain of group I metabotropic glutamate receptors by cyclin-dependent kinase 5. J Neurochem 2009; 110:557-69. [PMID: 19457112 DOI: 10.1111/j.1471-4159.2009.06139.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Phosphorylation of neurotransmitter receptors can modify their activity and regulate neuronal excitability. Cyclin-dependent kinase 5 (cdk5) is a proline-directed serine/threonine kinase involved not only in neuronal development, but also in synaptic function and plasticity. Here we demonstrate that group I metabotropic glutamate receptors (mGluRs), which modulate post-synaptic signaling by coupling to intracellular signal transduction pathways, are phosphorylated by cdk5. In vitro kinase assays reveal that cdk5 phosphorylates mGluR5 within the domain of the receptor that interacts with the scaffolding protein homer. Using a novel phosphospecific mGluR antibody, we show that the homer-binding domain of both mGluR1 and mGluR5 are phosphorylated in vivo, and that inhibition of cdk5 with siRNA decreases the amount of phosphorylated receptor. Furthermore, kinetic binding analysis, by surface plasmon resonance, indicates that phosphorylation of mGluR5 enhances its association with homer. Homer protein complexes in the post-synaptic density, and their disruption by an activity-dependent short homer 1a isoform, have been shown to regulate the trafficking and signaling of the mGluRs and impact many neuroadaptive processes. Phosphorylation of the mGluR homer-binding domain, in contrast to homer 1a induction, provides a novel mechanism for potentially regulating a subset of homer interactions.
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Affiliation(s)
- Lianna R Orlando
- Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Boston, 02129, USA
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166
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Spatial learning impairment, enhanced CDK5/p35 activity, and downregulation of NMDA receptor expression in transgenic mice expressing tau-tubulin kinase 1. J Neurosci 2009; 28:14511-21. [PMID: 19118186 DOI: 10.1523/jneurosci.3417-08.2008] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Tau-tubulin kinase-1 (TTBK1) is involved in phosphorylation of tau protein at specific Serine/Threonine residues found in paired helical filaments, suggesting its role in tauopathy pathogenesis. We found that TTBK1 levels were upregulated in brains of human Alzheimer' disease (AD) patients compared with age-matched non-AD controls. To understand the effects of TTBK1 activation in vivo, we developed transgenic mice harboring human full-length TTBK1 genomic DNA (TTBK1-Tg). Transgenic TTBK1 is highly expressed in subiculum and cortical pyramidal layers, and induces phosphorylated neurofilament aggregation. TTBK1-Tg mice show significant age-dependent memory impairment as determined by radial arm water maze test, which is associated with enhancement of tau and neurofilament phosphorylation, increased levels of p25 and p35, both activators of cyclin-dependent protein kinase 5 (CDK5), enhanced calpain I activity, and reduced levels of hippocampal NMDA receptor types 2B (NR2B) and D. Enhanced CDK5/p35 complex formation is strongly correlated with dissociation of F-actin from p35, suggesting the inhibitory mechanism of CDK5/p35 complex formation by F-actin. Expression of recombinant TTBK1 in primary mouse cortical neurons significantly downregulated NR2B in a CDK5- and calpain-dependent manner. These data suggest that TTBK1 in AD brain may be one of the underlying mechanisms inducing CDK5 and calpain activation, NR2B downregulation, and subsequent memory dysfunction.
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167
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Abstract
p25/Cdk5 dysregulation may contribute to neurodegeneration. In this issue of Neuron, Kim et al. show that cdk5 inactivates HDAC-1, leading to cell cycle deregulation and DNA damage accumulation. This study provides further insights into the function of p25/Cdk5 in neurons and points to HDAC-1 as a target for therapeutic interventions.
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Affiliation(s)
- Burcin Ikiz
- Department of Neurology, Pathology, and Cell Biology and Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA
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168
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Abstract
Mitogen-activated Protein Kinases (MAPKs) are critical for the formation of stable long-term memories. New work shows that circadian MAPK activity cycling is important in the formation of new hippocampus-dependent memories.
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Affiliation(s)
- Tania L Roth
- Department of Neurobiology and McKnight Brain Institute, University of Alabama Birmingham, 1825 University Blvd., SHEL 1010, Birmingham, Alabama 35294-2182, USA.
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169
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Crews L, Patrick C, Achim CL, Everall IP, Masliah E. Molecular pathology of neuro-AIDS (CNS-HIV). Int J Mol Sci 2009; 10:1045-1063. [PMID: 19399237 PMCID: PMC2672018 DOI: 10.3390/ijms10031045] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Revised: 03/05/2009] [Accepted: 03/09/2009] [Indexed: 11/17/2022] Open
Abstract
The cognitive deficits in patients with HIV profoundly affect the quality of life of people living with this disease and have often been linked to the neuro-inflammatory condition known as HIV encephalitis (HIVE). With the advent of more effective anti-retroviral therapies, HIVE has shifted from a sub-acute to a chronic condition. The neurodegenerative process in patients with HIVE is characterized by synaptic and dendritic damage to pyramidal neurons, loss of calbindin-immunoreactive interneurons and myelin loss. The mechanisms leading to neurodegeneration in HIVE might involve a variety of pathways, and several lines of investigation have found that interference with signaling factors mediating neuroprotection might play an important role. These signaling pathways include, among others, the GSK3beta, CDK5, ERK, Pyk2, p38 and JNK cascades. Of these, GSK3beta has been a primary focus of many previous studies showing that in infected patients, HIV proteins and neurotoxins secreted by immune-activated cells in the brain abnormally activate this pathway, which is otherwise regulated by growth factors such as FGF. Interestingly, modulation of the GSK3beta signaling pathway by FGF1 or GSK3beta inhibitors (lithium, valproic acid) is protective against HIV neurotoxicity, and several pilot clinical trials have demonstrated cognitive improvements in HIV patients treated with GSK3beta inhibitors. In addition to the GSK3beta pathway, the CDK5 pathway has recently been implicated as a mediator of neurotoxicity in HIV, and HIV proteins might activate this pathway and subsequently disrupt the diverse processes that CDK5 regulates, including synapse formation and plasticity and neurogenesis. Taken together, the GSK3beta and CDK5 signaling pathways are important regulators of neurotoxicity in HIV, and modulation of these factors might have therapeutic potential in the treatment of patients suffering from HIVE. In this context, the subsequent sections will focus on reviewing the involvement of the GSK3beta and CDK5 pathways in neurodegeneration in HIV.
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Affiliation(s)
- Leslie Crews
- Department of Pathology, University of California, San Diego / 9500 Gilman Dr. La Jolla, CA 92093, U.S.A.; E-Mail:
| | - Christina Patrick
- Department of Neurosciences, University of California, San Diego / 9500 Gilman Dr. La Jolla, CA 92093, U.S.A.; E-Mail:
| | - Cristian L. Achim
- Department of Psychiatry, University of California, San Diego / 9500 Gilman Dr. La Jolla, CA 92093, U.S.A.; E-Mails:
(C.A.);
(I.E.)
| | - Ian P. Everall
- Department of Psychiatry, University of California, San Diego / 9500 Gilman Dr. La Jolla, CA 92093, U.S.A.; E-Mails:
(C.A.);
(I.E.)
| | - Eliezer Masliah
- Department of Pathology, University of California, San Diego / 9500 Gilman Dr. La Jolla, CA 92093, U.S.A.; E-Mail:
- Department of Neurosciences, University of California, San Diego / 9500 Gilman Dr. La Jolla, CA 92093, U.S.A.; E-Mail:
- Author to whom correspondence should be addressed; E-Mail:
; Tel. +1 (858) 534-8992; Fax: +1 (858) 534-6232
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170
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Abstract
Most molecular and cellular studies of cognitive function have focused on either normal or pathological states, but recent research with transgenic mice has started to address the mechanisms of enhanced cognition. These results point to key synaptic and nuclear signalling events that can be manipulated to facilitate the induction or increase the stability of synaptic plasticity, and therefore enhance the acquisition or retention of information. Here, we review these surprising findings and explore their implications to both mechanisms of learning and memory and to ongoing efforts to develop treatments for cognitive disorders. These findings represent the beginning of a fundamental new approach in the study of enhanced cognition.
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Affiliation(s)
- Yong-Seok Lee
- Department of Neurobiology, Brain Research Institute, University of California, Los Angeles, California 90095, USA
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171
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Stieler JT, Bullmann T, Kohl F, Barnes BM, Arendt T. PHF-like tau phosphorylation in mammalian hibernation is not associated with p25-formation. J Neural Transm (Vienna) 2009; 116:345-50. [PMID: 19184336 DOI: 10.1007/s00702-008-0181-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Accepted: 12/19/2008] [Indexed: 01/03/2023]
Abstract
In Alzheimer's disease and related disorders, hyperphosphorylation of tau is associated with an increased activity of cyclin dependent kinase 5 (cdk5). Elevated cdk5 activity is thought to be due to the formation of p25 and thereby represents a critical element in the dysregulation of tau phosphorylation under pathological conditions. However, there is still a controversy regarding the correlation of p25 generation and tau pathology. Recently, we demonstrated physiological, paired helical filament-like tau phosphorylation that reversibly occurs in hibernating mammals. Here we used this model to test whether the tau phosphorylation in hibernation is associated with the formation of p25. Analysing brain material of arctic ground squirrels and Syrian hamsters we found no evidence for a hibernation dependent generation of p25. Hence, we suppose that phosphorylation of tau does not require the formation of p25. Instead we suggest that the truncation of p35 to p25 represents a characteristic of pathological alterations and may contribute to aggregation and deposition of hyperphosphorylated tau.
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Affiliation(s)
- Jens Thorsten Stieler
- Department of Molecular and Cellular Mechanisms of Neurodegeneration, Paul Flechsig Institute of Brain Research, University of Leipzig, Jahnallee 59, 04109, Leipzig, Germany.
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172
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Jessberger S, Aigner S, Clemenson GD, Toni N, Lie DC, Karalay Ö, Overall R, Kempermann G, Gage FH. Cdk5 regulates accurate maturation of newborn granule cells in the adult hippocampus. PLoS Biol 2009; 6:e272. [PMID: 18998770 PMCID: PMC2581629 DOI: 10.1371/journal.pbio.0060272] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Accepted: 09/25/2008] [Indexed: 12/14/2022] Open
Abstract
Newborn granule cells become functionally integrated into the synaptic circuitry of the adult dentate gyrus after a morphological and electrophysiological maturation process. The molecular mechanisms by which immature neurons and the neurites extending from them find their appropriate position and target area remain largely unknown. Here we show that single-cell-specific knockdown of cyclin-dependent kinase 5 (cdk5) activity in newborn cells using a retrovirus-based strategy leads to aberrant growth of dendritic processes, which is associated with an altered migration pattern of newborn cells. Even though spine formation and maturation are reduced in cdk5-deficient cells, aberrant dendrites form ectopic synapses onto hilar neurons. These observations identify cdk5 to be critically involved in the maturation and dendrite extension of newborn neurons in the course of adult neurogenesis. The data presented here also suggest a mechanistic dissociation between accurate dendritic targeting and subsequent synapse formation.
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Affiliation(s)
- Sebastian Jessberger
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California, United States of America
- Institute of Cell Biology, Department of Biology, ETH Zurich, Zurich, Switzerland
- * To whom correspondence should be addressed. E-mail: (FHG); (SJ)
| | - Stefan Aigner
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California, United States of America
| | - Gregory D Clemenson
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California, United States of America
| | - Nicolas Toni
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California, United States of America
| | - D. Chichung Lie
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California, United States of America
- Helmholtz Zentrum München, German Research Center for Environmental Health, Munich, Germany
| | - Özlem Karalay
- Institute of Cell Biology, Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Rupert Overall
- Center for Regenerative Therapies (CRTD), Dresden, Germany
| | | | - Fred H Gage
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California, United States of America
- * To whom correspondence should be addressed. E-mail: (FHG); (SJ)
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173
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Kim D, Frank CL, Dobbin MM, Tsunemoto RK, Wu D, Peng PL, Guan JS, Lee BH, Moy LY, Giusti P, Broodie N, Mazitschek R, Delalle I, Haggarty SJ, Neve RL, Lu Y, Tsai LH. Deregulation of HDAC1 by p25/Cdk5 in neurotoxicity. Neuron 2008; 60:803-17. [PMID: 19081376 PMCID: PMC2912147 DOI: 10.1016/j.neuron.2008.10.015] [Citation(s) in RCA: 233] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Revised: 09/02/2008] [Accepted: 10/09/2008] [Indexed: 12/19/2022]
Abstract
Aberrant cell-cycle activity and DNA damage are emerging as important pathological components in various neurodegenerative conditions. However, their underlying mechanisms are poorly understood. Here, we show that deregulation of histone deacetylase 1 (HDAC1) activity by p25/Cdk5 induces aberrant cell-cycle activity and double-strand DNA breaks leading to neurotoxicity. In a transgenic model for neurodegeneration, p25/Cdk5 activity elicited cell-cycle activity and double-strand DNA breaks that preceded neuronal death. Inhibition of HDAC1 activity by p25/Cdk5 was identified as an underlying mechanism for these events, and HDAC1 gain of function provided potent protection against DNA damage and neurotoxicity in cultured neurons and an in vivo model for ischemia. Our findings outline a pathological signaling pathway illustrating the importance of maintaining HDAC1 activity in the adult neuron. This pathway constitutes a molecular link between aberrant cell-cycle activity and DNA damage and is a potential target for therapeutics against diseases and conditions involving neuronal death.
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Affiliation(s)
- Dohoon Kim
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
- Division of Medical Sciences, Harvard Medical School
| | - Christopher L. Frank
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
- Division of Medical Sciences, Harvard Medical School
| | - Matthew M. Dobbin
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
| | - Rachel K. Tsunemoto
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
| | - Di Wu
- Burnett College of Biomedical Sciences, University of Central Florida
| | - Peter L. Peng
- Burnett College of Biomedical Sciences, University of Central Florida
| | - Ji-Song Guan
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
| | - Byung-Hoon Lee
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
| | - Lily Y. Moy
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
| | - Paola Giusti
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
| | - Nisha Broodie
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
| | - Ralph Mazitschek
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard University
| | - Ivanna Delalle
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
| | - Stephen J. Haggarty
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard University
- Center for Human Genetic Research, Massachusetts General Hospital
| | - Rachael L. Neve
- Department of Psychiatry, Harvard Medical School, McLean Hospital
| | - YouMing Lu
- Burnett College of Biomedical Sciences, University of Central Florida
| | - Li-Huei Tsai
- Howard Hughes Medical Institute, Picower Insitute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard University
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174
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Mlewski EC, Krapacher FA, Ferreras S, Paglini G. Transient enhanced expression of Cdk5 activator p25 after acute and chronic d-amphetamine administration. Ann N Y Acad Sci 2008; 1139:89-102. [PMID: 18991853 DOI: 10.1196/annals.1432.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The cellular and molecular mechanisms of sensitization in the addictive process are still unclear. Recently, chronic treatment with cocaine has been shown to upregulate the expression of cyclin-dependent kinase 5 (cdk5) and its specific activator, p35, in the striatum, as a downstream target gene of DeltaFosB, and has been implicated in compensatory adaptive changes associated with psychostimulants. Cdk5 is a serine/threonine kinase and its activation is achieved through association with a regulatory subunit, either p35 or p39. P35 is cleaved by the protease calpain, which results in the generation of a truncated product termed p25, which contains all elements necessary for cdk5 activation. The cdk5/p35 complex plays an essential role in neuronal development and survival. It has also been involved in neuronal trafficking and transport and in dopaminergic transmission, indicating its role either in presynaptic and postsynaptic signaling. In this study we report that the cdk5/p35 complex participates in acute and chronic d-amphetamine (AMPH)-evoked behavioral events, and we show a surprisingly transient enhanced expression of p25 and a lasting increased expression of p35 in dorsal striatal synaptosomes after acute and chronic AMPH administration. Pak1, a substrate for cdk5, is also enriched in the synaptosomal fraction of acute AMPH-treated rats. Our data suggest that the transient upregulation of p25 may regulate the activity of cdk5 in phosphorylating particular substrates, such as Pak1, implicated in the compensatory adaptive morphophysiologic changes associated with the process of behavioral sensitization to psychostimulants.
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Affiliation(s)
- Estela Cecilia Mlewski
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET, Córdoba, Argentina
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175
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Luo W, Rodina A, Chiosis G. Heat shock protein 90: translation from cancer to Alzheimer's disease treatment? BMC Neurosci 2008; 9 Suppl 2:S7. [PMID: 19090995 PMCID: PMC2604891 DOI: 10.1186/1471-2202-9-s2-s7] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Both malignant transformation and neurodegeneration, as it occurs in Alzheimer's disease, are complex and lengthy multistep processes characterized by abnormal expression, post-translational modification, and processing of certain proteins. To maintain and allow the accumulation of these dysregulated processes, and to facilitate the step-wise evolution of the disease phenotype, cells must co-opt a compensatory regulatory mechanism. In cancer, this role has been attributed to heat shock protein 90 (Hsp90), a molecular chaperone that maintains the functional conformation of multiple proteins involved in cell-specific oncogenic processes. In this sense, at the phenotypic level, Hsp90 appears to serve as a biochemical buffer for the numerous cancer-specific lesions that are characteristic of diverse tumors. The current review proposes a similar role for Hsp90 in neurodegeneration. It will present experimentally demonstrated, but also hypothetical, roles that suggest Hsp90 can act as a regulator of pathogenic changes that lead to the neurodegenerative phenotype in Alzheimer's disease.
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Affiliation(s)
- Wenjie Luo
- Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University and Fisher Foundation for Alzheimer's Disease, New York, NY 10021, USA.
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176
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Striatal dysregulation of Cdk5 alters locomotor responses to cocaine, motor learning, and dendritic morphology. Proc Natl Acad Sci U S A 2008; 105:18561-6. [PMID: 19017804 PMCID: PMC2587606 DOI: 10.1073/pnas.0806078105] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Motor learning and neuro-adaptations to drugs of abuse rely upon neuronal signaling in the striatum. Cyclin-dependent kinase 5 (Cdk5) regulates striatal dopamine neurotransmission and behavioral responses to cocaine. Although the role for Cdk5 in neurodegeneration in the cortex and hippocampus and in hippocampal-dependent learning has been demonstrated, its dysregulation in the striatum has not been examined. Here we show that strong activation of striatal NMDA receptors produced p25, the truncated form of the Cdk5 co-activator p35. Furthermore, inducible overexpression of p25 in the striatum prevented locomotor sensitization to cocaine and attenuated motor coordination and learning. This corresponded with reduced dendritic spine density, increased neuro-inflammation, altered dopamine signaling, and shifted Cdk5 specificity with regard to physiological and aberrant substrates, but no apparent loss of striatal neurons. Thus, dysregulation of Cdk5 dramatically affects striatal-dependent brain function and may be relevant to non-neurodegenerative disorders involving dopamine neurotransmission.
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177
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Green KN, Steffan JS, Martinez-Coria H, Sun X, Schreiber SS, Thompson LM, LaFerla FM. Nicotinamide restores cognition in Alzheimer's disease transgenic mice via a mechanism involving sirtuin inhibition and selective reduction of Thr231-phosphotau. J Neurosci 2008; 28:11500-10. [PMID: 18987186 PMCID: PMC2617713 DOI: 10.1523/jneurosci.3203-08.2008] [Citation(s) in RCA: 289] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2008] [Revised: 08/27/2008] [Accepted: 09/07/2008] [Indexed: 12/29/2022] Open
Abstract
Memory loss is the signature feature of Alzheimer's disease, and therapies that prevent or delay its onset are urgently needed. Effective preventive strategies likely offer the greatest and most widespread benefits. Histone deacetylase (HDAC) inhibitors increase histone acetylation and enhance memory and synaptic plasticity. We evaluated the efficacy of nicotinamide, a competitive inhibitor of the sirtuins or class III NAD(+)-dependent HDACs in 3xTg-AD mice, and found that it restored cognitive deficits associated with pathology. Nicotinamide selectively reduces a specific phospho-species of tau (Thr231) that is associated with microtubule depolymerization, in a manner similar to inhibition of SirT1. Nicotinamide also dramatically increased acetylated alpha-tubulin, a primary substrate of SirT2, and MAP2c, both of which are linked to increased microtubule stability. Reduced phosphoThr231-tau was related to a reduction of monoubiquitin-conjugated tau, suggesting that this posttranslationally modified form of tau may be rapidly degraded. Overexpression of a Thr231-phospho-mimic tau in vitro increased clearance and decreased accumulation of tau compared with wild-type tau. These preclinical findings suggest that oral nicotinamide may represent a safe treatment for AD and other tauopathies, and that phosphorylation of tau at Thr231 may regulate tau stability.
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Affiliation(s)
| | | | | | | | - Steven S. Schreiber
- Neurology
- Anatomy and Neurobiology, University of California, Irvine, Irvine, California 92697-4545
| | - Leslie Michels Thompson
- Departments of Neurobiology and Behavior
- Psychiatry and Human Behavior
- Biological Chemistry, and
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178
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Nikolic M. Unravelling the complex role of Cdk5 in the developing cerebral cortex. FUTURE NEUROLOGY 2008. [DOI: 10.2217/14796708.3.6.729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The normal development of the mammalian CNS is entirely dependent on the coordinated behavior of its cellular components. Particular importance is attributed to the correct morphology, migration and communication of neurons. Recent years have seen the identification of many extracellular, cell surface and intracellular signaling molecules that are important for normal CNS development, consequently triggering huge progress in our understanding of the complex processes involved. A key molecule to emerge is Cdk5. To date, Cdk5 has been functionally linked with controlled neuronal morphology, migration, synaptic function, cognition, drug addiction, neuronal death and neurodegeneration. The complexity of its function has been confirmed by the ever increasing number of diverse upstream regulators, protein substrates and biological consequences of altered catalytic function. The aim of this review is to consolidate recent findings concerning the role of Cdk5 in the developing nervous system, particularly the cerebral cortex, where its importance is most clearly evidenced.
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Affiliation(s)
- Margareta Nikolic
- Department of Cellular & Molecular Neuroscience, Division of Neuroscience & Mental Health, School of Medicine, Imperial College London, Burlington Danes Building, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK
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179
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Hsiao YH, Chen PS, Yeh SH, Lin CH, Gean PW. N-acetylcysteine prevents β-amyloid toxicity by a stimulatory effect on p35/cyclin-dependent kinase 5 activity in cultured cortical neurons. J Neurosci Res 2008; 86:2685-95. [DOI: 10.1002/jnr.21710] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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180
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Bignante EA, Rodriguez Manzanares PA, Mlewski EC, Bertotto ME, Bussolino DF, Paglini G, Molina VA. Involvement of septal Cdk5 in the emergence of excessive anxiety induced by stress. Eur Neuropsychopharmacol 2008; 18:578-88. [PMID: 18406108 DOI: 10.1016/j.euroneuro.2008.02.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Revised: 02/05/2008] [Accepted: 02/21/2008] [Indexed: 12/11/2022]
Abstract
The aim of the present study was to evaluate whether the activation of Cdk5, a protein that has been suggested to participate in higher cognitive functions, is required for the onset of a sensitized anxiety-related behavior induced by stress. The exposure to restraint enhanced both Cdk5 expression in certain subareas of the septohippocampal system, principally in the lateral septum (LS) and septal Cdk5 kinase activity in rats. Behaviorally, restrained wild type mice showed a behavior indicative of enhanced anxiety in the elevated plus maze (EPM). In contrast, unstressed mice and stressed knockout mice, which lacked the p35 protein, the natural activator of Cdk5, displayed similar anxiety-like behavior in the EPM. Finally, the intra-LS infusion of olomoucine - a Cdk5 inhibitor - blocked the enhanced anxiety in the EPM induced by prior stress in rats. All these data provide evidence that septal Cdk5 is required in the emergence of a sensitized emotional process induced by stress.
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Affiliation(s)
- Elena Anahi Bignante
- Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba. Argentina
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181
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Crews L, Lentz MR, González RG, Fox HS, Masliah E. Neuronal injury in simian immunodeficiency virus and other animal models of neuroAIDS. J Neurovirol 2008; 14:327-39. [PMID: 18780234 PMCID: PMC2562423 DOI: 10.1080/13550280802132840] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The success of antiretroviral therapy has reduced the incidence of severe neurological complication resulting from human immunodeficiency virus (HIV) infection. However, increased patient survival has been associated with an increased prevalence of protracted forms of HIV encephalitis leading to moderate cognitive impairment. NeuroAIDS remains a great challenge to patients, their families, and our society. Thus development of preclinical models that will be suitable for testing promising new compounds with neurotrophic and neuroprotective capabilities is of critical importance. The simian immunodeficiency virus (SIV)-infected macaque is the premiere model to study HIV neuropathogenesis. This model was central to the seminal work of Dr. Opendra "Bill" Narayan. Similar to patients with HIV encephalitis, in the SIV model there is injury to the synaptodendritic structure of excitatory pyramidal neurons and inhibitory calbindin-immunoreactive interneurons. This article, which is part of a special issue of the Journal of NeuroVirology in honor of Dr. Bill Narayan, discusses the most important neurodegenerative features in preclinical models of neuroAIDS and their potential for treatment development.
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Affiliation(s)
- Leslie Crews
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Margaret R Lentz
- Massachusetts General Hospital, Division of Neuroradiology and the A.A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
| | - R Gilberto González
- Massachusetts General Hospital, Division of Neuroradiology and the A.A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
| | - Howard S Fox
- Department of Molecular and Integrative Neuroscience, The Scripps Research Institute, La Jolla, California, USA
| | - Eliezer Masliah
- Department of Pathology, University of California San Diego, La Jolla, California, USA
- Department of Neurosciences, University of California San Diego, La Jolla, California, USA
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182
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Sun KH, de Pablo Y, Vincent F, Johnson EO, Chavers AK, Shah K. Novel genetic tools reveal Cdk5's major role in Golgi fragmentation in Alzheimer's disease. Mol Biol Cell 2008; 19:3052-69. [PMID: 18480410 PMCID: PMC2441653 DOI: 10.1091/mbc.e07-11-1106] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2007] [Revised: 04/15/2008] [Accepted: 05/05/2008] [Indexed: 12/17/2022] Open
Abstract
Golgi fragmentation is a common feature in multiple neurodegenerative diseases; however, the precise mechanism that causes fragmentation remains obscure. A potential link between Cdk5 and Golgi fragmentation in Alzheimer's disease (AD) was investigated in this study. Because Golgi is physiologically fragmented during mitosis by Cdc2 kinase and current Cdk5-specific chemical inhibitors target Cdc2 as well, development of novel tools to modulate Cdk5 activity was essential. These enzyme modulators, created by fusing TAT sequence to Cdk5 activators and an inhibitor peptide, enable specific activation and inhibition of Cdk5 activity with high temporal control. These genetic tools revealed a major role of Cdk5 in Golgi fragmentation upon beta-amyloid and glutamate stimulation in differentiated neuronal cells and primary neurons. A crucial role of Cdk5 was further confirmed when Cdk5 activation alone resulted in robust Golgi disassembly. The underlying mechanism was unraveled using a chemical genetic screen, which yielded cis-Golgi matrix protein GM130 as a novel substrate of Cdk5. Identification of the Cdk5 phosphorylation site on GM130 suggested a mechanism by which Cdk5 may cause Golgi fragmentation upon deregulation in AD. As Cdk5 is activated in several neurodegenerative diseases where Golgi disassembly also occurs, this may be a common mechanism among multiple disorders.
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Affiliation(s)
- Kai-Hui Sun
- Department of Chemistry and Purdue Cancer Center, Purdue University, West Lafayette, IN 47907
| | - Yolanda de Pablo
- Department of Chemistry and Purdue Cancer Center, Purdue University, West Lafayette, IN 47907
| | - Fabien Vincent
- Department of Chemistry and Purdue Cancer Center, Purdue University, West Lafayette, IN 47907
| | - Emmanuel O. Johnson
- Department of Chemistry and Purdue Cancer Center, Purdue University, West Lafayette, IN 47907
| | - Angela K. Chavers
- Department of Chemistry and Purdue Cancer Center, Purdue University, West Lafayette, IN 47907
| | - Kavita Shah
- Department of Chemistry and Purdue Cancer Center, Purdue University, West Lafayette, IN 47907
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183
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Zhang J, Cicero SA, Wang L, Romito-DiGiacomo RR, Yang Y, Herrup K. Nuclear localization of Cdk5 is a key determinant in the postmitotic state of neurons. Proc Natl Acad Sci U S A 2008; 105:8772-7. [PMID: 18550843 PMCID: PMC2438417 DOI: 10.1073/pnas.0711355105] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Indexed: 01/03/2023] Open
Abstract
Cyclin-dependent kinase 5 (Cdk5) is a nontraditional Cdk that is primarily active in postmitotic neurons. Its best known substrates are cytoskeletal proteins. Less appreciated is its role in the maintenance of a postmitotic state. We show here that in cycling cells (NIH 3T3), the localization of Cdk5 changes from predominantly nuclear to cytoplasmic as cells reenter a cell cycle after serum starvation. Similarly, when beta-amyloid peptide is used to stimulate cultured primary neurons to reenter a cell cycle, they too show a loss of nuclear Cdk5. Blocking nuclear export pharmacologically abolishes cell cycle reentry in wild-type but not Cdk5(-/-) neurons, suggesting a Cdk5-specific effect. Cdk5 overexpression targeted to the nucleus of Cdk5(-/-) neurons effectively blocks the cell cycle, but cytoplasmic targeting is ineffective. Further, in both human Alzheimer's disease as well as in the R1.40 mouse Alzheimer's model and the E2f1(-/-) mouse, neurons expressing cell cycle markers consistently show reduced nuclear Cdk5. Thus, both in vivo and in vitro, neurons that reenter a cell cycle lose nuclear Cdk5. We propose that the nuclear Cdk5 plays an active role in allowing neurons to remain postmitotic as they mature and that loss of nuclear Cdk5 leads to cell cycle entry.
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Affiliation(s)
- Jie Zhang
- *Department of Cell Biology and Neuroscience, Rutgers University, 604 Allison Road, Piscataway, NJ 08854; and
| | | | - Li Wang
- *Department of Cell Biology and Neuroscience, Rutgers University, 604 Allison Road, Piscataway, NJ 08854; and
- Genetics
| | | | - Yan Yang
- Center for Translational Neuroscience, Department of Neurology, Case Western Reserve University School of Medicine, SOM E504, 10900 Euclid Avenue, Cleveland, OH 44120
| | - Karl Herrup
- *Department of Cell Biology and Neuroscience, Rutgers University, 604 Allison Road, Piscataway, NJ 08854; and
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184
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Keverne EB, Curley JP. Epigenetics, brain evolution and behaviour. Front Neuroendocrinol 2008; 29:398-412. [PMID: 18439660 DOI: 10.1016/j.yfrne.2008.03.001] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 11/30/2007] [Accepted: 03/01/2008] [Indexed: 12/14/2022]
Abstract
Molecular modifications to the structure of histone proteins and DNA (chromatin) play a significant role in regulating the transcription of genes without altering their nucleotide sequence. Certain epigenetic modifications to DNA are heritable in the form of genomic imprinting, whereby subsets of genes are silenced according to parent-of-origin. This form of gene regulation is primarily under matrilineal control and has evolved partly to co-ordinate in-utero development with maternal resource availability. Changes to epigenetic mechanisms in post-mitotic neurons may also be activated during development in response to environmental stimuli such as maternal care and social interactions. This results in long-lasting stable, or short-term dynamic, changes to the neuronal phenotype producing long-term behavioural consequences. Use of evolutionary conserved mechanisms have thus been adapted to modify the control of gene expression and embryonic growth of the brain as well as allowing for plastic changes in the post-natal brain in response to external environmental and social cues.
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Affiliation(s)
- Eric B Keverne
- Sub-Department of Animal Behaviour, University of Cambridge, Madingley, Cambridge, CB23 8AA, UK.
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185
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Dhariwala FA, Rajadhyaksha MS. An unusual member of the Cdk family: Cdk5. Cell Mol Neurobiol 2008; 28:351-69. [PMID: 18183483 PMCID: PMC11520031 DOI: 10.1007/s10571-007-9242-1] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Accepted: 11/14/2007] [Indexed: 12/23/2022]
Abstract
The proline-directed serine threonine kinase, Cdk5, is an unusual molecule that belongs to the well-known large family of proteins, cyclin-dependent kinases (Cdks). While it has significant homology with the mammalian Cdk2 and yeast cdc2, unlike the other Cdks, it has little role to play in cell cycle regulation and is activated by non-cyclin proteins, p35 and p39. It phosphorylates a spectrum of proteins, most of them associated with cell morphology and motility. A majority of known substrates of Cdk5 are cytoskeletal elements, signalling molecules or regulatory proteins. It also appears to be an important player in cell-cell communication. Highly conserved, Cdk5 is most abundant in the nervous system and is of special interest to neuroscientists as it appears to be indispensable for normal neural development and function. In normal cells, transcription and activity of Cdk5 is tightly regulated. Present essentially in post-mitotic neurons, its normal activity is obligatory for migration and differentiation of neurons in developing brain. Deregulation of Cdk5 has been implicated in Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, Huntington's disease and acute neuronal injury. Regulators of Cdk5 activity are considered as potential therapeutic molecules for degenerative diseases. This review focuses on the role of Cdk5 in neural cells as regulator of cytoskeletal elements, axonal guidance, membrane transport, synaptogenesis and cell survival in normal and pathological conditions.
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Affiliation(s)
- Fatema A. Dhariwala
- Department of Life Sciences, Sophia College, B. Desai Road, Mumbai, 400026 India
- Radiation Biology and Health Sciences Division, Bhabha Atomic Research Center, Mumbai, 400085 India
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186
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Knobloch M, Mansuy IM. Dendritic spine loss and synaptic alterations in Alzheimer's disease. Mol Neurobiol 2008; 37:73-82. [PMID: 18438727 DOI: 10.1007/s12035-008-8018-z] [Citation(s) in RCA: 219] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Accepted: 03/28/2008] [Indexed: 01/04/2023]
Abstract
Dendritic spines are tiny protrusions along dendrites, which constitute major postsynaptic sites for excitatory synaptic transmission. These spines are highly motile and can undergo remodeling even in the adult nervous system. Spine remodeling and the formation of new synapses are activity-dependent processes that provide a basis for memory formation. A loss or alteration of these structures has been described in patients with neurodegenerative disorders such as Alzheimer's disease (AD), and in mouse models for these disorders. Such alteration is thought to be responsible for cognitive deficits long before or even in the absence of neuronal loss, but the underlying mechanisms are poorly understood. This review will describe recent findings and discoveries on the loss or alteration of dendritic spines induced by the amyloid beta (Abeta) peptide in the context of AD.
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Affiliation(s)
- Marlen Knobloch
- Division of Psychiatry Research, University of Zurich, 8008 Zurich, Switzerland
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187
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Interplay between cyclin-dependent kinase 5 and glycogen synthase kinase 3 beta mediated by neuregulin signaling leads to differential effects on tau phosphorylation and amyloid precursor protein processing. J Neurosci 2008; 28:2624-32. [PMID: 18322105 DOI: 10.1523/jneurosci.5245-07.2008] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cyclin-dependent kinase 5 (cdk5) and glycogen synthase kinase 3beta (GSK3beta) have been implicated in pathogenic processes associated with Alzheimer's disease because both kinases regulate tau hyperphosphorylation and enhance amyloid precursor protein (APP) processing leading to an increase in amyloid beta (Abeta) production. Here we show that young p25 overexpressing mice have enhanced cdk5 activity but reduced GSK3beta activity attributable to phosphorylation at the inhibitory GSK3beta-serine 9 (GSK3beta-S9) site. Phosphorylation at this site was mediated by enhanced activity of the neuregulin receptor complex, ErbB, and activation of the downstream phosphatidylinositol 3 kinase/Akt pathway. Young p25 mice had elevated Abeta peptide levels, but phospho-tau levels were decreased overall. Thus, cdk5 appears to play a dominant role in the regulation of amyloidogenic APP processing, whereas GSK3beta plays a dominant role in overall tau phosphorylation. In older mice, GSK3beta inhibitory phosphorylation at S9 was reduced relative to young mice. Abeta peptide levels were still elevated but phospho-tau levels were either unchanged or showed a trend to increase, suggesting that GSK3beta activity increases with aging. Inhibition of cdk5 by a specific inhibitor reduced cdk5 activity in p25 mice, leading to reduced Abeta production in both young and old mice. However, in young mice, cdk5 inhibition reversed GSK3beta inhibition, leading to an increase in overall tau phosphorylation. When cdk5 inhibitor was administered to very old, nontransgenic mice, inhibition of cdk5 reduced Abeta levels, and phospho-tau levels showed a trend to increase. Thus, cdk5 inhibitors may not be effective in targeting tau phosphorylation in the elderly.
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188
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Cyclin-dependent kinase 5 is associated with risk for Alzheimer's disease in a Dutch population-based study. J Neurol 2008; 255:655-62. [PMID: 18350355 DOI: 10.1007/s00415-008-0770-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Revised: 10/01/2007] [Accepted: 10/08/2007] [Indexed: 10/22/2022]
Abstract
Although the role of the Cdk5 protein in Alzheimer's disease (AD) is well recognized, there have been relatively few studies investigating genetic variants in the CDK5 gene in AD. In this study, we assessed the association between five previously described single nucleotide polymorphisms (SNPs) in the CDK5 gene and late onset AD by means of logistic regression and haplotype association analyses. Including all prevalent and incident AD cases, we found a significantly increased risk of AD for carriers of the GG genotype of SNP rs2069442 (OR = 1.79, 95 % CI 1.16-2.79, p = 0.001) in those without APOE*4. When limiting the analysis to incident cases without APOE*4, carriers of the GG genotype showed a 1.9-fold increased risk of AD (95 % CI 1.16-3.10, p = 0.003). Variations in the CDK5 gene can be described in 5 haplotype blocks. In our analysis, the haplotype tagged by the G allele of SNP rs2069442 was significantly associated with AD (p = 0.05). In conclusion, our study suggests that CDK5 may be associated with AD.
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189
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Cdk5 regulates the phosphorylation of tyrosine 1472 NR2B and the surface expression of NMDA receptors. J Neurosci 2008; 28:415-24. [PMID: 18184784 DOI: 10.1523/jneurosci.1900-07.2008] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
NMDA receptors (NMDARs) are a major class of ionotropic glutamate receptors that can undergo activity-dependent changes in surface expression. Clathrin-mediated endocytosis is a mechanism by which the surface expression of NR2B-containing NMDA receptors is regulated. The C terminus of the NMDA receptor subunit NR2B contains the internalization motif YEKL, which is the binding site for the clathrin adaptor AP-2. The tyrosine (Y1472) within the YEKL motif is phosphorylated by the Src family of kinases and this phosphorylation inhibits the binding of AP-2 and promotes surface expression of NMDA receptors. Cdk5 is a serine/threonine kinase that has been implicated in synaptic plasticity, learning, and memory. Here we demonstrate that inhibition of Cdk5 results in increased phosphorylation of Y1472 NR2B at synapses and decreased binding of NR2B to beta2-adaptin, a subunit of AP-2, thus blocking the activity-dependent endocytosis of NMDA receptors. Furthermore, we show that inhibition of Cdk5 increases the binding of Src to postsynaptic density-95 (PSD-95), and that expression of PSD-95 facilitates the phosphorylation of Y1472 NR2B by Src. Together, these results suggest a model in which inhibition of Cdk5 increases the binding of Src to PSD-95 and the phosphorylation of Y1472 NR2B by Src, which results in decreased binding of NR2B to AP-2, and NR2B/NMDAR endocytosis. This study provides a novel molecular mechanism for the regulation of the surface expression of NR2B-containing NMDA receptors and gives insight into the Cdk5-dependent regulation of synaptic plasticity.
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190
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The potential for beta-structure in the repeat domain of tau protein determines aggregation, synaptic decay, neuronal loss, and coassembly with endogenous Tau in inducible mouse models of tauopathy. J Neurosci 2008; 28:737-48. [PMID: 18199773 DOI: 10.1523/jneurosci.2824-07.2008] [Citation(s) in RCA: 216] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
We describe two new transgenic mouse lines for studying pathological changes of Tau protein related to Alzheimer's disease. They are based on the regulatable expression of the four-repeat domain of human Tau carrying the FTDP17 (frontotemporal dementia and parkinsonism linked to chromosome 17) mutation deltaK280 (Tau(RD)/deltaK280), or the deltaK280 plus two proline mutations in the hexapeptide motifs (Tau(RD)/deltaK280/I277P/I308P). The deltaK280 mutation accelerates aggregation ("proaggregation mutant"), whereas the proline mutations inhibit Tau aggregation in vitro and in cell models ("antiaggregation mutant"). The inducible transgene expression was driven by the forebrain-specific CaMKIIalpha (calcium/calmodulin-dependent protein kinase IIalpha) promoter. The proaggregation mutant leads to Tau aggregates and tangles as early as 2-3 months after gene expression, even at low expression (70% of endogenous mouse Tau). The antiaggregation mutant does not aggregate even after 22 months of gene expression. Both mutants show missorting of Tau in the somatodendritic compartment and hyperphosphorylation in the repeat domain [KXGS motifs, targets of the kinase MARK (microtubule affinity regulating kinase)]. This indicates that these changes are related to Tau expression rather than aggregation. The proaggregation mutant causes astrogliosis, loss of synapses and neurons from 5 months of gene expression onward, arguing that Tau toxicity is related to aggregation. Remarkably, the human proaggregation mutant Tau(RD) coaggregates with mouse Tau, coupled with missorting and hyperphosphorylation at multiple sites. When expression of proaggregation Tau(RD) is switched off, soluble and aggregated exogenous Tau(RD) disappears within 1.5 months. However, tangles of mouse Tau, hyperphosphorylation, and missorting remain, suggesting an extended lifetime of aggregated wild-type Tau once a pathological conformation and aggregation is induced by a proaggregation Tau species.
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191
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Muyllaert D, Terwel D, Kremer A, Sennvik K, Borghgraef P, Devijver H, Dewachter I, Van Leuven F. Neurodegeneration and neuroinflammation in cdk5/p25-inducible mice: a model for hippocampal sclerosis and neocortical degeneration. THE AMERICAN JOURNAL OF PATHOLOGY 2008; 172:470-85. [PMID: 18202185 DOI: 10.2353/ajpath.2008.070693] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The cyclin-dependent kinase cdk5 is atypically active in postmitotic neurons and enigmatic among the kinases proposed as molecular actors in neurodegeneration. We generated transgenic mice to express p25, the N-terminally truncated p35 activator of cdk5, in forebrain under tetracycline control (TET-off). Neuronal expression of p25 (p25(ON)) caused high mortality postnatally and early in life. Mortality was completely prevented by administration of doxycycline in the drinking water of pregnant dams and litters until P42, allowing us to study the action of p25 in adult mouse forebrain. Neuronal p25 triggered neurodegeneration and also microgliosis, rapidly and intensely in hippocampus and cortex. Progressive neurodegeneration was severe with marked neuron loss, causing brain atrophy (40% loss at age 5 months) with nearly complete elimination of the hippocampus. Neurodegeneration did not involve phosphorylation of protein tau or generation of amyloid peptide. Degenerating neurons did not stain for terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling or activated caspase-3 but were marked by FluoroJadeB in early stages. Diseased neurons were always closely associated with activated microglia already very early in the disease process. Primary neurons derived from p25 embryos were more prone to apoptosis than wild-type neurons, and they activated microglial cells in co-culture. The inducible p25 mice present as a model for neurodegeneration in hippocampal sclerosis and neocortical degeneration, with important contributions of activated microglia.
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Affiliation(s)
- David Muyllaert
- Department of Human Genetics, KULeuven-Campus Gasthuisberg ON1-06.602, B-3000 Leuven, Belgium
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192
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Abstract
Cyclin-dependent kinase 5 (Cdk5) regulates dopamine neurotransmission and has been suggested to serve as a homeostatic target of chronic psychostimulant exposure. To study the role of Cdk5 in the modulation of the cellular and behavioral effects of psychoactive drugs of abuse, we developed Cre/loxP conditional knock-out systems that allow temporal and spatial control of Cdk5 expression in the adult brain. Here, we report the generation of Cdk5 conditional knock-out (cKO) mice using the alphaCaMKII promoter-driven Cre transgenic line (CaMKII-Cre). In this model system, loss of Cdk5 in the adult forebrain increased the psychomotor-activating effects of cocaine. Additionally, these CaMKII-Cre Cdk5 cKO mice show enhanced incentive motivation for food as assessed by instrumental responding on a progressive ratio schedule of reinforcement. Behavioral changes were accompanied by increased excitability of medium spiny neurons in the nucleus accumbens (NAc) in Cdk5 cKO mice. To study NAc-specific effects of Cdk5, another model system was used in which recombinant adeno-associated viruses expressing Cre recombinase caused restricted loss of Cdk5 in NAc neurons. Targeted knock-out of Cdk5 in the NAc facilitated cocaine-induced locomotor sensitization and conditioned place preference for cocaine. These results suggest that Cdk5 acts as a negative regulator of neuronal excitability in the NAc and that Cdk5 may govern the behavioral effects of cocaine and motivation for reinforcement.
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193
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Samuels BA, Hsueh YP, Shu T, Liang H, Tseng HC, Hong CJ, Su SC, Volker J, Neve RL, Yue DT, Tsai LH. Cdk5 promotes synaptogenesis by regulating the subcellular distribution of the MAGUK family member CASK. Neuron 2007; 56:823-37. [PMID: 18054859 PMCID: PMC2151975 DOI: 10.1016/j.neuron.2007.09.035] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 06/08/2007] [Accepted: 09/26/2007] [Indexed: 10/22/2022]
Abstract
Synaptogenesis is a highly regulated process that underlies formation of neural circuitry. Considerable work has demonstrated the capability of some adhesion molecules, such as SynCAM and Neurexins/Neuroligins, to induce synapse formation in vitro. Furthermore, Cdk5 gain of function results in an increased number of synapses in vivo. To gain a better understanding of how Cdk5 might promote synaptogenesis, we investigated potential crosstalk between Cdk5 and the cascade of events mediated by synapse-inducing proteins. One protein recruited to developing terminals by SynCAM and Neurexins/Neuroligins is the MAGUK family member CASK. We found that Cdk5 phosphorylates and regulates CASK distribution to membranes. In the absence of Cdk5-dependent phosphorylation, CASK is not recruited to developing synapses and thus fails to interact with essential presynaptic components. Functional consequences include alterations in calcium influx. Mechanistically, Cdk5 regulates the interaction between CASK and liprin-alpha. These results provide a molecular explanation of how Cdk5 can promote synaptogenesis.
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Affiliation(s)
- Benjamin Adam Samuels
- Howard Hughes Medical Institute, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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194
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Juo P, Harbaugh T, Garriga G, Kaplan JM. CDK-5 regulates the abundance of GLR-1 glutamate receptors in the ventral cord of Caenorhabditis elegans. Mol Biol Cell 2007; 18:3883-93. [PMID: 17671168 PMCID: PMC1995742 DOI: 10.1091/mbc.e06-09-0818] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Revised: 06/21/2007] [Accepted: 07/20/2007] [Indexed: 11/11/2022] Open
Abstract
The proline-directed kinase Cdk5 plays a role in several aspects of neuronal development. Here, we show that CDK-5 activity regulates the abundance of the glutamate receptor GLR-1 in the ventral cord of Caenorhabditis elegans and that it produces corresponding changes in GLR-1-dependent behaviors. Loss of CDK-5 activity results in decreased abundance of GLR-1 in the ventral cord, accompanied by accumulation of GLR-1 in neuronal cell bodies. Genetic analysis of cdk-5 and the clathrin adaptin unc-11 AP180 suggests that CDK-5 functions prior to endocytosis at the synapse. The scaffolding protein LIN-10/Mint-1 also regulates GLR-1 abundance in the nerve cord. CDK-5 phosphorylates LIN-10/Mint-1 in vitro and bidirectionally regulates the abundance of LIN-10/Mint-1 in the ventral cord. We propose that CDK-5 promotes the anterograde trafficking of GLR-1 and that phosphorylation of LIN-10 may play a role in this process.
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Affiliation(s)
- Peter Juo
- Department of Molecular Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston, MA 02114, USA.
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195
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Muresan Z, Muresan V. The amyloid-beta precursor protein is phosphorylated via distinct pathways during differentiation, mitosis, stress, and degeneration. Mol Biol Cell 2007; 18:3835-44. [PMID: 17634293 PMCID: PMC1995701 DOI: 10.1091/mbc.e06-07-0625] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Accepted: 07/09/2007] [Indexed: 12/12/2022] Open
Abstract
Phosphorylation of amyloid-beta precursor protein (APP) at Thr(668) is a normal process linked to neurite extension and anterograde transport of vesicular cargo. By contrast, increased phosphorylation of APP is a pathological trait of Alzheimer's disease. APP is overexpressed in Down's syndrome, a condition that occasionally leads to increased APP phosphorylation, in cultured cells. Whether phosphorylation of APP in normal versus high APP conditions occurs by similar or distinct signaling pathways is not known. Here, we addressed this problem using brainstem-derived neurons (CAD cells). CAD cells that ectopically overexpress APP frequently show features of degenerating neurons. We found that, in degenerating cells, APP is hyperphosphorylated and colocalizes with early endosomes. By contrast, in normal CAD cells, phosphorylated APP (pAPP) is excluded from endosomes, and localizes to the Golgi apparatus and to transport vesicles within the neurites. Whereas the neuritic APP is phosphorylated by c-Jun NH(2)-terminal kinase through a pathway that is modulated by glycogen synthase kinase 3beta, the endosomal pAPP in degenerated CAD cells results from activation of cyclin-dependent kinase 5. Additional signaling pathways, leading to APP phosphorylation, become active during stress and mitosis. We conclude that distinct pathways of APP phosphorylation operate in proliferating, differentiating, stressed, and degenerating neurons.
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Affiliation(s)
- Zoia Muresan
- Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ 07103
| | - Virgil Muresan
- Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ 07103
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196
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Abstract
Since the isolation of cyclin-dependent kinase 5 (Cdk5), this proline-directed serine/threonine kinase has been demonstrated as an important regulator of neuronal migration, neuronal survival and synaptic functions. Recently, a number of players implicated in dendrite and synapse development have been identified as Cdk5 substrates. Neurite extension, synapse and spine maturation are all modulated by a myriad of extracellular guidance cues or trophic factors. Cdk5 was recently demonstrated to regulate signaling downstream of some of these extracellular factors, in addition to modulating Rho GTPase activity, which regulates cytoskeletal dynamics. In this communication, we summarize our existing knowledge on the pathways and mechanisms through which Cdk5 affects dendrite, synapse and spine development.
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Affiliation(s)
- Zelda H Cheung
- Department of Biochemistry, Biotechnology Research Institute and Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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197
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Abstract
Protein kinases mediate the intracellular signal transduction pathways controlling synaptic plasticity in the central nervous system. While the majority of protein kinases achieve this function via the phosphorylation of synaptic substrates, some kinases may contribute through alternative mechanisms in addition to enzymatic activity. There is growing evidence that protein kinases may often play structural roles in plasticity as well. Cyclin-dependent kinase 5 (Cdk5) has been implicated in learning and synaptic plasticity. Initial scrutiny focused on its enzymatic activity using pharmacological inhibitors and genetic modifications of Cdk5 cofactors. Quite recently Cdk5 has been shown to govern learning and plasticity via regulation of glutamate receptor degradation, a function that may not dependent on phosphorylation of downstream effectors. From these new studies, two roles emerge for Cdk5 in plasticity: one in which it controls structural plasticity via phosphorylation of synaptic substrates, and a second where it regulates functional plasticity via protein-protein interactions.
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Affiliation(s)
- Ammar H Hawasli
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9070, USA
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198
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Chen F, Qian L, Yang ZH, Huang Y, Ngo ST, Ruan NJ, Wang J, Schneider C, Noakes PG, Ding YQ, Mei L, Luo ZG. Rapsyn interaction with calpain stabilizes AChR clusters at the neuromuscular junction. Neuron 2007; 55:247-60. [PMID: 17640526 DOI: 10.1016/j.neuron.2007.06.031] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Revised: 03/27/2007] [Accepted: 06/25/2007] [Indexed: 12/28/2022]
Abstract
Agrin induces, whereas acetylcholine (ACh) disperses, ACh receptor (AChR) clusters during neuromuscular synaptogenesis. Such counteractive interaction leads to eventual dispersal of nonsynaptic AChR-rich sites and formation of receptor clusters at the postjunctional membrane. However, the underlying mechanisms are not well understood. Here we show that calpain, a calcium-dependent protease, is activated by the cholinergic stimulation and is required for induced dispersion of AChR clusters. Interestingly, the AChR-associated protein rapsyn interacted with calpain in an agrin-dependent manner, and this interaction inhibited the protease activity of calpain. Disrupting the endogenous rapsyn/calpain interaction enhanced CCh-induced dispersion of AChR clusters. Moreover, the loss of AChR clusters in agrin mutant mice was partially rescued by the inhibition of calpain via overexpressing calpastatin, an endogenous calpain inhibitor, or injecting calpeptin, a cell-permeable calpain inhibitor. These results demonstrate that calpain participates in ACh-induced dispersion of AChR clusters, and rapsyn stabilizes AChR clusters by suppressing calpain activity.
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Affiliation(s)
- Fei Chen
- Institute of Neuroscience and Key Laboratory of Neurobiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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199
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Sen A, Thom M, Martinian L, Harding B, Cross JH, Nikolic M, Sisodiya SM. Pathological tau tangles localize to focal cortical dysplasia in older patients. Epilepsia 2007; 48:1447-54. [PMID: 17441989 DOI: 10.1111/j.1528-1167.2007.01107.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Reactivation of neurodevelopmental processes may contribute to neurodegeneration. For example, the proteins cyclin dependent kinase 5 (cdk5) and glycogen synthase kinase 3 beta (GSK3beta), which are essential to normal cortical development, can hyperphosphorylate tau and might contribute to the pathogenesis of Alzheimer's disease. Focal cortical dysplasia (FCD) is an important neurodevelopmental cause of refractory human epilepsy within which dysplastic neurons exhibit increased immunoreactivity for cdk5 and GSK3beta as well as neurofilamentous accumulations. We therefore hypothesized that the developmentally abnormal cortex of FCD might be more susceptible to tau-mediated neurodegeneration than adjacent histologically normal cortex. MATERIALS AND METHODS We examined a series of 15 cases of FCD, spanning a wide age range, for beta-amyloid, pathologically phosphorylated tau and neurofibrillary tangles using silver staining, immunohistochemistry for tau, AT8, RD3, RD4 and two-dimensional cell counting. RESULTS Beta-amyloid plaques, aberrantly phosphorylated tau and neurofibrillary tangles are only found in older patients. The hyperphosphorylated tau tangles are confined to dysplastic neurons. Immunoreactivity for 3- and 4-repeat tau was again only detected within regions of FCD in older patients. With increasing age, the dysplastic cortex became hypocellular and a higher proportion of dysplastic neurons exhibited pathological tau phosphorylation. CONCLUSIONS In older patients, FCD appears more susceptible to formation of pathologically phosphorylated tau neurofibrillary tangles than adjacent histologically normal cortex. Our results suggest a novel convergence of pathological neurodevelopment with pathological age-related neurodegeneration.
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Affiliation(s)
- Arjune Sen
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, Queen Square, London, UK
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Sananbenesi F, Fischer A, Wang X, Schrick C, Neve R, Radulovic J, Tsai LH. A hippocampal Cdk5 pathway regulates extinction of contextual fear. Nat Neurosci 2007; 10:1012-9. [PMID: 17632506 PMCID: PMC2441763 DOI: 10.1038/nn1943] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2007] [Accepted: 06/26/2007] [Indexed: 12/17/2022]
Abstract
Treatment of emotional disorders involves the promotion of extinction processes, which are defined as the learned reduction of fear. The molecular mechanisms underlying extinction have only begun to be elucidated. By employing genetic and pharmacological approaches in mice, we show here that extinction requires downregulation of Rac-1 and cyclin-dependent kinase 5 (Cdk5), and upregulation of p21 activated kinase-1 (PAK-1) activity. This is physiologically achieved by a Rac-1-dependent relocation of the Cdk5 activator p35 from the membrane to the cytosol and dissociation of p35 from PAK-1. Moreover, our data suggest that Cdk5/p35 activity prevents extinction in part by inhibition of PAK-1 activity in a Rac-1-dependent manner. We propose that extinction of contextual fear is regulated by counteracting components of a molecular pathway involving Rac-1, Cdk5 and PAK-1. Our data suggest that this pathway could provide a suitable target for therapeutic treatment of emotional disorders.
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Affiliation(s)
- Farahnaz Sananbenesi
- Howard Hughes Medical Institute, Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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