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Gonda S, Köhler I, Haase A, Czubay K, Räk A, Riedel C, Wahle P. Optogenetic stimulation shapes dendritic trees of infragranular cortical pyramidal cells. Front Cell Neurosci 2023; 17:1212483. [PMID: 37587917 PMCID: PMC10427221 DOI: 10.3389/fncel.2023.1212483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 06/09/2023] [Indexed: 08/18/2023] Open
Abstract
Spontaneous or experimentally evoked activity can lead to changes in length and/or branching of neocortical pyramidal cell dendrites. For instance, an early postnatal overexpression of certain AMPA or kainate glutamate receptor subunits leads to larger amplitudes of depolarizing events driven by spontaneous activity, and this increases apical dendritic complexity. Whether stimulation frequency has a role is less clear. In this study, we report that the expression of channelrhodopsin2-eYFP was followed by a 5-day optogenetic stimulation from DIV 5-10 or 11-15 in organotypic cultures of rat visual cortex-evoked dendritic remodeling. Stimulation at 0.05 Hz, at a frequency range of spontaneous calcium oscillations known to occur in the early postnatal neocortex in vivo until eye opening, had no effect. Stimulation with 0.5 Hz, a frequency at which the cortex in vivo adopts after eye opening, unexpectedly caused shorter and somewhat less branched apical dendrites of infragranular pyramidal neurons. The outcome resembles the remodeling of corticothalamic and callosal projection neurons of layers VI and V, which in the adult have apical dendrites no longer terminating in layer I. Exposure to 2.5 Hz, a frequency not occurring naturally during the time windows, evoked dendritic damage. The results suggested that optogenetic stimulation at a biologically meaningful frequency for the selected developmental stage can influence dendrite growth, but contrary to expectation, the optogenetic stimulation decreased dendritic growth.
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Choi S, Kang D, Kang J, Hong DK, Kang BS, Kho AR, Choi BY, Huh SO, Suh SW. The Role of Zinc in Axon Formation via the mTORC1 Pathway. Mol Neurobiol 2022; 59:3206-3217. [PMID: 35293604 DOI: 10.1007/s12035-022-02785-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 02/15/2022] [Indexed: 10/18/2022]
Abstract
Zinc is an essential micronutrient required for proper function during neuronal development because it can modulate neuronal function and structure. A fully functional description of zinc in axonal processing in the central nervous system remains elusive. Here, we define the role of intracellular zinc in axon formation and elongation, involving the mammalian target of rapamycin complex 1 (mTORC1). To investigate the involvement of zinc in axon growth, we performed an ex vivo culture of mouse hippocampal neurons and administrated ZnCl2 as a media supplement. At 2 days in vitro, the administration of zinc induced the formation of multiple and elongated axons in the ex vivo culture system. A similar outcome was witnessed in callosal projection neurons in a developing mouse brain. Treatment with extracellular zinc activated the mTORC1 signaling pathway in mouse hippocampal neuronal cultures. The zinc-dependent enhancement of neuronal processing was inhibited either by the deactivation of mTORC1 with RAPTOR shRNA or by mTOR-insensitive 4EBP1 mutants. Additionally, zinc-dependent mTORC1 activation enhanced the axonal translation of TC10 and Par3 may be responsible for axonal growth. We identified a promising role of zinc in controlling axonogenesis in the developing brain, which, in turn, may indicate a novel structural role of zinc in the cytoskeleton and developing neurons.
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Affiliation(s)
- Seunghyuk Choi
- Department of Physiology, College of Medicine, Hallym University, Hallymdaehak-gil 1, Chuncheon, 24252, Republic of Korea
| | - Donghyeon Kang
- Department of Physiology, College of Medicine, Hallym University, Hallymdaehak-gil 1, Chuncheon, 24252, Republic of Korea
| | - Jieun Kang
- Department of Pharmacology, College of Medicine, Hallym University, Hallymdaehak-gil 1, Chuncheon, 24252, Republic of Korea
| | - Dae Ki Hong
- Department of Physiology, College of Medicine, Hallym University, Hallymdaehak-gil 1, Chuncheon, 24252, Republic of Korea
| | - Beom Seok Kang
- Department of Physiology, College of Medicine, Hallym University, Hallymdaehak-gil 1, Chuncheon, 24252, Republic of Korea
| | - A Ra Kho
- Department of Physiology, College of Medicine, Hallym University, Hallymdaehak-gil 1, Chuncheon, 24252, Republic of Korea
| | - Bo Young Choi
- Department of Physiology, College of Medicine, Hallym University, Hallymdaehak-gil 1, Chuncheon, 24252, Republic of Korea
| | - Sung-Oh Huh
- Department of Pharmacology, College of Medicine, Hallym University, Hallymdaehak-gil 1, Chuncheon, 24252, Republic of Korea
| | - Sang Won Suh
- Department of Physiology, College of Medicine, Hallym University, Hallymdaehak-gil 1, Chuncheon, 24252, Republic of Korea.
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Estes S, Zhong L, Artinian L, Rehder V. Regulation of electrical activity and neuronal excitability in Helisoma trivolvis by carbon monoxide. Neuroscience 2015; 311:453-63. [DOI: 10.1016/j.neuroscience.2015.10.056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 10/23/2015] [Accepted: 10/28/2015] [Indexed: 11/30/2022]
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Estes S, Zhong LR, Artinian L, Tornieri K, Rehder V. The role of action potentials in determining neuron-type-specific responses to nitric oxide. Dev Neurobiol 2014; 75:435-51. [DOI: 10.1002/dneu.22233] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 09/22/2014] [Indexed: 12/14/2022]
Affiliation(s)
- Stephen Estes
- Department of Biology; Georgia State University; Atlanta Georgia 30302
| | - Lei Ray Zhong
- Department of Biology; Georgia State University; Atlanta Georgia 30302
| | - Liana Artinian
- Department of Biology; Georgia State University; Atlanta Georgia 30302
| | - Karine Tornieri
- Department of Biology; Georgia State University; Atlanta Georgia 30302
| | - Vincent Rehder
- Department of Biology; Georgia State University; Atlanta Georgia 30302
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Zhong LR, Estes S, Artinian L, Rehder V. Acetylcholine elongates neuronal growth cone filopodia via activation of nicotinic acetylcholine receptors. Dev Neurobiol 2013; 73:487-501. [PMID: 23335470 DOI: 10.1002/dneu.22071] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 01/02/2013] [Accepted: 01/04/2013] [Indexed: 11/10/2022]
Abstract
In addition to acting as a classical neurotransmitter in synaptic transmission, acetylcholine (ACh) has been shown to play a role in axonal growth and growth cone guidance. What is not well understood is how ACh acts on growth cones to affect growth cone filopodia, structures known to be important for neuronal pathfinding. We addressed this question using an identified neuron (B5) from the buccal ganglion of the pond snail Helisoma trivolvis in cell culture. ACh treatment caused pronounced filopodial elongation within minutes, an effect that required calcium influx and resulted in the elevation of the intracellular calcium concentration ([Ca]i ). Whole-cell patch clamp recordings showed that ACh caused a reduction in input resistance, a depolarization of the membrane potential, and an increase in firing frequency in B5 neurons. These effects were mediated via the activation of nicotinic acetylcholine receptors (nAChRs), as the nAChR agonist dimethylphenylpiperazinium (DMPP) mimicked the effects of ACh on filopodial elongation, [Ca]i elevation, and changes in electrical activity. Moreover, the nAChR antagonist tubucurarine blocked all DMPP-induced effects. Lastly, ACh acted locally at the growth cone, because growth cones that were physically isolated from their parent neuron responded to ACh by filopodial elongation with a similar time course as growth cones that remained connected to their parent neuron. Our data revealed a critical role for ACh as a modulator of growth cone filopodial dynamics. ACh signaling was mediated via nAChRs and resulted in Ca influx, which, in turn, caused filopodial elongation.
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Affiliation(s)
- Lei Ray Zhong
- Biology Department, Georgia State University, Atlanta, GA 30302, USA
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Licursi V, Caiello I, Lombardi L, De Stefano ME, Negri R, Paggi P. Lack of dystrophin in mdx mice modulates the expression of genes involved in neuron survival and differentiation. Eur J Neurosci 2012; 35:691-701. [DOI: 10.1111/j.1460-9568.2011.07984.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
High content analysis of neurite outgrowth enables the rapid and comprehensive phenotypic assessment of individual neurons in a multiwell format amenable to high throughput assays. The resulting data are considered "high content" because multiple measurements of neuronal outgrowth and morphometric data are calculated from hundreds of individual cells within each image. This approach has been widely adopted by the pharmaceutical industry to accelerate neurological drug discovery and in vitro safety assessment. High content technology utilizes automated fluorescent and/or brightfield microscopy for image acquisition. The acquired images are then quantified using mathematical algorithms to measure pertinent neurobiological morphometric information, including neurite length, count, and extent of branching for each cell within the images. Furthermore, evaluation of the individual cell-level measurements enables the detection of subpopulations of cellular responders not apparent when examining well-level averages. Using this technology, neurite outgrowth can be quantified in each well, derived from hundreds of cell measurements in a 96-well microplate in approximately 30 min.
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GAFAROV F, KHUSNUTDINOV N, GALIMYANOV F. MORPHOLESS NEURONS COMPROMISE THE DEVELOPMENT OF CORTICAL CONNECTIVITY. J Integr Neurosci 2009; 8:35-48. [DOI: 10.1142/s0219635209002058] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Revised: 02/05/2009] [Indexed: 01/16/2023] Open
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Radio NM, Mundy WR. Developmental neurotoxicity testing in vitro: models for assessing chemical effects on neurite outgrowth. Neurotoxicology 2008; 29:361-76. [PMID: 18403021 DOI: 10.1016/j.neuro.2008.02.011] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 02/13/2008] [Accepted: 02/20/2008] [Indexed: 11/15/2022]
Abstract
In vitro models may be useful for the rapid toxicological screening of large numbers of chemicals for their potential to produce toxicity. Such screening could facilitate prioritization of resources needed for in vivo toxicity testing towards those chemicals most likely to result in adverse health effects. Cell cultures derived from nervous system tissue have proven to be powerful tools for elucidating cellular and molecular mechanisms of nervous system development and function, and have been used to understand the mechanism of action of neurotoxic chemicals. Recently, it has been suggested that in vitro models could be used to screen for chemical effects on critical cellular events of neurodevelopment, including differentiation and neurite growth. This review examines the use of neuronal cell cultures as an in vitro model of neurite outgrowth. Examples of the cell culture systems that are commonly used to examine the effects of chemicals on neurite outgrowth are provided, along with a description of the methods used to quantify this neurodevelopmental process in vitro. Issues relating to the relevance of the methods and models currently used to assess neurite outgrowth are discussed in the context of hazard identification and chemical screening. To demonstrate the utility of in vitro models of neurite outgrowth for the evaluation of large numbers of chemicals, efforts should be made to: (1) develop a set of reference chemicals that can be used as positive and negative controls for comparing neurite outgrowth between model systems, (2) focus on cell cultures of human origin, with emphasis on the emerging area of neural progenitor cells, and (3) use high-throughput methods to quantify endpoints of neurite outgrowth.
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Affiliation(s)
- Nicholas M Radio
- Neurotoxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protections Agency (USEPA), B105-06 Research Triangle Park, NC 27711, USA
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Marée AFM, Jilkine A, Dawes A, Grieneisen VA, Edelstein-Keshet L. Polarization and Movement of Keratocytes: A Multiscale Modelling Approach. Bull Math Biol 2006; 68:1169-211. [PMID: 16794915 DOI: 10.1007/s11538-006-9131-7] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 03/31/2006] [Indexed: 02/05/2023]
Abstract
Eukariotic cell motility is a complex phenomenon, in which the cytoskeleton and its major constituent, actin, play an essential role. Actin forms polymers of long, stiff filaments that are cross-linked into an anisotropic network inside a thin sheet-like cellular protrusion, the lamellipod. At the leading edge of this structure, polymerization of actin filaments creates the force that pushes out the membrane and leads to translocation of a motile cell. Dynamics of the actin network account for changes in cell shape, crawling motion and turning of the cell in response to external cues. Regulating the dynamics of the cytoskeleton, and playing a central role in signal transduction in the cell, are Cdc42, Rac and Rho (GTPases of the rho family, collectively known as the small G-proteins) and the actin nucleating complex, Arp2/3. In this paper, we use a multiscale modelling approach in a 2D model of a motile cell. We describe the mutual interactions of the small G-proteins, and their effects on capping and side-branching of actin filaments. We incorporate the pushing exerted by oriented actin filament ends on the cell edge, and a Rho-dependent contraction force. Combining these biochemical and mechanical aspects, we investigate the dynamics of a model epidermal fish keratocyte through in silico experiments. Our model gives insight into how, in response to some cue, a cell can polarize, form a leading edge, and move; concomitantly it explains how a keratocyte cell can maintain its shape and polarity, even after removal of the initial stimulus, and how it can change direction quickly in response to changes in its environment. We show that establishment of polarity stems from interactions of Cdc42, Rac and Rho, while maintenance and robustness of polarity is due to the rapid cytosolic diffusion of the inactive (GDI-bound) forms of the small G-proteins. Our model produces a cell shape that closely resembles the keratocytes and correct speeds for biologically reasonable parameter values. Movies of the simulations can be obtained from http://theory.bio.uu.nl/stan/keratocyte.
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Affiliation(s)
- Athanasius F M Marée
- Theoretical Biology/Bioinformatics, Utrecht University, Utrecht, The Netherlands.
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11
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Li SP, Kim JH, Park MS, Bahk JY, Chung BC, Kim MO. Ethanol modulates the expression of GABAB receptor mRNAs in the prenatal rat brain in an age and area dependent manner. Neuroscience 2005; 134:857-66. [PMID: 16054771 DOI: 10.1016/j.neuroscience.2005.05.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2005] [Revised: 05/04/2005] [Accepted: 05/05/2005] [Indexed: 10/25/2022]
Abstract
Prenatal ethanol exposure has various deleterious effects on neuronal development. As GABA(B) receptor is known to play an important role during the development of the CNS, we now focused on its mRNA expression pattern in the rat brain during the late gestational days (GD) from 15.5 to GD 21.5. Ethanol's effect was also observed from GD 11.5 to GD 21.5. GABA(B1) receptor mRNA showed a high expression level in GD 15.5 and 19.5, while GABA(B2) receptor mRNA did in GD 15.5 and 21.5. The mRNAs levels depended on age and area during development. Ethanol exposure decreased GABA(B1) receptor from GD 11.5 to GD 19.5 with slight increases in GD 21.5. The decreasing effects were area dependent, with the highest effects in the forebrain including cortex, whereas slight effects were observed in the midbrain and hindbrain. The present results suggest an important role of GABA(B) receptor in the effects of ethanol on prenatal brain developmental processes.
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Affiliation(s)
- S P Li
- Division of Life Science, College of Natural Sciences and Applied Life Science (Brain Korea 21), Gyeongsang National University, Gyeongnam, Chinju, 660-701, South Korea
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McNamara RK, Lenox RH. The myristoylated alanine-rich C kinase substrate: a lithium-regulated protein linking cellular signaling and cytoskeletal plasticity. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.cnr.2004.09.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Gwinn RP, Spencer DD. Fighting fire with fire: brain stimulation for the treatment of epilepsy. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.cnr.2004.06.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Fiszman ML, Schousboe A. Role of calcium and kinases on the neurotrophic effect induced by gamma-aminobutyric acid. J Neurosci Res 2004; 76:435-41. [PMID: 15114615 DOI: 10.1002/jnr.20062] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
An increasing body of evidence supports a trophic action of gamma-aminobutyric acid (GABA) during nervous system development. The purported mediator of these trophic effects is a depolarizing response triggered by GABA, which elicits a calcium influx in immature CNS cells. This Mini-Review focuses on the neurotrophic role of neural activity and GABA and some of the most common intracellular cascades activated by depolarization and trophic factors. Several biological effects induced by GABA in the developing nervous system are reviewed, with particular emphasis on what is known about calcium-dependent neurotrophic effects induced by GABA and its intracellular mechanisms.
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Affiliation(s)
- Mónica L Fiszman
- Instituto de Investigaciones Farmacológicas-CONICET, Buenos Aires, Argentina.
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Shenai MB, Putchakayala KG, Hessler JA, Orr BG, Banaszak Holl MM, Baker JR. A Novel MEA/AFM Platform for Measurement of Real-Time, Nanometric Morphological Alterations of Electrically Stimulated Neuroblastoma Cells. IEEE Trans Nanobioscience 2004; 3:111-7. [PMID: 15382743 DOI: 10.1109/tnb.2004.828270] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Studies of electrically induced morphological changes in neurons have either been limited by the resolution of light microscopy or the cell fixation required for electron microscopy. Atomic force microscopy (AFM), however, mechanically maps cell topography, offering exquisite resolution of evolving processes in three dimensions. In this paper, we present a microelectrode array (MEA) based platform for the real-time detection of subtle, electrically induced variations in neuronal morphology, with AFM. This platform required the customized design and production of a silicon-based MEA, integration with a commercial AFM, and the development of biological techniques for culture of neuroblastoma (SH-SY5Y) cells onto the device. Biphasic pulse trains (1 Hz) of electric current were delivered to a microelectrode interfaced with a neuroblastoma cell, and the AFM continuously recorded a cross-sectional height profile. Proof-of-principle experiments demonstrate that electric stimulation may induce fluctuations ranging in the 100-300-nm range, 75-fold greater than the systemic resolution, but smaller than the resolution of light microscopy modalities. In addition, the real-time capabilities of AFM captured a collapse (30%-40%) of a neurite cross section, seconds after electric stimulation. Ultimately, this platform can be used to nanocharacterize cell responses to electric stimulation and other biochemical cues, for use in neuronal patterning and regeneration studies.
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Affiliation(s)
- Mahesh B Shenai
- Medical School, University of Michigan, Ann Arbor, MI 48105, USA.
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Lindsley TA, Comstock LL, Rising LJ. Morphologic and neurotoxic effects of ethanol vary with timing of exposure in vitro. Alcohol 2002; 28:197-203. [PMID: 12551761 DOI: 10.1016/s0741-8329(02)00279-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Results of investigations with animal models of fetal alcohol syndrome (FAS) seem to indicate that neuronal vulnerability to ethanol-induced cell death may be correlated with specific developmental events. In the present study, we sought to test this observation in a cell culture model of neuronal development in which morphogenesis as well as survival could be assessed. Using embryonic rat hippocampal pyramidal neurons in primary cultures, we compared the sensitivity of neurons to ethanol added, at 400 mg/dl, to the medium at different times relative to the development of axons and dendrites. Quantitative morphometric analysis was performed by using phase contrast at 12 h (0.5 day) and 24 h (1 day), or fluorescence microscopy after microtubule-associated protein-2 (MAP2) immunostaining at 6 and 14 days. Survival was assessed by counting the number of neurons per unit area of the substrate at 14 days. Addition of ethanol 1 day after plating, when most neurons had developed an axon, had no effect on survival up to 14 days in vitro, but resulted in significantly shorter, less branched dendrites than observed when ethanol was added 2 h after plating. Despite the shorter duration of ethanol exposure, the addition of ethanol on day 6, after rapid growth of dendrites and synapses had begun, resulted in loss of all but about one third of the neurons by 14 days. This supports the suggestion that increased neuronal vulnerability to the morphoregulatory effects of ethanol is correlated with the establishment of polarity, but that the sensitivity of neurons to the cytotoxic effects of ethanol occurs later, when dendrites and synapses are rapidly forming.
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Affiliation(s)
- Tara A Lindsley
- Center for Neuropharmacology & Neuroscience, Albany Medical College (MC-136), 47 New Scotland Avenue, Albany, NY 12208, USA.
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Borodinsky LN, Coso OA, Fiszman ML. Contribution of Ca2+ calmodulin-dependent protein kinase II and mitogen-activated protein kinase kinase to neural activity-induced neurite outgrowth and survival of cerebellar granule cells. J Neurochem 2002; 80:1062-70. [PMID: 11953456 DOI: 10.1046/j.1471-4159.2002.00795.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In this report we describe our studies on intracellular signals that mediate neurite outgrowth and long-term survival of cerebellar granule cells. The effect of voltage-gated calcium channel activation on neurite complexity was evaluated in cultured cerebellar granule cells grown for 48 h at low density; the parameter measured was the fractal dimension of the cell. We explored the contribution of two intracellular pathways, Ca2+ calmodulin-dependent protein kinase II and mitogen-activated protein kinase kinase (MEK1), to the effects of high [K+ ]e under serum-free conditions. We found that 25 mm KCl (25K) induced an increase in calcium influx through L subtype channels. In neurones grown for 24-48 h under low-density conditions, the activation of these channels induced neurite outgrowth through the activation of Ca2+ calmodulin-dependent protein kinase II. This also produced an increase in long-term neuronal survival with a partial contribution from the MEK1 pathway. We also found that the addition of 25K increased the levels of the phosphorylated forms of Ca2+ calmodulin-dependent protein kinase II and of the extracellular signal-regulated kinases 1 and 2. Neuronal survival under resting conditions is supported by the MEK1 pathway. We conclude that intracellular calcium oscillations can triggered different biological effects depending on the stage of maturation of the neuronal phenotype. Ca2+ calmodulin-dependent protein kinase II activation determines the growth of neurites and the development of neuronal complexity.
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Affiliation(s)
- Laura N Borodinsky
- Instituto de Investigaciones Farmacológicas, CONICET, FCEyN, UBA, Buenos Aires, Argentina
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Kerschbaum HH, Grissmer S, Engel E, Richter K, Lehner C, Jäger H. A Shaker homologue encodes an A-type current in Xenopus laevis. Brain Res 2002; 927:55-68. [PMID: 11814432 DOI: 10.1016/s0006-8993(01)03324-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In Xenopus laevis, several distinct K(+)-channels (xKv1.1, xKv1.2, xKv2,1, xKv2.2, xKv3.1) have been cloned, sequenced, and electrophysiologically characterized. K(+)-channels significantly shape neuronal excitability by setting the membrane potential, and latency and duration of action potentials. We identified a further Shaker homologue, xKv1.4, in X. laevis. The open reading frame encodes a K(+)-channel that shares 72% of its 698 amino acids with the human Shaker homologue, hKv1.4. Northern blot analysis revealed xKv1.4 in the brain, muscle, and spleen but not in the ovary, intestine, heart, liver, kidney, lung, and skin. Whole-cell patch clamp recording from rat basophilic leukaemia (RBL) cells transfected with xKv1.4 revealed a voltage-gated, outward rectifying, transient A-type, K(+) selective current. xKv1.4 was strongly dependent on extracellular K(+). Exposure of cells to K(+) free bath solution almost completely abolished the current, whereas in the presence of high K(+), inactivation in response to a maintained depolarizing step and the frequency-dependent cumulative inactivation decreased. Ion channels encoded by xKv1.4 are sensitive to 4-aminopyridine and quinidine but insensitive to tetraethylammonium and the peptide toxins, charybdotoxin, margatoxin, and dendrotoxin. In conclusion, our results indicate that the biophysical and pharmacological signature of xKv1.4 closely resemble those of the A-current described in Xenopus embryonic neurons and is similar to the human Shaker homologue, hKv1.4.
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Affiliation(s)
- Hubert H Kerschbaum
- Department of Molecular Neurobiology and Cellular Physiology, Institute of Zoology, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria.
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Schwab Y, Mouton J, Chasserot-Golaz S, Marty I, Maulet Y, Jover E. Calcium-dependent translocation of synaptotagmin to the plasma membrane in the dendrites of developing neurones. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2001; 96:1-13. [PMID: 11731003 DOI: 10.1016/s0169-328x(01)00244-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In neurones, the morphological complexity of the dendritic tree requires regulated growth and the appropriate targeting of membrane components. Accurate delivery of specific supplies depends on the translocation and fusion of transport vesicles. Vesicle SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptors) and target membrane SNAREs play a central role in the correct execution of fusion events, and mediate interactions with molecules that endow the system with appropriate regulation. Synaptotagmins, a family of Ca(2+)-sensor proteins that includes neurone-specific members involved in regulating neurotransmitter exocytosis, are among the molecules that can tune the fusion mechanism. Using immunocytochemistry, confocal and electron microscopy, the localisation of synaptotagmin I in the dendrites of cultured rat hypothalamic neurones was demonstrated. Synaptotagmin labelling is concentrated at dendritic branch points, and in microprocesses. Following depolarisation, the N-terminal domain of synaptotagmin was detected at the extracellular surface of the dendritic plasma membrane. The insertion of synaptotagmin in the plasma membrane was elicited by L-type Ca(2+) channel activation and by mobilisation of the internal ryanodine-sensitive Ca(2+)stores. Furthermore, the localisation of L-type Ca(2+) channels and of ryanodine receptors, relative to the localisation of synaptotagmin in dendrites, suggests that both Ca(2+) entry and intracellular Ca(2+) stores may contribute to the fusion of dendritic transport vesicles with the membrane. Fusion is likely to involve SNAP-25 and syntaxin 1 as both proteins were also identified in dendrites. Taken together these results suggest a putative regulatory role of synaptotagmins in the membrane fusion events that contribute to shaping the dendritic tree during development.
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Affiliation(s)
- Y Schwab
- UMR-CNRS 7519, Laboratoire de Neurophysiologie Cellulaire et Intégrée, Université Louis Pasteur, 21, rue René Descartes, F-67084, Cedex, Strasbourg, France
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Keith CH, Wilson MT. Factors controlling axonal and dendritic arbors. INTERNATIONAL REVIEW OF CYTOLOGY 2001; 205:77-147. [PMID: 11336394 DOI: 10.1016/s0074-7696(01)05003-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The sculpting and maintenance of axonal and dendritic arbors is largely under the control of molecules external to the cell. These factors include both substratum-associated and soluble factors that can enhance or inhibit the outgrowth of axons and dendrites. A large number of factors that modulate axonal outgrowth have been identified, and the first stages of the intracellular signaling pathways by which they modify process outgrowth have been characterized. Relatively fewer factors and pathways that affect dendritic outgrowth have been described. The factors that affect axonal arbors form an incompletely overlapping set with those that affect dendritic arbors, allowing selective control of the development and maintenance of these critical aspects of neuronal morphology.
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Affiliation(s)
- C H Keith
- Department of Cellular Biology. University of Georgia, Athens, 30605, USA
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21
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Tojima T, Ito E. A cyclic AMP-regulated negative feedforward system for neuritogenesis revealed in a neuroblastomaxglioma hybrid cell line. Neuroscience 2001; 104:583-91. [PMID: 11377857 DOI: 10.1016/s0306-4522(01)00061-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined the role of second messengers during the neuritogenesis that accompanies neuronal differentiation in a neuroblastomaxglioma hybrid cell line (NG108-15). NG108-15 cells extended neurites after treatment with dibutyryl cyclic AMP. This dibutyryl cyclic AMP treatment evoked the synthesis of voltage-dependent Ca(2+) channel proteins in the cells. The number of neurites was decreased by Ca(2+) influx under condition of high K(+). Interestingly, the increase of neurites stimulated by dibutyryl cyclic AMP and the decrease of neurites caused by high K(+) were both reversible. This is the first study to demonstrate that cyclic AMP regulates a negative feedforward system for neuritogenesis, which links with Ca(2+) signaling. Such a dual role of cyclic AMP may play an important part in precise neurite targeting.
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Affiliation(s)
- T Tojima
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, 060-0810, Sapporo, Japan
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22
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DeFazio RA, Pong K, Knusel B, Walsh JP. Neurotrophin-4/5 promotes dendritic outgrowth and calcium currents in cultured mesencephalic dopamine neurons. Neuroscience 2000; 99:297-304. [PMID: 10938435 DOI: 10.1016/s0306-4522(00)00191-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ca(2+) currents and their modulation by neurotrophin-4/5 were studied in cultured mesencephalic neurons. Tyrosine hydroxylase-positive neurons consistently had larger somas than tyrosine hydroxylase-negative neurons. Neurons with larger somas were therefore targeted for recording. In both control and neurotrophin-4/5-treated cultured neurons, isolation of Ca(2+) currents in cultured mesencephalic neurons revealed prominent low- and high-voltage-activated currents. These currents were separable based upon their voltage dependence of activation, the response to replacement of Ca(2+) with Ba(2+) and the response to Ca(2+) channel blockers. Replacement of Ca(2+) with Ba(2+) resulted in a slight reduction of low-voltage-activated currents and a significant enhancement of high-voltage-activated currents. Cd(2+) blocked a larger fraction of the high-voltage-activated current than Ni(2+). The synthetic conotoxins SNX-124 and SNX-230 selectively blocked high-voltage-activated currents. Morphological analysis of mesencephalic cultures pretreated with neurotrophin-4/5 revealed an increase in soma size and dendritic length in tyrosine hydroxylase-positive neurons. In agreement with the neurotrophin-4/5 induction of growth, neurotrophin-4/5 also increased cell capacitance in whole-cell recordings. Neurotrophin-4/5 significantly enhanced both low- and high-voltage-activated currents, but normalization for changes in capacitance revealed only a significant increase in high-voltage-activated current density. This study demonstrates the existence of low-voltage-activated and multiple classes of high-voltage-activated calcium currents in cultured mesencephalic neurons. Morphological and physiological data demonstrate that the increases in calcium currents due to neurotrophin-4/5 pretreatment are associated with somatodendritic growth, but an increase in high-voltage-activated Ca(2+) channel expression also occurred.
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Affiliation(s)
- R A DeFazio
- Ethel Percy Andrus Gerontology Center, USC Program in Neuroscience, University of Southern California, Los Angeles, CA 90089-0191, USA
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23
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Abstract
Axons are guided through their environment in response to signals provided by extracellular cues. These cues are transduced into motile responses by the tip of the growing axon, the growth cone, and can be either repulsive or attractive in nature. Recent studies have suggested that how an axon responds to any given signal depends on the internal state of the growth cone. This review discusses these studies and their importance for understanding how nerve connections are made in the developing embryo.Key words: growth cone, axon guidance, calcium, cyclic nucleotides.
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24
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McNamara RK, Jiang Y, Streit WJ, Lenox RH. Facial motor neuron regeneration induces a unique spatial and temporal pattern of myristoylated alanine-rich C kinase substrate expression. Neuroscience 2000; 97:581-9. [PMID: 10828540 DOI: 10.1016/s0306-4522(00)00039-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We have previously shown that the myristoylated alanine-rich C kinase substrate, a primary protein kinase C substrate in brain that binds and cross-links filamentous actin, is enriched in neuronal growth cones and is developmentally regulated in brain. Here we examined myristoylated alanine-rich C kinase substrate expression in the facial motor nucleus during axonal regeneration following facial nerve axotomy or facial nerve resection lesions, which impede regeneration, or following motor neuron degeneration induced by the retrograde neurotoxin ricin. For comparative purposes, the protein kinase C substrates myristoylated alanine-rich C kinase substrate-like protein and growth-associated protein-43 were examined in parallel. Myristoylated alanine-rich C kinase substrate messenger RNA exhibited a robust increase in both neurons and non-neuronal cells in the facial motor nucleus beginning four days after axotomy, peaked at seven days (2.5-fold), and declined back to baseline levels by 40 days. Myristoylated alanine-rich C kinase substrate protein similarly exhibited a twofold elevation in the facial motor nucleus determined four and 14 days post-axotomy. Following nerve resection, myristoylated alanine-rich C kinase substrate messenger RNA levels increased at seven days and returned to baseline levels by 40 days. Unlike myristoylated alanine-rich C kinase substrate messenger RNA, myristoylated alanine-rich C kinase substrate-like messenger RNA levels did not increase in the facial motor nucleus at any time point following nerve axotomy or resection, whereas growth-associated protein-43 messenger RNA exhibited a rapid (one day) and prolonged (40 days) elevation in facial motor nucleus neurons following either nerve axotomy or resection. Ricin-induced degeneration of facial motor neurons elevated myristoylated alanine-rich C kinase substrate and myristoylated alanine-rich C kinase substrate-like messenger RNAs in both microglia (lectin-positive) and astrocytes (glial fibrillary acidic protein-positive).Collectively, these data demonstrate that myristoylated alanine-rich C kinase substrate exhibits a unique expression profile in the facial motor nucleus following facial nerve lesions, and it is proposed that myristoylated alanine-rich C kinase substrate may serve to mediate actin-membrane cytoskeletal plasticity in both neurons and glial cells in response to protein kinaseC-mediated signaling during nerve regeneration and degeneration.
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Affiliation(s)
- R K McNamara
- Department of Psychiatry, University of Pennsylvania School of Medicine, Clinical Research Building, Philadelphia, PA 19104-6140, USA.
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25
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Wilson MT, Kisaalita WS, Keith CH. Glutamate-induced changes in the pattern of hippocampal dendrite outgrowth: a role for calcium-dependent pathways and the microtubule cytoskeleton. JOURNAL OF NEUROBIOLOGY 2000; 43:159-72. [PMID: 10770845 DOI: 10.1002/(sici)1097-4695(200005)43:2<159::aid-neu6>3.0.co;2-n] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Glutamate regulation of a variety of aspects of dendrite development may be involved in neuronal plasticity and neuropathology. In this study, we examine the calcium-dependent pathways and alterations in the microtubule (MT) cytoskeleton that may mediate glutamate-induced changes in the pattern of dendrite outgrowth. We used Fura-2 AM and inhibitors of the calcium-dependent proteins, calmodulin and calpain, to identify the role of specific calcium-dependent pathways in glutamate-regulated dendrite outgrowth. Additionally, we used a quantitative fluorescence technique to correlate changes in MT levels with glutamate-induced changes in dendrite outgrowth. We show that the intracellular calcium concentration ([Ca(2+)](i)) changes in a biphasic manner over a 12-h period in the presence of glutamate. A transient increase in [Ca(2+)](i) over the first hour of glutamate exposure correlated with a calmodulin-associated increase in the rate of dendrite outgrowth, whereas a sustained increase in [Ca(2+)](i) was correlated with calpain-associated dendrite retraction. Quantitative fluorescence measurements showed no net change in the level of MTs during calmodulin-associated increases in dendrite outgrowth, but showed a significant decline in the level of MTs during calpain-associated dendrite retraction. These findings provide insights into the intracellular mechanisms involved in activity-dependent regulation of dendrite morphology during development and after pathology.
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Affiliation(s)
- M T Wilson
- BD Transduction Laboratories, Lexington, Kentucky 40503, USA
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26
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Burgess DL, Noebels JL. Single gene defects in mice: the role of voltage-dependent calcium channels in absence models. Epilepsy Res 1999; 36:111-22. [PMID: 10515159 DOI: 10.1016/s0920-1211(99)00045-5] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nineteen genes encoding alpha1, beta, gamma, or alpha2delta voltage-dependent calcium channel subunits have been identified to date. Recent studies have found that three of these genes are mutated in mice with generalised cortical spike-wave discharges (models of human absence epilepsy), emphasising the importance of calcium channels in regulating the expression of this inherited seizure phenotype. The tottering (tg) locus encodes the calcium channel alpha1 subunit gene Cacna1a, lethargic (lh) encodes the beta subunit gene Cacnb4, and stargazer (stg) encodes the gamma subunit gene Cacng2. These calcium channel mutants should provide important insights into the basic mechanisms of neuronal synchronisation, and the genes may be considered candidates for involvement in similar human disorders. The mutant models offer an important opportunity to elucidate the molecular, developmental, and physiological mechanisms underlying one subtype of absence epilepsy. Since calcium channels are involved in numerous cellular functions, including proliferation and differentiation, membrane excitability, neurite outgrowth and synaptogenesis, signal transduction, and gene expression, their role in generating the absence epilepsy phenotype may be complex. A comparative analysis of channel function and neural excitability patterns in tottering, lethargic, and stargazer brain should be useful in identifying the common elements of calcium channel involvement in these absence models.
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Affiliation(s)
- D L Burgess
- Department of Neurology, Baylor College of Medicine, Houston, TX 77303, USA.
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27
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Falk T, Muller YL, Yool AJ. Differential expression of three classes of voltage-gated Ca(2+) channels during maturation of the rat cerebellum in vitro. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1999; 115:161-70. [PMID: 10407133 DOI: 10.1016/s0165-3806(99)00060-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Voltage-gated Ca(2+) channels provide a mode of Ca(2+) influx that is essential for intracellular signaling in many cells. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to assess the relative amounts of mRNAs encoding three classes of Ca(2+) channels (alpha1A, alpha1B and alpha1E) during development, in cultures established from prenatal rat cerebellar cortex. Ca(2+) channel transcript levels were standardized to a constitutive marker (cyclophilin). For all three classes of Ca(2+) channels, transcript levels were highest at early stages (4-10 days in vitro) and declined with age. This developmental pattern was differentially regulated by a depolarizing agent, tetraethylammonium chloride (TEA, 1 mM). Chronic depolarization yielded a significant elevation in transcript levels for alpha1B (N-type) and alpha1E (R-type) Ca(2+) channels during neuronal maturation (10-21 days in vitro), but dramatically suppressed transcript levels for the alpha1A (P-type) Ca(2+) channel at all stages of development. The effects of TEA on alpha1A, alpha1B and alpha1E transcript levels were mimicked by increasing external K(+) (from 5 to 10 mM). The regulatory effects of depolarization on transcript levels were dependent on extracellular Ca(2+) for alpha1E but not for alpha1A. For alpha1B, transcript levels depended on extracellular Ca(2+) only for increased K(+) as the depolarizing stimulus, but not for TEA. These results suggest that levels of Ca(2+) channel transcripts in rat cerebellum are developmentally regulated in vitro and can be influenced differentially by transmembrane signaling via chronic depolarization and Ca(2+) entry. Dynamic regulation of Ca(2+) channel expression may be relevant to the different functional roles of Ca(2+) channels and their regional localization within neurons.
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Affiliation(s)
- T Falk
- Department of Physiology, University of Arizona College of Medicine, Tucson, AZ 85724-5051, USA
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28
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Johnson BD. The company they keep: ion channels and their intracellular regulatory partners. ADVANCES IN SECOND MESSENGER AND PHOSPHOPROTEIN RESEARCH 1999; 33:203-28. [PMID: 10218120 DOI: 10.1016/s1040-7952(99)80011-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- B D Johnson
- Department of Physiology and Neurobiology, University of Connecticut, Storrs 06269, USA
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29
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Matheson SF, Levine RB. Steroid hormone enhancement of neurite outgrowth in identified insect motor neurons involves specific effects on growth cone form and function. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1097-4695(199901)38:1<27::aid-neu3>3.0.co;2-u] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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30
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Affiliation(s)
- M M Fróes
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil
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31
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Zohar O. Elimination of sensory inputs induces growth and synaptic changes in crayfish motor axons. Proc Biol Sci 1998. [DOI: 10.1098/rspb.1998.0422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Ofer Zohar
- Inter–University Red Sea Research Center at Eilat, Eilat 88103, Israel
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32
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Mattson MP. Free radicals, calcium, and the synaptic plasticity-cell death continuum: emerging roles of the transcription factor NF kappa B. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1998; 42:103-68. [PMID: 9476172 DOI: 10.1016/s0074-7742(08)60609-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- M P Mattson
- Sanders-Brown Research Center on Aging, University of Kentucky, Lexington 40536, USA
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33
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Abstract
In this study, we have tested how various identified leech neurons in culture grow on surfaces that they normally contact in situ. Neurons were cultured either on ganglion capsules from which neurons had been removed or on skin. On these substrates, outgrowth patterns were characteristic for each cell type. Retzius cells plated on capsules extended bundles of thick, fasciculated processes with few branching points and in the opposite direction a tangle of fine neurites. Anterior pagoda (AP) neurons plated on capsules extended two single processes in opposite directions but failed to grow on skin. Sensory P and N neurons on capsules extended multiple processes. On skin, P neurons extended only two long branches in opposite directions over the superficial body wall. N neurons on skin extended multiple processes. Varicosities were common in the processes of P and N neurons on capsules or skin. The branching patterns described here bore closer resemblance to those in the developing or adult nervous system than to those on Concanavalin A or laminin-enriched extract. Pairs of Retzius or AP neurons plated at a distance on the same capsule extended neurites from one neuron toward the other and formed contacts. Such directed growth failed in hybrid pairs of Retzius and AP neurons or in pairs plated on laminin-enriched extract or Concanavalin A. Our results suggest that multiple growth-promoting molecules anchored to the extracellular matrix may cooperate in regulating the branching pattern of neurons, fasciculation, and direction of growth.
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34
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Stevens GR, Zhang C, Berg MM, Lambert MP, Barber K, Cantallops I, Routtenberg A, Klein WL. CNS neuronal focal adhesion kinase forms clusters that co-localize with vinculin. J Neurosci Res 1996; 46:445-55. [PMID: 8950704 DOI: 10.1002/(sici)1097-4547(19961115)46:4<445::aid-jnr6>3.0.co;2-g] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that appears to play a central role in integrin-mediated signal transduction in non-neuronal cells, linking the extracellular matrix to the actin-based cytoskeleton at focal adhesion contacts. Biochemical analysis has revealed the presence of FAK immunoreactivity in cells of neuronal lineage (Zhang et al., 1994) and in the CNS (Burgaya et al. 1995; Grant et al., 1995). In the current work, we have examined the immunodistribution of FAK in nerve cell cultures and tissue sections from the rat CNS. Cultures of B103 CNS neuroblastoma cells and primary cultures of hippocampal neurons both showed abundant FAK immunoreactivity in nerve cell bodies. Immunoreactivity also extended into neurites and growth cones. The most striking feature of FAK distribution was the presence of short, punctate clusters of high FAK concentration. These FAK clusters were maintained in triton-extracted cell ghosts, indicating association with the cytoskeleton. Double-label confocal imaging showed that clusters of FAK coincided with clusters of vinculin, another actin-associated signal transduction molecule implicated in control of growth cone motility. Data from hippocampal sections verified the presence of FAK in adult neurons where it was enriched in somato-dendritic domains and showed a non-uniform distribution. Quantitative FAK immunoprecipitation to compare adult with embryonic brain showed a 7-fold developmental down-regulation of FAK and a 21-fold down-regulation of FAK TyrP. The data suggest that neuronal FAK may participate in signal transduction complexes relevant to neuronal morphogenesis and plasticity.
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Affiliation(s)
- G R Stevens
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA
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35
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Abstract
Nerve impulses regulate expression of genes that control receptors, channels, enzymes, and structural proteins. This activity-dependent feedback allows adaptation to changing requirements and environmental conditions. The signal transduction mechanisms carrying information from the cell membrane to the nucleus are becoming well characterized, but a more dynamic view of intracellular signaling is emerging to explain cellular responses to specific patterns of neural impulses. This review analyzes this interface between electrophysiology and molecular cell biology to examine the signals, substrates, and processes that enable the nervous system to regulate its structure and function as a consequence of its own operation.
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Affiliation(s)
- R. Douglas Fields
- Laboratory of Developmental Neurobiology National Institutes of Health, NICHD Bethesda, Maryland
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