1
|
Gautham AK, Miner LE, Franco MN, Thornquist SC, Crickmore MA. Dopamine biases decisions by limiting temporal integration. Nature 2024; 632:850-857. [PMID: 39085606 DOI: 10.1038/s41586-024-07749-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 06/24/2024] [Indexed: 08/02/2024]
Abstract
Motivations bias our responses to stimuli, producing behavioural outcomes that match our needs and goals. Here we describe a mechanism behind this phenomenon: adjusting the time over which stimulus-derived information is permitted to accumulate towards a decision. As a Drosophila copulation progresses, the male becomes less likely to continue mating through challenges1-3. We show that a set of copulation decision neurons (CDNs) flexibly integrates information about competing drives to mediate this decision. Early in mating, dopamine signalling restricts CDN integration time by potentiating Ca2+/calmodulin-dependent protein kinase II (CaMKII) activation in response to stimulatory inputs, imposing a high threshold for changing behaviours. Later into mating, the timescale over which the CDNs integrate termination-promoting information expands, increasing the likelihood of switching behaviours. We suggest scalable windows of temporal integration at dedicated circuit nodes as a key but underappreciated variable in state-based decision-making.
Collapse
Affiliation(s)
- Aditya K Gautham
- F. M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Lauren E Miner
- F. M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Marco N Franco
- F. M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Stephen C Thornquist
- F. M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
- Laboratory of Integrative Brain Function, The Rockefeller University, New York, NY, USA.
| | - Michael A Crickmore
- F. M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
| |
Collapse
|
2
|
Gautham AK, Miner LE, Franco MN, Thornquist SC, Crickmore MA. Molecular control of temporal integration matches decision-making to motivational state. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.01.582988. [PMID: 38496671 PMCID: PMC10942309 DOI: 10.1101/2024.03.01.582988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Motivations bias our responses to stimuli, producing behavioral outcomes that match our needs and goals. We describe a mechanism behind this phenomenon: adjusting the time over which stimulus-derived information is permitted to accumulate toward a decision. As a Drosophila copulation progresses, the male becomes less likely to continue mating through challenges. We show that a set of Copulation Decision Neurons (CDNs) flexibly integrates information about competing drives to mediate this decision. Early in mating, dopamine signaling restricts CDN integration time by potentiating CaMKII activation in response to stimulatory inputs, imposing a high threshold for changing behaviors. Later into mating, the timescale over which the CDNs integrate termination-promoting information expands, increasing the likelihood of switching behaviors. We suggest scalable windows of temporal integration at dedicated circuit nodes as a key but underappreciated variable in state-based decision-making.
Collapse
Affiliation(s)
- Aditya K. Gautham
- FM Kirby Neurobiology Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115
| | - Lauren E. Miner
- FM Kirby Neurobiology Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115
| | - Marco N. Franco
- FM Kirby Neurobiology Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115
| | | | - Michael A. Crickmore
- FM Kirby Neurobiology Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115
| |
Collapse
|
3
|
Aponte-Santiago NA, Littleton JT. Synaptic Properties and Plasticity Mechanisms of Invertebrate Tonic and Phasic Neurons. Front Physiol 2020; 11:611982. [PMID: 33391026 PMCID: PMC7772194 DOI: 10.3389/fphys.2020.611982] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 11/24/2020] [Indexed: 12/15/2022] Open
Abstract
Defining neuronal cell types and their associated biophysical and synaptic diversity has become an important goal in neuroscience as a mechanism to create comprehensive brain cell atlases in the post-genomic age. Beyond broad classification such as neurotransmitter expression, interneuron vs. pyramidal, sensory or motor, the field is still in the early stages of understanding closely related cell types. In both vertebrate and invertebrate nervous systems, one well-described distinction related to firing characteristics and synaptic release properties are tonic and phasic neuronal subtypes. In vertebrates, these classes were defined based on sustained firing responses during stimulation (tonic) vs. transient responses that rapidly adapt (phasic). In crustaceans, the distinction expanded to include synaptic release properties, with tonic motoneurons displaying sustained firing and weaker synapses that undergo short-term facilitation to maintain muscle contraction and posture. In contrast, phasic motoneurons with stronger synapses showed rapid depression and were recruited for short bursts during fast locomotion. Tonic and phasic motoneurons with similarities to those in crustaceans have been characterized in Drosophila, allowing the genetic toolkit associated with this model to be used for dissecting the unique properties and plasticity mechanisms for these neuronal subtypes. This review outlines general properties of invertebrate tonic and phasic motoneurons and highlights recent advances that characterize distinct synaptic and plasticity pathways associated with two closely related glutamatergic neuronal cell types that drive invertebrate locomotion.
Collapse
Affiliation(s)
- Nicole A. Aponte-Santiago
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, CA, United States
| | - J. Troy Littleton
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
| |
Collapse
|
4
|
TRPV4 disrupts mitochondrial transport and causes axonal degeneration via a CaMKII-dependent elevation of intracellular Ca 2. Nat Commun 2020; 11:2679. [PMID: 32471994 PMCID: PMC7260201 DOI: 10.1038/s41467-020-16411-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 05/01/2020] [Indexed: 12/14/2022] Open
Abstract
The cation channel transient receptor potential vanilloid 4 (TRPV4) is one of the few identified ion channels that can directly cause inherited neurodegeneration syndromes, but the molecular mechanisms are unknown. Here, we show that in vivo expression of a neuropathy-causing TRPV4 mutant (TRPV4R269C) causes dose-dependent neuronal dysfunction and axonal degeneration, which are rescued by genetic or pharmacological blockade of TRPV4 channel activity. TRPV4R269C triggers increased intracellular Ca2+ through a Ca2+/calmodulin-dependent protein kinase II (CaMKII)-mediated mechanism, and CaMKII inhibition prevents both increased intracellular Ca2+ and neurotoxicity in Drosophila and cultured primary mouse neurons. Importantly, TRPV4 activity impairs axonal mitochondrial transport, and TRPV4-mediated neurotoxicity is modulated by the Ca2+-binding mitochondrial GTPase Miro. Our data highlight an integral role for CaMKII in neuronal TRPV4-associated Ca2+ responses, the importance of tightly regulated Ca2+ dynamics for mitochondrial axonal transport, and the therapeutic promise of TRPV4 antagonists for patients with TRPV4-related neurodegenerative diseases. Mutations in the TRPV4 channel cause inherited neurodegeneration syndromes, but the molecular mechanisms are unknown. Here the authors reveal that TRPV4 activation causes dose-dependent, CaMKII-mediated neuronal dysfunction and axonal degeneration via disruption of mitochondrial axonal transport.
Collapse
|
5
|
Thornquist SC, Langer K, Zhang SX, Rogulja D, Crickmore MA. CaMKII Measures the Passage of Time to Coordinate Behavior and Motivational State. Neuron 2020; 105:334-345.e9. [PMID: 31786014 PMCID: PMC7374950 DOI: 10.1016/j.neuron.2019.10.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 08/30/2019] [Accepted: 10/09/2019] [Indexed: 12/18/2022]
Abstract
Electrical events in neurons occur on the order of milliseconds, but the brain can process and reproduce intervals millions of times longer. We present what we believe to be the first neuronal mechanism for timing intervals longer than a few seconds. The activation and gradual relaxation of calcium-independent CaMKII measure a 6-min time window to coordinate two male-specific events during Drosophila mating: sperm transfer and a simultaneous decrease in motivation. We localize these functions to four neurons whose electrical activity is necessary only to report the conclusion of the decline in CaMKII's activity, not for the measurement of the interval. The computation of elapsed time is therefore largely invisible to standard methods of monitoring neuronal activity. Its broad conservation, ubiquitous expression, and tunable duration of activity suggest that CaMKII may time a wide variety of behavioral and cognitive processes.
Collapse
Affiliation(s)
- Stephen C Thornquist
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Kirill Langer
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Stephen X Zhang
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Dragana Rogulja
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Michael A Crickmore
- FM Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| |
Collapse
|
6
|
Song Y, Li D, Farrelly O, Miles L, Li F, Kim SE, Lo TY, Wang F, Li T, Thompson-Peer KL, Gong J, Murthy SE, Coste B, Yakubovich N, Patapoutian A, Xiang Y, Rompolas P, Jan LY, Jan YN. The Mechanosensitive Ion Channel Piezo Inhibits Axon Regeneration. Neuron 2019; 102:373-389.e6. [PMID: 30819546 PMCID: PMC6487666 DOI: 10.1016/j.neuron.2019.01.050] [Citation(s) in RCA: 123] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 11/27/2018] [Accepted: 01/23/2019] [Indexed: 01/09/2023]
Abstract
Neurons exhibit a limited ability of repair. Given that mechanical forces affect neuronal outgrowth, it is important to investigate whether mechanosensitive ion channels may regulate axon regeneration. Here, we show that DmPiezo, a Ca2+-permeable non-selective cation channel, functions as an intrinsic inhibitor for axon regeneration in Drosophila. DmPiezo activation during axon regeneration induces local Ca2+ transients at the growth cone, leading to activation of nitric oxide synthase and the downstream cGMP kinase Foraging or PKG to restrict axon regrowth. Loss of DmPiezo enhances axon regeneration of sensory neurons in the peripheral and CNS. Conditional knockout of its mammalian homolog Piezo1 in vivo accelerates regeneration, while its pharmacological activation in vitro modestly reduces regeneration, suggesting the role of Piezo in inhibiting regeneration may be evolutionarily conserved. These findings provide a precedent for the involvement of mechanosensitive channels in axon regeneration and add a potential target for modulating nervous system repair.
Collapse
Affiliation(s)
- Yuanquan Song
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Dan Li
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA,These authors contributed equally
| | - Olivia Farrelly
- Department of Dermatology, University of Pennsylvania, Philadelphia, PA 19104, USA,These authors contributed equally
| | - Leann Miles
- The Graduate Group in Biochemistry and Molecular Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA,These authors contributed equally
| | - Feng Li
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA,Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Sung Eun Kim
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Tsz Y. Lo
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Fei Wang
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Tun Li
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Katherine L. Thompson-Peer
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jiaxin Gong
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Swetha E. Murthy
- Department of Neuroscience, The Scripps Research Institute, Howard Hughes Medical Institute, La Jolla, CA 92037, USA
| | - Bertrand Coste
- Department of Neuroscience, The Scripps Research Institute, Howard Hughes Medical Institute, La Jolla, CA 92037, USA,Present address: Aix Marseille Université, CNRS, LNC-UMR 7291, 13344 Marseille, France
| | - Nikita Yakubovich
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Ardem Patapoutian
- Department of Neuroscience, The Scripps Research Institute, Howard Hughes Medical Institute, La Jolla, CA 92037, USA
| | - Yang Xiang
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Panteleimon Rompolas
- Department of Dermatology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Lily Yeh Jan
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA,Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Yuh Nung Jan
- Departments of Physiology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA; Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
| |
Collapse
|
7
|
Ravi P, Trivedi D, Hasan G. FMRFa receptor stimulated Ca2+ signals alter the activity of flight modulating central dopaminergic neurons in Drosophila melanogaster. PLoS Genet 2018; 14:e1007459. [PMID: 30110323 PMCID: PMC6110513 DOI: 10.1371/journal.pgen.1007459] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 08/27/2018] [Accepted: 06/29/2018] [Indexed: 11/19/2022] Open
Abstract
Neuropeptide signaling influences animal behavior by modulating neuronal activity and thus altering circuit dynamics. Insect flight is a key innate behavior that very likely requires robust neuromodulation. Cellular and molecular components that help modulate flight behavior are therefore of interest and require investigation. In a genetic RNAi screen for G-protein coupled receptors that regulate flight bout durations, we earlier identified several receptors, including the receptor for the neuropeptide FMRFa (FMRFaR). To further investigate modulation of insect flight by FMRFa we generated CRISPR-Cas9 mutants in the gene encoding the Drosophila FMRFaR. The mutants exhibit significant flight deficits with a focus in dopaminergic cells. Expression of a receptor specific RNAi in adult central dopaminergic neurons resulted in progressive loss of sustained flight. Further, genetic and cellular assays demonstrated that FMRFaR stimulates intracellular calcium signaling through the IP3R and helps maintain neuronal excitability in a subset of dopaminergic neurons for positive modulation of flight bout durations.
Collapse
Affiliation(s)
- Preethi Ravi
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | - Deepti Trivedi
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| |
Collapse
|
8
|
Lowe SA, Hodge JJL, Usowicz MM. A third copy of the Down syndrome cell adhesion molecule (Dscam) causes synaptic and locomotor dysfunction in Drosophila. Neurobiol Dis 2017; 110:93-101. [PMID: 29196216 PMCID: PMC5773243 DOI: 10.1016/j.nbd.2017.11.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 10/13/2017] [Accepted: 11/27/2017] [Indexed: 02/06/2023] Open
Abstract
Down syndrome (DS) is caused by triplication of chromosome 21 (HSA21). It is characterised by intellectual disability and impaired motor coordination that arise from changes in brain volume, structure and function. However, the contribution of each HSA21 gene to these various phenotypes and to the causal alterations in neuronal and synaptic structure and function are largely unknown. Here we have investigated the effect of overexpression of the HSA21 gene DSCAM (Down syndrome cell adhesion molecule), on glutamatergic synaptic transmission and motor coordination, using Drosophila expressing three copies of Dscam1. Electrophysiological recordings of miniature and evoked excitatory junction potentials at the glutamatergic neuromuscular junction of Drosophila larvae showed that the extra copy of Dscam1 changed the properties of spontaneous and electrically-evoked transmitter release and strengthened short-term synaptic depression during high-frequency firing of the motor nerve. Behavioural analyses uncovered impaired locomotor coordination despite preserved gross motor function. This work identifies DSCAM as a candidate causative gene in DS that is sufficient to modify synaptic transmission and synaptic plasticity and cause a DS behavioural phenotype. Drosophila expressing a third copy of Dscam have altered neuromuscular transmission. Drosophila expressing a third copy of Dscam have deficits in locomotor coordination. Drosophila are a powerful system for studying single-gene effects in Down syndrome.
Collapse
Affiliation(s)
- Simon A Lowe
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - James J L Hodge
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK.
| | - Maria M Usowicz
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, University Walk, Bristol BS8 1TD, UK.
| |
Collapse
|
9
|
Oka M, Fujisaki N, Maruko-Otake A, Ohtake Y, Shimizu S, Saito T, Hisanaga SI, Iijima KM, Ando K. Ca2+/calmodulin-dependent protein kinase II promotes neurodegeneration caused by tau phosphorylated at Ser262/356 in a transgenic Drosophila model of tauopathy. J Biochem 2017; 162:335-342. [PMID: 28992057 DOI: 10.1093/jb/mvx038] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 05/19/2017] [Indexed: 01/07/2023] Open
Abstract
Abnormal deposition of the microtubule-associated protein tau is a common pathological feature of multiple neurodegenerative diseases, including Alzheimer's disease (AD), and plays critical roles in their pathogenesis. Disruption of calcium homeostasis and the downstream kinase Ca2+/calmodulin-dependent protein kinase II (CaMKII) coincides with pathological phosphorylation of tau in AD brains. However, it remains unclear whether and how dysregulation of CaMKII affects tau toxicity. Using a Drosophila model, we found that CaMKII promotes neurodegeneration caused by tau phosphorylated at the AD-associated sites Ser262/356. Overexpression of CaMKII promoted, while RNA-mediated knockdown of CaMKII and inhibition of CaMKII activity by expression of an inhibitory peptide suppressed, tau-mediated neurodegeneration. Blocking tau phosphorylation at Ser262/356 by alanine substitutions suppressed promotion of tau toxicity by CaMKII, suggesting that tau phosphorylation at these sites is required for this phenomenon. However, neither knockdown nor overexpression of CaMKII affected tau phosphorylation levels at Ser262/356, suggesting that CaMKII is not directly involved in tau phosphorylation at Ser262/356 in this model. These results suggest that a pathological cascade of events, including elevated levels of tau phosphorylated at Ser262/356 and aberrant activation of CaMKII, work in concert to promote tau-mediated neurodegeneration.
Collapse
Affiliation(s)
- Mikiko Oka
- Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Naoki Fujisaki
- Department of Alzheimer's Disease Research, National Center for Geriatrics and Gerontology, 7-430 Morioka-machi, Obu, Aichi 474-8511, Japan.,Department of Experimental Gerontology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan
| | - Akiko Maruko-Otake
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Yosuke Ohtake
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Sawako Shimizu
- Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Taro Saito
- Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Shin-Ichi Hisanaga
- Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Koichi M Iijima
- Department of Alzheimer's Disease Research, National Center for Geriatrics and Gerontology, 7-430 Morioka-machi, Obu, Aichi 474-8511, Japan.,Department of Experimental Gerontology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan
| | - Kanae Ando
- Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| |
Collapse
|
10
|
The Long 3'UTR mRNA of CaMKII Is Essential for Translation-Dependent Plasticity of Spontaneous Release in Drosophila melanogaster. J Neurosci 2017; 37:10554-10566. [PMID: 28954869 DOI: 10.1523/jneurosci.1313-17.2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 09/05/2017] [Accepted: 09/19/2017] [Indexed: 12/27/2022] Open
Abstract
A null mutation of the Drosophila calcium/calmodulin-dependent protein kinase II gene (CaMKII) was generated using homologous recombination. Null animals survive to larval and pupal stages due to a large maternal contribution of CaMKII mRNA, which consists of a short 3'-untranslated region (UTR) form lacking regulatory elements that guide local translation. The selective loss of the long 3'UTR mRNA in CaMKII-null larvae allows us to test its role in plasticity. Development and evoked function of the larval neuromuscular junction are surprisingly normal, but the resting rate of miniature excitatory junctional potentials (mEJPs) is significantly lower in CaMKII mutants. Mutants also lack the ability to increase mEJP rate in response to spaced depolarization, a type of activity-dependent plasticity shown to require both transcription and translation. Consistent with this, overexpression of miR-289 in wild-type animals blocks plasticity of spontaneous release. In addition to the defects in regulation of mEJP rate, CaMKII protein is largely lost from synapses in the mutant. All phenotypes are non-sex-specific and rescued by a fosmid containing the entire wild-type CaMKII locus, but only viability and CaMKII localization are rescued by genomic fosmids lacking the long 3'UTR. This suggests that synaptic CaMKII accumulates by two distinct mechanisms: local synthesis requiring the long 3'UTR form of CaMKII mRNA and a process that requires zygotic transcription of CaMKII mRNA. The origin of synaptic CaMKII also dictates its functionality. Locally translated CaMKII has a privileged role in regulation of spontaneous release, which cannot be fulfilled by synaptic CaMKII from the other pool.SIGNIFICANCE STATEMENT As a regulator of synaptic development and plasticity, CaMKII has important roles in both normal and pathological function of the nervous system. CaMKII shows high conservation between Drosophila and humans, underscoring the usefulness of Drosophila in modeling its function. Drosophila CaMKII-null mutants remain viable throughout development, enabling morphological and electrophysiological characterization. Although the structure of the synapse is normal, maternally contributed CaMKII does not localize to synapses. Zygotic production of CaMKII mRNA with a long 3'-untranslated region is necessary for modulating spontaneous neurotransmission in an activity-dependent manner, but not for viability. These data argue that regulation of CaMKII localization and levels by local transcriptional processes is conserved. This is the first demonstration of distinct functions for Drosophila CaMKII mRNA variants.
Collapse
|
11
|
In Vivo Calcium Signaling during Synaptic Refinement at the Drosophila Neuromuscular Junction. J Neurosci 2017; 37:5511-5526. [PMID: 28476946 DOI: 10.1523/jneurosci.2922-16.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Revised: 04/17/2017] [Accepted: 04/18/2017] [Indexed: 11/21/2022] Open
Abstract
Neural activity plays a key role in pruning aberrant synapses in various neural systems, including the mammalian cortex, where low-frequency (0.01 Hz) calcium oscillations refine topographic maps. However, the activity-dependent molecular mechanisms remain incompletely understood. Activity-dependent pruning also occurs at embryonic Drosophila neuromuscular junctions (NMJs), where low-frequency Ca2+ oscillations are required for synaptic refinement and the response to the muscle-derived chemorepellant Sema2a. We examined embryonic growth cone filopodia in vivo to directly observe their exploration and to analyze the episodic Ca2+ oscillations involved in refinement. Motoneuron filopodia repeatedly contacted off-target muscle fibers over several hours during late embryogenesis, with episodic Ca2+ signals present in both motile filopodia as well as in later-stabilized synaptic boutons. The Ca2+ transients matured over several hours into regular low-frequency (0.03 Hz) oscillations. In vivo imaging of intact embryos of both sexes revealed that the formation of ectopic filopodia is increased in Sema2a heterozygotes. We provide genetic evidence suggesting a complex presynaptic Ca2+-dependent signaling network underlying refinement that involves the phosphatases calcineurin and protein phosphatase-1, as well the serine/threonine kinases CaMKII and PKA. Significantly, this network influenced the neuron's response to the muscle's Sema2a chemorepellant, critical for the removal of off-target contacts.SIGNIFICANCE STATEMENT To address the question of how synaptic connectivity is established during development, we examined the behavior of growth cone filopodia during the exploration of both correct and off-target muscle fibers in Drosophila embryos. We demonstrate that filopodia repeatedly contact off-target muscles over several hours, until they ultimately retract. We show that intracellular signals are observed in motile and stabilized "ectopic" contacts. Several genetic experiments provide insight in the molecular pathway underlying network refinement, which includes oscillatory calcium signals via voltage-gated calcium channels as a key component. Calcium orchestrates the activity of several kinases and phosphatases, which interact in a coordinated fashion to regulate chemorepulsion exerted by the muscle.
Collapse
|
12
|
Malik BR, Hodge JJL. CASK and CaMKII function in Drosophila memory. Front Neurosci 2014; 8:178. [PMID: 25009461 PMCID: PMC4070058 DOI: 10.3389/fnins.2014.00178] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2014] [Accepted: 06/06/2014] [Indexed: 12/04/2022] Open
Abstract
Calcium (Ca2+) and Calmodulin (CaM)-dependent serine/threonine kinase II (CaMKII) plays a central role in synaptic plasticity and memory due to its ability to phosphorylate itself and regulate its own kinase activity. Autophosphorylation at threonine 287 (T287) switches CaMKII to a Ca2+ independent and constitutively active state replicated by overexpression of a phosphomimetic CaMKII-T287D transgene or blocked by expression of a T287A transgene. A second pair of sites, T306 T307 in the CaM binding region once autophosphorylated, prevents CaM binding and inactivates the kinase during synaptic plasticity and memory, and can be blocked by a TT306/7AA transgene. Recently the synaptic scaffolding molecule called CASK (Ca2+/CaM-associated serine kinase) has been shown to control both sets of CaMKII autophosphorylation events during neuronal growth, Ca2+ signaling and memory in Drosophila. Deletion of either full length CASK or just its CaMK-like and L27 domains removed middle-term memory (MTM) and long-term memory (LTM), with CASK function in the α′/ß′ mushroom body neurons being required for memory. In a similar manner directly changing the levels of CaMKII autophosphorylation (T287D, T287A, or TT306/7AA) in the α′/ß′ neurons also removed MTM and LTM. In the CASK null mutant expression of either the Drosophila or human CASK transgene in the α′/ß′ neurons was found to completely rescue memory, confirming that CASK signaling in α′/β′ neurons is necessary and sufficient for Drosophila memory formation and that the neuronal function of CASK is conserved between Drosophila and human. Expression of human CASK in Drosophila also rescued the effect of CASK deletion on the activity state of CaMKII, suggesting that human CASK may also regulate CaMKII autophosphorylation. Mutations in human CASK have recently been shown to result in intellectual disability and neurological defects suggesting a role in plasticity and learning possibly via regulation of CaMKII autophosphorylation.
Collapse
Affiliation(s)
- Bilal R Malik
- School of Physiology and Pharmacology, University of Bristol Bristol, UK
| | - James J L Hodge
- School of Physiology and Pharmacology, University of Bristol Bristol, UK
| |
Collapse
|
13
|
Gillespie JM, Hodge JJL. CASK regulates CaMKII autophosphorylation in neuronal growth, calcium signaling, and learning. Front Mol Neurosci 2013; 6:27. [PMID: 24062638 PMCID: PMC3769642 DOI: 10.3389/fnmol.2013.00027] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 08/24/2013] [Indexed: 11/27/2022] Open
Abstract
Calcium (Ca2+)/calmodulin (CaM)-dependent kinase II (CaMKII) activity plays a fundamental role in learning and memory. A key feature of CaMKII in memory formation is its ability to be regulated by autophosphorylation, which switches its activity on and off during synaptic plasticity. The synaptic scaffolding protein CASK (calcium (Ca2+)/calmodulin (CaM) associated serine kinase) is also important for learning and memory, as mutations in CASK result in intellectual disability and neurological defects in humans. We show that in Drosophila larvae, CASK interacts with CaMKII to control neuronal growth and calcium signaling. Furthermore, deletion of the CaMK-like and L27 domains of CASK (CASK β null) or expression of overactive CaMKII (T287D) produced similar effects on synaptic growth and Ca2+ signaling. CASK overexpression rescues the effects of CaMKII overactivity, consistent with the notion that CASK and CaMKII act in a common pathway that controls these neuronal processes. The reduction in Ca2+ signaling observed in the CASK β null mutant caused a decrease in vesicle trafficking at synapses. In addition, the decrease in Ca2+ signaling in CASK mutants was associated with an increase in Ether-à-go-go (EAG) potassium (K+) channel localization to synapses. Reducing EAG restored the decrease in Ca2+ signaling observed in CASK mutants to the level of wildtype, suggesting that CASK regulates Ca2+ signaling via EAG. CASK knockdown reduced both appetitive associative learning and odor evoked Ca2+ responses in Drosophila mushroom bodies, which are the learning centers of Drosophila. Expression of human CASK in Drosophila rescued the effect of CASK deletion on the activity state of CaMKII, suggesting that human CASK may also regulate CaMKII autophosphorylation.
Collapse
Affiliation(s)
- John M Gillespie
- School of Physiology and Pharmacology, University of Bristol Bristol, UK
| | | |
Collapse
|
14
|
Malik BR, Gillespie JM, Hodge JJL. CASK and CaMKII function in the mushroom body α'/β' neurons during Drosophila memory formation. Front Neural Circuits 2013; 7:52. [PMID: 23543616 PMCID: PMC3608901 DOI: 10.3389/fncir.2013.00052] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 03/09/2013] [Indexed: 11/13/2022] Open
Abstract
Ca(2+)/CaM serine/threonine kinase II (CaMKII) is a central molecule in mechanisms of synaptic plasticity and memory. A vital feature of CaMKII in plasticity is its ability to switch to a calcium (Ca(2+)) independent constitutively active state after autophosphorylation at threonine 287 (T287). A second pair of sites, T306 T307 in the calmodulin (CaM) binding region once autophosphorylated, prevent subsequent CaM binding and inactivates the kinase during synaptic plasticity and memory. Recently a synaptic molecule called Ca(2+)/CaM-dependent serine protein kinase (CASK) has been shown to control both sets of CaMKII autophosphorylation events and hence is well poised to be a key regulator of memory. We show deletion of full length CASK or just its CaMK-like and L27 domains disrupts middle-term memory (MTM) and long-term memory (LTM), with CASK function in the α'/β' subset of mushroom body neurons being required for memory. Likewise directly changing the levels of CaMKII autophosphorylation in these neurons removed MTM and LTM. The requirement of CASK and CaMKII autophosphorylation was not developmental as their manipulation just in the adult α'/β' neurons was sufficient to remove memory. Overexpression of CASK or CaMKII in the α'/β' neurons also occluded MTM and LTM. Overexpression of either Drosophila or human CASK in the α'/β' neurons of the CASK mutant completely rescued memory, confirming that CASK signaling in α'/β' neurons is necessary and sufficient for Drosophila memory formation and that the neuronal function of CASK is conserved between Drosophila and human. At the cellular level CaMKII overexpression in the α'/β' neurons increased activity dependent Ca(2+) responses while reduction of CaMKII decreased it. Likewise reducing CASK or directly expressing a phosphomimetic CaMKII T287D transgene in the α'/β' similarly decreased Ca(2+) signaling. Our results are consistent with CASK regulating CaMKII autophosphorylation in a pathway required for memory formation that involves activity dependent changes in Ca(2+) signaling in the α'/β' neurons.
Collapse
Affiliation(s)
- Bilal R Malik
- School of Physiology and Pharmacology, University of Bristol Bristol, UK
| | | | | |
Collapse
|
15
|
Klug JR, Mathur BN, Kash TL, Wang HD, Matthews RT, Robison AJ, Anderson ME, Deutch AY, Lovinger DM, Colbran RJ, Winder DG. Genetic inhibition of CaMKII in dorsal striatal medium spiny neurons reduces functional excitatory synapses and enhances intrinsic excitability. PLoS One 2012; 7:e45323. [PMID: 23028932 PMCID: PMC3448631 DOI: 10.1371/journal.pone.0045323] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 08/15/2012] [Indexed: 11/18/2022] Open
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) is abundant in striatal medium spiny neurons (MSNs). CaMKII is dynamically regulated by changes in dopamine signaling, as occurs in Parkinson's disease as well as addiction. Although CaMKII has been extensively studied in the hippocampus where it regulates excitatory synaptic transmission, relatively little is known about how it modulates neuronal function in the striatum. Therefore, we examined the impact of selectively overexpressing an EGFP-fused CaMKII inhibitory peptide (EAC3I) in striatal medium spiny neurons (MSNs) using a novel transgenic mouse model. EAC3I-expressing cells exhibited markedly decreased excitatory transmission, indicated by a decrease in the frequency of spontaneous excitatory postsynaptic currents (sEPSCs). This decrease was not accompanied by changes in the probability of release, levels of glutamate at the synapse, or changes in dendritic spine density. CaMKII regulation of the AMPA receptor subunit GluA1 is a major means by which the kinase regulates neuronal function in the hippocampus. We found that the decrease in striatal excitatory transmission seen in the EAC3I mice is mimicked by deletion of GluA1. Further, while CaMKII inhibition decreased excitatory transmission onto MSNs, it increased their intrinsic excitability. These data suggest that CaMKII plays a critical role in setting the excitability rheostat of striatal MSNs by coordinating excitatory synaptic drive and the resulting depolarization response.
Collapse
Affiliation(s)
- Jason R. Klug
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Brian N. Mathur
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland, United States of America
| | - Thomas L. Kash
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Hui-Dong Wang
- Department of Psychiatry, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Robert T. Matthews
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- J.F. Kennedy Center for Research on Human Development, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - A. J. Robison
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Mark E. Anderson
- Departments of Internal Medicine and Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
| | - Ariel Y. Deutch
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- J.F. Kennedy Center for Research on Human Development, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Psychiatry, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - David M. Lovinger
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland, United States of America
| | - Roger J. Colbran
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- J.F. Kennedy Center for Research on Human Development, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Danny G. Winder
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- J.F. Kennedy Center for Research on Human Development, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail:
| |
Collapse
|
16
|
Johnson C, Chun-Jen Lin C, Stern M. Ras-dependent and Ras-independent effects of PI3K in Drosophila motor neurons. GENES BRAIN AND BEHAVIOR 2012; 11:848-58. [DOI: 10.1111/j.1601-183x.2012.00822.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 06/02/2012] [Accepted: 07/09/2012] [Indexed: 11/30/2022]
Affiliation(s)
- C. Johnson
- Department of Biochemistry and Cell Biology; Rice University; Houston; TX; USA
| | - C. Chun-Jen Lin
- Department of Biochemistry and Cell Biology; Rice University; Houston; TX; USA
| | - M. Stern
- Department of Biochemistry and Cell Biology; Rice University; Houston; TX; USA
| |
Collapse
|
17
|
Constitutive activation of Ca2+/calmodulin-dependent protein kinase II during development impairs central cholinergic transmission in a circuit underlying escape behavior in Drosophila. J Neurosci 2012; 32:170-82. [PMID: 22219280 DOI: 10.1523/jneurosci.6583-10.2012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Development of neural circuitry relies on precise matching between correct synaptic partners and appropriate synaptic strength tuning. Adaptive developmental adjustments may emerge from activity and calcium-dependent mechanisms. Calcium/calmodulin-dependent protein kinase II (CaMKII) has been associated with developmental synaptic plasticity, but its varied roles in different synapses and developmental stages make mechanistic generalizations difficult. In contrast, we focused on synaptic development roles of CaMKII in a defined sensory-motor circuit. Thus, different forms of CaMKII were expressed with UAS-Gal4 in distinct components of the giant fiber system, the escape circuit of Drosophila, consisting of photoreceptors, interneurons, motoneurons, and muscles. The results demonstrate that the constitutively active CaMKII-T287D impairs development of cholinergic synapses in giant fiber dendrites and thoracic motoneurons, preventing light-induced escape behavior. The locus of the defects is postsynaptic as demonstrated by selective expression of transgenes in distinct components of the circuit. Furthermore, defects among these cholinergic synapses varied in severity, while the glutamatergic neuromuscular junctions appeared unaffected, demonstrating differential effects of CaMKII misregulation on distinct synapses of the same circuit. Limiting transgene expression to adult circuits had no effects, supporting the role of misregulated kinase activity in the development of the system rather than in acutely mediating escape responses. Overexpression of wild-type transgenes did not affect circuit development and function, suggesting but not proving that the CaMKII-T287D effects are not due to ectopic expression. Therefore, regulated CaMKII autophosphorylation appears essential in central synapse development, and particular cholinergic synapses are affected differentially, although they operate via the same nicotinic receptor.
Collapse
|
18
|
Liang R, Liu X, Wei L, Wang W, Zheng P, Yan X, Zhao Y, Liu L, Cao X. The modulation of the excitability of primary sensory neurons by Ca2+–CaM–CaMKII pathway. Neurol Sci 2011; 33:1083-93. [DOI: 10.1007/s10072-011-0907-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/14/2011] [Indexed: 01/19/2023]
|
19
|
Chorna T, Hasan G. The genetics of calcium signaling in Drosophila melanogaster. Biochim Biophys Acta Gen Subj 2011; 1820:1269-82. [PMID: 22100727 DOI: 10.1016/j.bbagen.2011.11.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 10/31/2011] [Accepted: 11/02/2011] [Indexed: 01/13/2023]
Abstract
BACKGROUND Genetic screens for behavioral and physiological defects in Drosophila melanogaster, helped identify several components of calcium signaling of which some, like the Trps, were novel. For genes initially identified in vertebrates, reverse genetic methods have allowed functional studies at the cellular and systemic levels. SCOPE OF REVIEW The aim of this review is to explain how various genetic methods available in Drosophila have been used to place different arms of Ca2+ signaling in the context of organismal development, physiology and behavior. MAJOR CONCLUSION Mutants generated in genes encoding a range of Ca2+ transport systems, binding proteins and enzymes affect multiple aspects of neuronal and muscle physiology. Some also affect the maintenance of ionic balance and excretion from malpighian tubules and innate immune responses in macrophages. Aspects of neuronal physiology affected include synaptic growth and plasticity, sensory transduction, flight circuit development and function. Genetic interaction screens have shown that mechanisms of maintaining Ca2+ homeostasis in Drosophila are cell specific and require a synergistic interplay between different intracellular and plasma membrane Ca2+ signaling molecules. GENERAL SIGNIFICANCE Insights gained through genetic studies of conserved Ca2+ signaling pathways have helped understand multiple aspects of fly physiology. The similarities between mutant phenotypes of Ca2+ signaling genes in Drosophila with certain human disease conditions, especially where homologous genes are causative factors, are likely to aid in the discovery of underlying disease mechanisms and help develop novel therapeutic strategies. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signalling.
Collapse
Affiliation(s)
- Tetyana Chorna
- National Center for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, India
| | | |
Collapse
|
20
|
The metabotropic glutamate receptor activates the lipid kinase PI3K in Drosophila motor neurons through the calcium/calmodulin-dependent protein kinase II and the nonreceptor tyrosine protein kinase DFak. Genetics 2011; 188:601-13. [PMID: 21515581 DOI: 10.1534/genetics.111.128561] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Ligand activation of the metabotropic glutamate receptor (mGluR) activates the lipid kinase PI3K in both the mammalian central nervous system and Drosophila motor nerve terminal. In several subregions of the mammalian brain, mGluR-mediated PI3K activation is essential for a form of synaptic plasticity termed long-term depression (LTD), which is implicated in neurological diseases such as fragile X and autism. In Drosophila larval motor neurons, ligand activation of DmGluRA, the sole Drosophila mGluR, similarly mediates a PI3K-dependent downregulation of neuronal activity. The mechanism by which mGluR activates PI3K remains incompletely understood in either mammals or Drosophila. Here we identify CaMKII and the nonreceptor tyrosine kinase DFak as critical intermediates in the DmGluRA-dependent activation of PI3K at Drosophila motor nerve terminals. We find that transgene-induced CaMKII inhibition or the DFak(CG1) null mutation each block the ability of glutamate application to activate PI3K in larval motor nerve terminals, whereas transgene-induced CaMKII activation increases PI3K activity in motor nerve terminals in a DFak-dependent manner, even in the absence of glutamate application. We also find that CaMKII activation induces other PI3K-dependent effects, such as increased motor axon diameter and increased synapse number at the larval neuromuscular junction. CaMKII, but not PI3K, requires DFak activity for these increases. We conclude that the activation of PI3K by DmGluRA is mediated by CaMKII and DFak.
Collapse
|
21
|
Lavialle-Defaix C, Moignot B, Legros C, Lapied B. How Does Calcium-Dependent Intracellular Regulation of Voltage-Dependent Sodium Current Increase the Sensitivity to the Oxadiazine Insecticide Indoxacarb Metabolite Decarbomethoxylated JW062 (DCJW) in Insect Pacemaker Neurons? J Pharmacol Exp Ther 2010; 333:264-72. [DOI: 10.1124/jpet.109.163519] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
22
|
Hodge JJL. Ion channels to inactivate neurons in Drosophila. Front Mol Neurosci 2009; 2:13. [PMID: 19750193 PMCID: PMC2741205 DOI: 10.3389/neuro.02.013.2009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Accepted: 08/11/2009] [Indexed: 02/05/2023] Open
Abstract
Ion channels are the determinants of excitability; therefore, manipulation of their levels and properties provides an opportunity for the investigator to modulate neuronal and circuit function. There are a number of ways to suppress electrical activity in Drosophila neurons, for instance, over-expression of potassium channels (i.e. Shaker Kv1, Shaw Kv3, Kir2.1 and DORK) that are open at resting membrane potential. This will result in increased potassium efflux and membrane hyperpolarisation setting resting membrane potential below the threshold required to fire action potentials. Alternatively over-expression of other channels, pumps or co-transporters that result in a hyperpolarised membrane potential will also prevent firing. Lastly, neurons can be inactivated by, disrupting or reducing the level of functional voltage-gated sodium (Nav1 paralytic) or calcium (Cav2 cacophony) channels that mediate the depolarisation phase of action potentials. Similarly, strategies involving the opposite channel manipulation should allow net depolarisation and hyperexcitation in a given neuron. These changes in ion channel expression can be brought about by the versatile transgenic (i.e. Gal4/UAS based) systems available in Drosophila allowing fine temporal and spatial control of (channel) transgene expression. These systems are making it possible to electrically inactivate (or hyperexcite) any neuron or neural circuit in the fly brain, and much like an exquisite lesion experiment, potentially elucidate whatever interesting behaviour or phenotype each network mediates. These techniques are now being used in Drosophila to reprogram electrical activity of well-defined circuits and bring about robust and easily quantifiable changes in behaviour, allowing different models and hypotheses to be rapidly tested.
Collapse
Affiliation(s)
- James J L Hodge
- Physiology and Pharmacology Department, University of Bristol Bristol, UK
| |
Collapse
|
23
|
Lee HG, Rohila S, Han KA. The octopamine receptor OAMB mediates ovulation via Ca2+/calmodulin-dependent protein kinase II in the Drosophila oviduct epithelium. PLoS One 2009; 4:e4716. [PMID: 19262750 PMCID: PMC2650798 DOI: 10.1371/journal.pone.0004716] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 02/04/2009] [Indexed: 11/18/2022] Open
Abstract
Ovulation is an essential physiological process in sexual reproduction; however, the underlying cellular mechanisms are poorly understood. We have previously shown that OAMB, a Drosophila G-protein-coupled receptor for octopamine (the insect counterpart of mammalian norepinephrine), is required for ovulation induced upon mating. OAMB is expressed in the nervous and reproductive systems and has two isoforms (OAMB-AS and OAMB-K3) with distinct capacities to increase intracellular Ca2+ or intracellular Ca2+ and cAMP in vitro. Here, we investigated tissue specificity and intracellular signals required for OAMB's function in ovulation. Restricted OAMB expression in the adult oviduct epithelium, but not the nervous system, reinstated ovulation in oamb mutant females, in which either OAMB isoform was sufficient for the rescue. Consistently, strong immunoreactivities for both isoforms were observed in the wild-type oviduct epithelium. To delineate the cellular mechanism by which OAMB regulates ovulation, we explored protein kinases functionally interacting with OAMB by employing a new GAL4 driver with restricted expression in the oviduct epithelium. Conditional inhibition of Ca2+/Calmodulin-dependent protein kinase II (CaMKII), but not protein kinase A or C, in the oviduct epithelium inhibited ovulation. Moreover, constitutively active CaMKII, but not protein kinase A, expressed only in the adult oviduct epithelium fully rescued the oamb female's phenotype, demonstrating CaMKII as a major downstream molecule conveying the OAMB's ovulation signal. This is consistent with the ability of both OAMB isoforms, whose common intracellular signal in vitro is Ca2+, to reinstate ovulation in oamb females. These observations reveal the critical roles of the oviduct epithelium and its cellular components OAMB and CaMKII in ovulation. It is conceivable that the OAMB-mediated cellular activities stimulated upon mating are crucial for secretory activities suitable for egg transfer from the ovary to the uterus.
Collapse
Affiliation(s)
- Hyun-Gwan Lee
- The Huck Institute Genetics Graduate Program, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Suman Rohila
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Kyung-An Han
- The Huck Institute Genetics Graduate Program, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
| |
Collapse
|
24
|
Sun XX, Bostrom SL, Griffith LC. Alternative splicing of the eag potassium channel gene in Drosophila generates a novel signal transduction scaffolding protein. Mol Cell Neurosci 2008; 40:338-43. [PMID: 19130887 DOI: 10.1016/j.mcn.2008.11.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2008] [Revised: 11/08/2008] [Accepted: 11/21/2008] [Indexed: 01/24/2023] Open
Abstract
The Drosophila eag gene has been shown to regulate neuronal excitability, olfaction, associative learning and larval locomotion. Not all of the roles of this gene in these processes can be explained by its function as a voltage-gated potassium channel. In this study, we show that the eag gene is spliced in a PKA- and PKC-regulated manner to produce a protein lacking channel domains. This protein, in the context of activated PKA, can engage cellular signaling pathways that alter cell structure. Nuclear localization is necessary for C-terminal-mediated effects, which also require MAPK. The requirement for PKA/PKC activation in the synthesis and function of this novel protein suggests that it may couple membrane events to nuclear signaling to regulate neuronal function on long time scales.
Collapse
Affiliation(s)
- Xiu Xia Sun
- Department of Biology, National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454-9110, USA
| | | | | |
Collapse
|
25
|
Liu CH, Satoh AK, Postma M, Huang J, Ready DF, Hardie RC. Ca2+-dependent metarhodopsin inactivation mediated by calmodulin and NINAC myosin III. Neuron 2008; 59:778-89. [PMID: 18786361 DOI: 10.1016/j.neuron.2008.07.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Revised: 06/03/2008] [Accepted: 07/09/2008] [Indexed: 10/21/2022]
Abstract
Phototransduction in flies is the fastest known G protein-coupled signaling cascade, but how this performance is achieved remains unclear. Here, we investigate the mechanism and role of rhodopsin inactivation. We determined the lifetime of activated rhodopsin (metarhodopsin = M( *)) in whole-cell recordings from Drosophila photoreceptors by measuring the time window within which inactivating M( *) by photoreisomerization to rhodopsin could suppress responses to prior illumination. M( *) was inactivated rapidly (tau approximately 20 ms) under control conditions, but approximately 10-fold more slowly in Ca2+-free solutions. This pronounced Ca2+ dependence of M( *) inactivation was unaffected by mutations affecting phosphorylation of rhodopsin or arrestin but was abolished in mutants of calmodulin (CaM) or the CaM-binding myosin III, NINAC. This suggests a mechanism whereby Ca2+ influx acting via CaM and NINAC accelerates the binding of arrestin to M( *). Our results indicate that this strategy promotes quantum efficiency, temporal resolution, and fidelity of visual signaling.
Collapse
Affiliation(s)
- Che-Hsiung Liu
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge CB23DY, UK
| | | | | | | | | | | |
Collapse
|
26
|
Lee J, Ueda A, Wu CF. Pre- and post-synaptic mechanisms of synaptic strength homeostasis revealed by slowpoke and shaker K+ channel mutations in Drosophila. Neuroscience 2008; 154:1283-96. [PMID: 18539401 DOI: 10.1016/j.neuroscience.2008.04.043] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Revised: 04/11/2008] [Accepted: 04/15/2008] [Indexed: 11/24/2022]
Abstract
We report naturally occurring, systematic variations in synaptic strength at neuromuscular junctions along the dorsal-ventral (D-V) axis of the Drosophila larval body wall. These gradual changes were correlated with differences in presynaptic neurotransmitter release regulated by nerve terminal excitability and in postsynaptic receptor composition influencing miniature excitatory junctional potential (mEJP) amplitude. Surprisingly, synaptic strength and D-V differentials at physiological Ca(2+) levels were not significantly altered in slowpoke (slo) and Shaker (Sh) mutants, despite their defects in two major repolarizing forces, Ca(2+)-activated Slo (BK) and voltage-activated Sh currents, respectively. However, lowering [Ca(2+)](o) levels revealed greatly altered synaptic mechanisms in these mutants, indicated by drastically enhanced excitatory junctional potentials (EJPs) in Sh but paradoxically reduced EJPs in slo. Removal of Sh current in slo mutants by 4-aminopyridine blockade or by combining slo with Sh mutations led to strikingly increased synaptic transmission, suggesting upregulation of presynaptic Sh current to limit excessive neurotransmitter release in the absence of Slo current. In addition, slo mutants displayed altered immunoreactivity intensity ratio between DGluRIIA and DGluRIIB receptor subunits. This modified receptor composition caused smaller mEJP amplitudes, further preventing excessive transmission in the absence of Slo current. Such compensatory regulations were prevented by rutabaga (rut) adenylyl cyclase mutations in rut slo double mutants, demonstrating a novel role of rut in homeostatic plasticity, in addition to its well-established function in learning behavior.
Collapse
Affiliation(s)
- J Lee
- Interdisciplinary Program in Neuroscience, University of Iowa, Iowa City, IA 52242, USA
| | | | | |
Collapse
|
27
|
Liu Q, Chen B, Ge Q, Wang ZW. Presynaptic Ca2+/calmodulin-dependent protein kinase II modulates neurotransmitter release by activating BK channels at Caenorhabditis elegans neuromuscular junction. J Neurosci 2007; 27:10404-13. [PMID: 17898212 PMCID: PMC6673169 DOI: 10.1523/jneurosci.5634-06.2007] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Although Ca2+/calmodulin-dependent protein kinase II (CaMKII) is enriched at the presynaptic nerve terminal, its role in neurotransmitter release is poorly defined. We assessed the function of presynaptic CaMKII in neurotransmitter release and tested the hypothesis that BK channel is a mediator of presynaptic CaMKII function by analyzing miniature and evoked postsynaptic currents at the Caenorhabditis elegans neuromuscular junction. Both loss-of-function (lf) and gain-of-function (gf) of unc-43, the gene encoding CaMKII, inhibited neurotransmitter release. The inhibitory effect of unc-43(gf) was reversed by mutation or blockade of the BK channel SLO-1. SLO-1 expressed in Xenopus oocytes could be activated by recombinant rat alpha-CaMKII, and this effect of CaMKII was abolished by mutating a threonine residue (T425) at a consensus CaMKII phosphorylation site in the first RCK (regulator of conductance for K+) domain of the channel. Expression of slo-1(T425A) in neurons antagonized the inhibitory effect of unc-43(gf) on neurotransmitter release as slo-1(lf) did. The inhibitory effect of unc-43(gf) was not reversed by unc-103(lf), dgk-1(lf), or eat-16(lf), which reportedly suppress behavioral phenotypes of unc-43(gf). These observations suggest that presynaptic CaMKII is a bidirectional modulator of neurotransmitter release, presumably by phosphorylating different molecular targets, and that its negative modulatory effect on the release is mainly mediated by SLO-1 activation.
Collapse
Affiliation(s)
- Qiang Liu
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Bojun Chen
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Qian Ge
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030
| |
Collapse
|
28
|
Wiltgen BJ, Law M, Ostlund S, Mayford M, Balleine BW. The influence of Pavlovian cues on instrumental performance is mediated by CaMKII activity in the striatum. Eur J Neurosci 2007; 25:2491-7. [PMID: 17445244 DOI: 10.1111/j.1460-9568.2007.05487.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pavlovian cues associated with reward exert a powerful motivational influence on the performance of goal-directed actions. This motivational process depends critically on the ventral striatum, although little is known about the cellular and molecular mechanisms that mediate it. In the current experiments we examined the role of calcium calmodulin-dependent kinase II (CaMKII) by using transgenic mice that express a constitutively active form of this kinase. We found that controlled expression of active CaMKII in the striatum did not affect learning but did impair the motivation of goal-directed actions by Pavlovian cues associated with reward. Mutant mice learned to lever press for reward, remained sensitive to outcome devaluation and contingency degradation manipulations, and were able to acquire Pavlovian responses to cues paired with reward. However, Pavlovian cues were completely unable to motivate lever pressing in mutant mice. This was true even in mice trained with the CaMKII transgene turned off and then tested with it turned on. We were also able to suppress transgene expression in impaired mutants and fully restore the motivational effects of reward cues in these animals. Therefore, the current experiments demonstrate that normal CaMKII activity in the striatum is essential for the motivational effects of reward cues on goal-directed actions.
Collapse
Affiliation(s)
- Brian J Wiltgen
- Department of Psychology and the Brain Research Institute, University of California, Los Angeles, CA 90095, USA
| | | | | | | | | |
Collapse
|
29
|
Chen L, Bohanick JD, Nishihara M, Seamans JK, Yang CR. Dopamine D1/5 receptor-mediated long-term potentiation of intrinsic excitability in rat prefrontal cortical neurons: Ca2+-dependent intracellular signaling. J Neurophysiol 2007; 97:2448-64. [PMID: 17229830 DOI: 10.1152/jn.00317.2006] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Prefrontal cortex (PFC) dopamine D1/5 receptors modulate long- and short-term neuronal plasticity that may contribute to cognitive functions. Synergistic to synaptic strength modulation, direct postsynaptic D1/5 receptor activation also modulates voltage-dependent ionic currents that regulate spike firing, thus altering the neuronal input-output relationships in a process called long-term potentiation of intrinsic excitability (LTP-IE). Here, the intracellular signals that mediate this D1/5 receptor-dependent LTP-IE were determined using whole cell current-clamp recordings in layer V/VI rat pyramidal neurons from PFC slices. After blockade of all major amino acid receptors (V(hold) = -65 mV) brief tetanic stimulation (20 Hz) of local afferents or application of the D1 agonist SKF81297 (0.2-50 microM) induced LTP-IE, as shown by a prolonged (>40 min) increase in depolarizing pulse-evoked spike firing. Pretreatment with the D1/5 antagonist SCH23390 (1 microM) blocked both the tetani- and D1/5 agonist-induced LTP-IE, suggesting a D1/5 receptor-mediated mechanism. The SKF81297-induced LTP-IE was significantly attenuated by Cd(2+), [Ca(2+)](i) chelation, by inhibition of phospholipase C, protein kinase-C, and Ca(2+)/calmodulin kinase-II, but not by inhibition of adenylate cyclase, protein kinase-A, MAP kinase, or L-type Ca(2+) channels. Thus this form of D1/5 receptor-mediated LTP-IE relied on Ca(2+) influx via non-L-type Ca(2+) channels, activation of PLC, intracellular Ca(2+) elevation, activation of Ca(2+)-dependent CaMKII, and PKC to mediate modulation of voltage-dependent ion channel(s). This D1/5 receptor-mediated modulation by PKC coexists with the previously described PKA-dependent modulation of K(+) and Ca(2+) currents to dynamically regulate overall excitability of PFC neurons.
Collapse
Affiliation(s)
- Long Chen
- National Standard Lab of Pharmacology for Chinese Materia Medica, Research Center of Acupuncture and Pharmacology, Nanjing University of Traditional Chinese Medicine, Nanjing, China
| | | | | | | | | |
Collapse
|
30
|
Abstract
Behavioral and genetic studies in Drosophila have contributed to our understanding of molecular mechanisms that underlie the complex processes of learning and memory. Use of this model organism for exploration of the cellular mechanisms of memory formation requires the ability to monitor synaptic activity in the underlying neural networks, a challenging task in the tiny adult fly. Here, we describe an isolated whole-brain preparation in which it is possible to obtain in situ whole-cell recordings from adult Kenyon cells, key members of a neural circuit essential for olfactory associative learning in Drosophila. The presence of sodium action potential (AP)-dependent synaptic potentials and synaptic currents in >50% of the Kenyon cells shows that these neurons are members of a spontaneously active neural circuit in the isolated brain. The majority of sodium AP-dependent synaptic transmission is blocked by curare and by alpha-bungarotoxin (alpha-BTX). This demonstrates that nicotinic acetylcholine receptors (nAChRs) are responsible for most of the spontaneous excitatory drive in this circuit in the absence of normal sensory input. Furthermore, analysis of sodium AP-independent synaptic currents provides the first direct demonstration that alpha-BTX-sensitive nAChRs mediate fast excitatory synaptic transmission in Kenyon cells in the adult Drosophila brain. This new preparation, in which whole-cell recordings and pharmacology can be combined with genetic approaches, will be critical in understanding the contribution of nAChR-mediated fast synaptic transmission to cellular plasticity in the neural circuits underlying olfactory associative learning.
Collapse
Affiliation(s)
- Huaiyu Gu
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697-1280, USA
| | | |
Collapse
|
31
|
Griffith LC, Budnik V. Plasticity and second messengers during synapse development. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2006; 75:237-65. [PMID: 17137931 PMCID: PMC4664443 DOI: 10.1016/s0074-7742(06)75011-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Effective function of the locomotor system in the Drosophila larva requires a continuous adjustment of synaptic architecture and neurotransmission at the neuromuscular junction (NMJ). This feature has made the larval NMJ a favorite model to study the genetic and molecular mechanisms underlying synapse plasticity. This chapter will review experimental strategies used to study plasticity at the NMJ, the cellular parameters affected during plastic changes, and many of the known molecules involved in plastic changes. In addition, signal transduction pathways activated during plasticity will be discussed.
Collapse
Affiliation(s)
- Leslie C. Griffith
- Dept of Biology and National Center for Behavioral Genomics, Brandeis University, 415 South St., Waltham, MA, 02454, USA
- Corresponding Author: phone: 781 736 3125, FAX: 781 736 3107,
| | - Vivian Budnik
- Department of Neurobiology, University of Massachusetts Medical School, Aaron Lazare Medical Research Building, 364 Plantation Street Worcester, MA 01605-2324, USA
| |
Collapse
|
32
|
Hodge JJL, Choi JC, O'Kane CJ, Griffith LC. Shaw potassium channel genes in Drosophila. ACTA ACUST UNITED AC 2005; 63:235-54. [PMID: 15751025 DOI: 10.1002/neu.20126] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Drosophila Shaw encodes a voltage-insensitive, slowly activating, noninactivating K(+) current. The functional and developmental roles of this channel are unknown. In this study, we use a dominant transgenic strategy to investigate Shaw function and describe a second member of the Shaw family, Shawl. In situ hybridization showed that the two Shaw family genes, Shaw and Shawl, have largely nonoverlapping expression patterns in embryos. Shaw is expressed mainly in excitable cells of the CNS and PNS of late embryos. Shawl is expressed in many nonexcitable cell types: ubiquitously in embryos until the germband extends, then transiently in the developing CNS and PNS, becoming restricted to progressively smaller subsets of the CNS. Ectopic full-length and truncated Shaw localize differently within neurons, and produce uneclosed small pupae and adults with unfurled wings and softened cuticle. This phenotype was mapped to the crustacean cardioactive peptide (CCAP)-neuropeptide circuit. Widespread expression of Shaw in the nervous system results in a reduction in body mass, ether-induced shaking, and lethality. Expression of full-length Shaw had more extreme phenotypic consequences and caused earlier lethality than expression of truncated Shaw in a given GAL4 pattern. Whole cell recordings from ventral ganglion motor neurons expressing the truncated Shaw protein suggest that a major role of Shaw channels in these cells is to contribute to the resting potential.
Collapse
Affiliation(s)
- James J L Hodge
- Department of Genetics, University of Cambridge, Downing Site, Cambridge CB2 3EH, UK
| | | | | | | |
Collapse
|
33
|
Mehren JE, Griffith LC. Calcium-independent calcium/calmodulin-dependent protein kinase II in the adult Drosophila CNS enhances the training of pheromonal cues. J Neurosci 2005; 24:10584-93. [PMID: 15564574 PMCID: PMC6730130 DOI: 10.1523/jneurosci.3560-04.2004] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) is abundant in the CNS and is crucial for cellular and behavioral plasticity. It is thought that the ability of CaMKII to autophosphorylate and become Ca2+ independent allows it to act as a molecular memory switch. We have shown previously that inhibition of Drosophila CaMKII leads to impaired performance in the courtship conditioning associative memory assay, but it was unknown whether the constitutive form of the kinase had a special role in learning. In this study, we use a tripartite transgenic system combining GAL4/UAS with the tetracycline-off system to spatially and temporally manipulate levels of Ca2+-independent CaMKII activity in Drosophila. We find an enhancement of information processing during the training period with Ca2+-independent, but not Ca2+-dependent, CaMKII. During training, control animals have a lag before active suppression of courtship begins. Animals expressing Ca2+-independent CaMKII have no lag, implying that there is a threshold level of Ca2+-independent activity that must be present to suppress courtship. This is the first demonstration, in any organism, of enhanced behavioral plasticity with overexpression of constitutively active CaMKII. Anatomical studies indicate that transgene expression in antennal lobes and extrinsic mushroom body neurons drives this behavioral enhancement. Interestingly, immediate memory was unaffected by expression of T287D CaMKII in mushroom bodies, although previous studies have shown that CaMKII activity is required in this brain region for memory formation. These results suggest that the biochemical mechanisms of CaMKII-dependent memory formation are threshold based in only a subset of neurons.
Collapse
Affiliation(s)
- Jennifer E Mehren
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454-9110, USA
| | | |
Collapse
|
34
|
Elgersma Y, Sweatt JD, Giese KP. Mouse genetic approaches to investigating calcium/calmodulin-dependent protein kinase II function in plasticity and cognition. J Neurosci 2005; 24:8410-5. [PMID: 15456813 PMCID: PMC6729904 DOI: 10.1523/jneurosci.3622-04.2004] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Ype Elgersma
- Department of Neuroscience, Erasmus Medical Center, 3000 DR, Rotterdam, The Netherlands.
| | | | | |
Collapse
|
35
|
Morimoto-Tanifuji T, Kazama H, Nose A. Developmental stage-dependent modulation of synapses by postsynaptic expression of activated calcium/calmodulin-dependent protein kinase II. Neuroscience 2005; 128:797-806. [PMID: 15464287 DOI: 10.1016/j.neuroscience.2004.07.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/13/2004] [Indexed: 11/25/2022]
Abstract
In Drosophila neuromuscular junctions, there is a unique system which consists of two neighboring muscles (M6 and M7) innervated by the same neurons and a gene of interest can be expressed in only M6 or in both muscles by GAL4-upstream activating sequence expression system. By using this system, we previously demonstrated that expression of activated calcium/calmodulin-dependent protein kinase II (CaMKII) in the muscle cell promotes coordinated maturation of pre- and postsynaptic sites of larvae just after hatching (JAH larvae) in a synapse-specific manner. Here we show that the promotive effects are no longer seen in the older larvae, 8-10 h after hatching (8 h AH larvae). Morphological studies indicate that CaMKII activation in fact reduces postsynaptic sites at 8 h AH. This is opposite to the effect observed in JAH larvae. These results suggest that the mode of CaMKII function switches during development, and that regulation of postsynaptic CaMKII activity is necessary for normal synaptic development. Finally, we report that in 8 h AH but not in JAH larvae, synapses on M7, in which CaMKII activity is not manipulated, are affected by the expression of activated CaMKII in M6. This suggests the interesting possibility that at certain developmental stages only, modification of synapses on one target cell can influence the synapses on another target cell innervated by the same neurons.
Collapse
Affiliation(s)
- T Morimoto-Tanifuji
- Department of Physics, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyoku, Tokyo 113-0033, Japan
| | | | | |
Collapse
|
36
|
Tsui J, Inagaki M, Schulman H. Calcium/calmodulin-dependent protein kinase II (CaMKII) localization acts in concert with substrate targeting to create spatial restriction for phosphorylation. J Biol Chem 2004; 280:9210-6. [PMID: 15582994 DOI: 10.1074/jbc.m407653200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) acts in diverse cell types by phosphorylating proteins with key calcium-dependent functions such as synaptic plasticity, electrical excitability, and neurotransmitter synthesis. CaMKII displays calcium-dependent binding to proteins in vitro and translocation to synaptic sites after glutamatergic activity in neurons. We therefore hypothesized that subcellular targeting of CaMKII can direct its substrate specificity in an activity-dependent fashion. Here, we examined whether activity-dependent colocalization of CaMKII and its substrates could result in regulation of substrate phosphorylation in cells. We find that substrates localized at cellular membranes required CaMKII translocation to these compartments to achieve effective phosphorylation. Spatial barriers to phosphorylation could be overcome by translocation and anchoring to the substrate itself or to nearby target proteins within the membrane compartment. In contrast, phosphorylation of a cytoplasmic counterpart of the substrate does not require CaMKII translocation or stable protein-protein binding. Cytosolic phosphorylation is more permissive, exhibiting partial calcium-independence. Localization-dependent substrate specificity can also show more graded levels of regulation within signaling microdomains. We find that colocalization of translocated CaMKII and its substrate to lipid rafts in the plasma membrane can modulate the magnitude of phosphorylation. Thus, dynamic regulation of both substrate and kinase localization provides a powerful and nuanced way to regulate CaMKII signal specificity.
Collapse
Affiliation(s)
- Jennifer Tsui
- Neurosciences Program, Stanford University School of Medicine, Stanford, California 94304, USA
| | | | | |
Collapse
|
37
|
Sun XX, Hodge JJL, Zhou Y, Nguyen M, Griffith LC. The eag Potassium Channel Binds and Locally Activates Calcium/Calmodulin-dependent Protein Kinase II. J Biol Chem 2004; 279:10206-14. [PMID: 14699099 DOI: 10.1074/jbc.m310728200] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) has been implicated in the regulation of neuronal excitability in many systems. Recent studies suggest that local regulation of membrane potential can have important computational consequences for neuronal function. In Drosophila, CaMKII regulates the eag potassium channel, but if and how this regulation was spatially restricted was unknown. Using coimmunoprecipitation from head extracts and in vitro binding assays, we show that CaMKII and Eag form a stable complex and that association with Eag activates CaMKII independently of CaM and autophosphorylation. Ca(2+)/CaM is necessary to initiate binding of CaMKII to Eag but not to sustain association because binding persists when CaM is removed. The Eag CaMKII-binding domain has homology to the CaMKII autoregulatory region, and the constitutively active CaMKII mutant, T287D, binds Eag Ca(2+)-independently in vitro and in vivo. These results favor a model in which the CaMKII-binding domain of Eag displaces the CaMKII autoinhibitory region. Displacement results in autophosphorylation-independent activation of CaMKII which persists even when Ca(2+) levels have gone down. Activity-dependent binding to this potassium channel substrate allows CaMKII to remain locally active even when Ca(2+) levels have dropped, providing a novel mechanism by which CaMKII can regulate excitability locally over long time scales.
Collapse
Affiliation(s)
- Xiu Xia Sun
- Department of Biology and Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02454-9110, USA
| | | | | | | | | |
Collapse
|
38
|
Lu CS, Hodge JJL, Mehren J, Sun XX, Griffith LC. Regulation of the Ca2+/CaM-responsive pool of CaMKII by scaffold-dependent autophosphorylation. Neuron 2004; 40:1185-97. [PMID: 14687552 DOI: 10.1016/s0896-6273(03)00786-4] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
CaMKII is critical for structural and functional plasticity. Here we show that Camguk (Cmg), the Drosophila homolog of CASK/Lin-2, associates in an ATP-regulated manner with CaMKII to catalyze formation of a pool of calcium-insensitive CaMKII. In the presence of Ca(2+)/CaM, CaMKII complexed to Cmg can autophosphorylate at T287 and become constitutively active. In the absence of Ca(2+)/CaM, ATP hydrolysis results in phosphorylation of T306 and inactivation of CaMKII. Cmg coexpression suppresses CaMKII activity in transfected cells, and the level of Cmg expression in Drosophila modulates postsynaptic T306 phosphorylation. These results suggest that Cmg, in the presence of Ca(2+)/CaM, can provide a localized source of active kinase. When Ca(2+)/CaM or synaptic activity is low, Cmg promotes inactivating autophosphorylation, producing CaMKII that requires phosphatase to reactivate. This interaction provides a mechanism by which the active postsynaptic pool of CaMKII can be controlled locally to differentiate active and inactive synapses.
Collapse
Affiliation(s)
- Cecilia S Lu
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02454, USA
| | | | | | | | | |
Collapse
|