151
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Frequency-dependent modes of synaptic vesicle endocytosis and exocytosis at adult mouse neuromuscular junctions. J Neurosci 2011; 31:1093-105. [PMID: 21248134 DOI: 10.1523/jneurosci.2800-10.2011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
During locomotion, adult rodent lumbar motoneurons fire in high-frequency (80-100 Hz) 1-2 s bursts every several seconds, releasing between 10,000 and 20,000 vesicles per burst. The estimated total vesicle pool size indicates that all vesicles would be used within 30 s; thus, a mechanism for rapid endocytosis and vesicle recycling is necessary to maintain effective transmission and motor behavior. However, whether such rapid recycling exists at mouse neuromuscular junctions (NMJs) or how it is regulated has been unclear. Here, we show that much less FM1-43 dye is lost per stimulus with 100 Hz stimulation than with 10 Hz stimulation even when the same number of vesicles undergo exocytosis. Electrophysiological data using folimycin show this lesser amount of dye loss is caused in part by the rapid reuse of vesicles. We showed previously that a myosin light chain kinase (MLCK)-myosin II pathway was required for effective transmission at 100 Hz. Here, we confirm the activation of MLCK, based on increased nerve terminal phospho-MLC immunostaining, with 100 Hz but not with 10 Hz stimulation. We further demonstrate that activation of MLCK, by increased extracellular Ca(2+), by PKC (protein kinase C) activation, or by a MLCK agonist peptide, reduces the amount of dye lost even with 10 Hz stimulation. MLCK activation at 10 Hz also resulted in more vesicles being rapidly reused. Thus, MLCK activation by 100 Hz stimulation switches the mechanism of vesicle cycling to a rapid-reuse mode and is required to sustain effective transmission in adult mouse NMJs.
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152
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Hyde R, Corkins ME, Somers GA, Hart AC. PKC-1 acts with the ERK MAPK signaling pathway to regulate Caenorhabditis elegans mechanosensory response. GENES BRAIN AND BEHAVIOR 2011; 10:286-98. [PMID: 21143768 DOI: 10.1111/j.1601-183x.2010.00667.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In most animals, multiple genes encode protein kinase C (PKC) proteins. Pharmacological studies have revealed numerous roles for this protein family, yet the in vivo roles of specific PKC proteins and the functional targets of PKC activation are poorly understood. We find that in Caenorhabditis elegans, two PKC genes, pkc-1 and tpa-1, are required for mechanosensory response; the role of the nPKCε/η ortholog, pkc-1, was examined in detail. pkc-1 function is required for response to nose touch in adult C. elegans and pkc-1 likely acts in the interneurons that regulate locomotion which are direct synaptic targets of mechanosensory neurons. Previous studies have suggested numerous possible targets of pkc-1; our analysis indicates that pkc-1 may act via the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) pathway. We find that ERK/MAPK pathway function is required for mechanosensory response in C. elegans and that at least one component of this pathway, lin-45 Raf, acts in interneurons of the mechanosensory circuit. Genetic analysis indicates that lin-45 and pkc-1 act together to regulate nose touch response. Thus, these results functionally link two conserved signaling pathways in adult C. elegans neurons and define distinct roles for PKC genes in vivo.
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Affiliation(s)
- R Hyde
- Massachusetts General Hospital, Center for Cancer Research, Charlestown, MA, USA
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153
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Lindsay TH, Thiele TR, Lockery SR. Optogenetic analysis of synaptic transmission in the central nervous system of the nematode Caenorhabditis elegans. Nat Commun 2011; 2:306. [PMID: 21556060 PMCID: PMC3935721 DOI: 10.1038/ncomms1304] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Accepted: 04/06/2011] [Indexed: 02/06/2023] Open
Abstract
A reliable method for recording evoked synaptic events in identified neurons in Caenorhabditis elegans would greatly accelerate our understanding of its nervous system at the molecular, cellular and network levels. Here we describe a method for recording synaptic currents and potentials from identified neurons in nearly intact worms. Dissection and exposure of postsynaptic neurons is facilitated by microfabricated agar substrates, and ChannelRhodopsin-2 is used to stimulate presynaptic neurons. We used the method to analyse functional connectivity between a polymodal nociceptor and a command neuron that initiates a stochastic escape behaviour. We find that escape probability mirrors the time course of synaptic current in the command neuron. Moreover, synaptic input increases smoothly as stimulus strength is increased, suggesting that the overall input-output function of the connection is graded. We propose a model in which the energetic cost of escape behaviours in C. elegans is tuned to the intensity of the threat.
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Affiliation(s)
- Theodore H Lindsay
- Institute of Neuroscience, University of Oregon, Eugene, Oregon 97403, USA
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154
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Abstract
hid-1 was originally identified as a Caenorhabditis elegans gene encoding a novel conserved protein that regulates the decision to enter into the enduring dauer larval stage. We isolated a novel allele of hid-1 in a forward genetic screen for mutants mislocalizing RBF-1 rabphilin, a RAB-27 effector. Here we demonstrate that HID-1 functions in the nervous system to regulate neuromuscular signaling and in the intestine to regulate the defecation motor program. We further show that a conserved N-terminal myristoylated motif of both invertebrate and vertebrate HID-1 is essential for its association with intracellular membranes in nematodes and PC12 cells. C. elegans neuronal HID-1 resides on intracellular membranes in neuronal cell somas; however, the kinesin UNC-104 also transports HID-1 to synaptic regions. HID-1 accumulates in the axons of unc-13 and unc-31 mutants, suggesting it is associated with neurosecretory vesicles. Consistent with this, genetic studies place HID-1 in a peptidergic signaling pathway. Finally, a hid-1 null mutation reduces the levels of endogenous neuropeptides and alters the secretion of fluorescent-tagged cargos derived from neuronal and intestinal dense core vesicles (DCVs). Taken together, our findings indicate that HID-1 is a novel component of a DCV-based neurosecretory pathway and that it regulates one or more aspects of the biogenesis, maturation, or trafficking of DCVs.
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155
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Reversal of salt preference is directed by the insulin/PI3K and Gq/PKC signaling in Caenorhabditis elegans. Genetics 2010; 186:1309-19. [PMID: 20837997 DOI: 10.1534/genetics.110.119768] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Animals search for foods and decide their behaviors according to previous experience. Caenorhabditis elegans detects chemicals with a limited number of sensory neurons, allowing us to dissect roles of each neuron for innate and learned behaviors. C. elegans is attracted to salt after exposure to the salt (NaCl) with food. In contrast, it learns to avoid the salt after exposure to the salt without food. In salt-attraction behavior, it is known that the ASE taste sensory neurons (ASEL and ASER) play a major role. However, little is known about mechanisms for learned salt avoidance. Here, through dissecting contributions of ASE neurons for salt chemotaxis, we show that both ASEL and ASER generate salt chemotaxis plasticity. In ASER, we have previously shown that the insulin/PI 3-kinase signaling acts for starvation-induced salt chemotaxis plasticity. This study shows that the PI 3-kinase signaling promotes aversive drive of ASER but not of ASEL. Furthermore, the Gq signaling pathway composed of Gqα EGL-30, diacylglycerol, and nPKC (novel protein kinase C) TTX-4 promotes attractive drive of ASER but not of ASEL. A putative salt receptor GCY-22 guanylyl cyclase is required in ASER for both salt attraction and avoidance. Our results suggest that ASEL and ASER use distinct molecular mechanisms to regulate salt chemotaxis plasticity.
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156
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Roh DH, Yoon SY, Seo HS, Kang SY, Moon JY, Song S, Beitz AJ, Lee JH. Sigma-1 receptor-induced increase in murine spinal NR1 phosphorylation is mediated by the PKCalpha and epsilon, but not the PKCzeta, isoforms. Neurosci Lett 2010; 477:95-9. [PMID: 20417251 DOI: 10.1016/j.neulet.2010.04.041] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 04/16/2010] [Indexed: 02/02/2023]
Abstract
Our previous studies have demonstrated that intrathecal (i.t.) administration of a sigma-1 receptor agonist facilitated peripheral nociception via calcium-dependent second messenger cascades including protein kinase C (PKC). We also showed that activation of spinal sigma-1 receptors increased the phosphorylation of the NMDA receptor NR1 subunit (pNR1) in the spinal cord dorsal horn, which resulted in the potentiation of NMDA receptor function. The present study was designed to examine the effect of different PKC isoform inhibitors on sigma-1 receptor-mediated pain facilitation and increased spinal pNR1 expression in mice. The intrathecal injection of the sigma-1 receptor agonist, PRE-084 (PRE, 3nmol/5mul) increased the frequency of paw withdrawal responses to mechanical stimuli (0.6g) and the number of spinal pNR1-immunoreactive (ir) cells. Intrathecal pretreatment with inhibitors (Go6976, PKCepsilonV1-2 or PKC zetapseudosubstrate) of the PKCalpha, epsilon or zeta isoforms significantly reduced the PRE-induced pain facilitatory effect. On the other hand, the PRE-induced increase in the number of spinal pNR1-ir neurons was only blocked by inhibitors of the PKCalpha and PKCepsilon isoforms, but not the PKCzeta isoform. These findings demonstrate that the sigma-1 receptor-induced increase in spinal pNR1 expression is mediated by the PKCalpha and PKC epsilon isoforms, which in turn contribute to the pain facilitation phenomenon. Conversely, the sigma-1 receptor activation of the PKCzeta isoform appears to be involved in a pain signaling pathway that is independent of spinal pNR1 modulation.
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Affiliation(s)
- Dae-Hyun Roh
- Biotherapy Human Resources Center, College of Veterinary Medicine, Chonnam National University, Gwangju, Republic of Korea
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157
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Neuropeptide feedback modifies odor-evoked dynamics in Caenorhabditis elegans olfactory neurons. Nat Neurosci 2010; 13:615-21. [PMID: 20364145 PMCID: PMC2937567 DOI: 10.1038/nn.2526] [Citation(s) in RCA: 164] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 02/23/2010] [Indexed: 11/21/2022]
Abstract
Many neurons release classical transmitters together with neuropeptide cotransmitters whose functions are incompletely understood. Here we define the relationship between two transmitters in the olfactory system of Caenorhabditis elegans, showing that a neuropeptide-to-neuropeptide feedback loop alters sensory dynamics in primary olfactory neurons. The AWC olfactory neuron is glutamatergic and also expresses the peptide NLP-1. nlp-1 mutants have increased AWC-dependent behaviors, suggesting that NLP-1 limits the normal response. The receptor for NLP-1 is the G protein-coupled receptor NPR-11, which acts in postsynaptic AIA interneurons. Feedback from AIA interneurons modulates odor-evoked calcium dynamics in AWC olfactory neurons and requires INS-1, a neuropeptide released from AIA. The neuropeptide feedback loop dampens behavioral responses to odors on short and long timescales. Our results point to neuronal dynamics as a site of behavioral regulation and reveal the ability of neuropeptide feedback to remodel sensory networks on multiple timescales.
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158
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Alcedo J, Maier W, Ch’ng Q. Sensory Influence on Homeostasis and Lifespan: Molecules and Circuits. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010. [DOI: 10.1007/978-1-4419-7002-2_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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159
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Chen J, Zhang Y, Shen P. Protein kinase C deficiency-induced alcohol insensitivity and underlying cellular targets in Drosophila. Neuroscience 2009; 166:34-9. [PMID: 20006676 DOI: 10.1016/j.neuroscience.2009.12.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 12/03/2009] [Accepted: 12/04/2009] [Indexed: 10/20/2022]
Abstract
Multiple subtypes of protein kinase C (PKC) isozymes are implicated in various neurological disorders including alcohol insensitivity, a trait strongly associated with alcoholism in humans, but molecular and cellular mechanisms underlying the PKC activities remain poorly understood. Here we show that functional knockdown of conventional, novel or atypical PKC in the fly nervous system each resulted in alcohol insensitivity. Neuroanatomical mapping of conventional Ca(2+)-sensitive PKC53E activity uncovers a previously uncharacterized role of Drosophila serotonin neurons in alcohol sensitivity. The deficiency of PKC53E but not novel Ca(2+)-independent PKC98E appears to reduce synaptic serotonin levels, since acute inhibition of serotonin reuptake by citalopram and Prozac reversed alcohol insensitivity in flies expressing PKC53E double-stranded RNA in serotonin neurons. Together, findings from this and our previous studies indicate that PKC53E and PKC98E differentially regulate fly alcohol sensitivity through independent modulation of conserved serotonin and neuropeptide Y-like systems.
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Affiliation(s)
- J Chen
- Department of Cellular Biology and Biomedical and Health Sciences Institute, University of Georgia, 500 DW Brooks Drive, Athens, GA 30602, USA
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160
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O'Halloran DM, Altshuler-Keylin S, Lee JI, L'Etoile ND. Regulators of AWC-mediated olfactory plasticity in Caenorhabditis elegans. PLoS Genet 2009; 5:e1000761. [PMID: 20011101 PMCID: PMC2780698 DOI: 10.1371/journal.pgen.1000761] [Citation(s) in RCA: 43] [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: 06/24/2009] [Accepted: 11/09/2009] [Indexed: 01/29/2023] Open
Abstract
While most sensory neurons will adapt to prolonged stimulation by down-regulating their responsiveness to the signal, it is not clear which events initiate long-lasting sensory adaptation. Likewise, we are just beginning to understand how the physiology of the adapted cell is altered. Caenorhabditis elegans is inherently attracted to specific odors that are sensed by the paired AWC olfactory sensory neurons. The attraction diminishes if the animal experiences these odors for a prolonged period of time in the absence of food. The AWC neuron responds acutely to odor-exposure by closing calcium channels. While odortaxis requires a Gα subunit protein, cGMP-gated channels, and guanylyl cyclases, adaptation to prolonged odor exposure requires nuclear entry of the cGMP-dependent protein kinase, EGL-4. We asked which candidate members of the olfactory signal transduction pathway promote nuclear entry of EGL-4 and which molecules might induce long-term adaptation downstream of EGL-4 nuclear entry. We found that initiation of long-term adaptation, as assessed by nuclear entry of EGL-4, is dependent on G-protein mediated signaling but is independent of fluxes in calcium levels. We show that long-term adaptation requires polyunsaturated fatty acids (PUFAs) that may act on the transient receptor potential (TRP) channel type V OSM-9 downstream of EGL-4 nuclear entry. We also present evidence that high diacylglycerol (DAG) levels block long-term adaptation without affecting EGL-4 nuclear entry. Our analysis provides a model for the process of long-term adaptation that occurs within the AWC neuron of C. elegans: G-protein signaling initiates long-lasting olfactory adaptation by promoting the nuclear entry of EGL-4, and once EGL-4 has entered the nucleus, processes such as PUFA activation of the TRP channel OSM-9 may dampen the output of the AWC neuron. Caenorhabditis elegans is capable of sensing a variety of attractive volatile compounds. These odors are the worm's “best guesses” as to how to track down food. Employing calculated approximations underlies a foraging strategy that is open to failure. When C. elegans track an odor which proves unrewarding, they must modify their behavior based on this experience. They also need to prevent over-stimulating their neurons. To accomplish this, C. elegans olfactory sensory neurons adapt to odors after a sustained exposure to odor in the absence of food. Within the pair of primary odor-sensory neurons, termed the AWCs, adaptation requires the cGMP-dependent protein kinase G (PKG), EGL-4. Exposing animals to AWC–sensed odors for approximately 60 minutes results in a long-lasting (∼3 hour) adaptation that requires the nuclear translocation of EGL-4. To understand how sensory transduction and desensitization machinery converge to achieve olfactory adaptation, we asked whether odor-induced EGL-4 nuclear accumulation was affected by gene mutations that abrogate either odor sensation of or adaptation to AWC–sensed odors. We find that G-protein signaling represents the integration point where primary odor sensation and odor adaptation pathways diverge. PUFA signaling, calcium, and decreased diacylglycerol all dampen the response of the AWC neuron to odor downstream of this divergence.
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Affiliation(s)
- Damien M. O'Halloran
- Center for Neuroscience, University of California Davis, Davis, California, United States of America
| | - Svetlana Altshuler-Keylin
- Center for Neuroscience, University of California Davis, Davis, California, United States of America
| | - Jin I. Lee
- Center for Neuroscience, University of California Davis, Davis, California, United States of America
| | - Noelle D. L'Etoile
- Center for Neuroscience, University of California Davis, Davis, California, United States of America
- Department of Psychiatry and Behavioral Sciences University of California Davis, Davis, California, United States of America
- * E-mail:
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161
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Edwards SL, Charlie NK, Richmond JE, Hegermann J, Eimer S, Miller KG. Impaired dense core vesicle maturation in Caenorhabditis elegans mutants lacking Rab2. ACTA ACUST UNITED AC 2009; 186:881-95. [PMID: 19797080 PMCID: PMC2753164 DOI: 10.1083/jcb.200902095] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Uncoordinated movement in Rab2 mutants is caused by impaired retention of cargo on dense core vesicles, not by defective synaptic vesicle release. (Also see the companion article by Sumakovic et al. in this issue.) Despite a key role for dense core vesicles (DCVs) in neuronal function, there are major gaps in our understanding of DCV biogenesis. A genetic screen for Caenorhabditis elegans mutants with behavioral defects consistent with impaired DCV function yielded five mutations in UNC-108 (Rab2). A genetic analysis showed that unc-108 mutations impair a DCV function unrelated to neuropeptide release that, together with neuropeptide release, fully accounts for the role of DCVs in locomotion. An electron microscopy analysis of DCVs in unc-108 mutants, coupled with quantitative imaging of DCV cargo proteins, revealed that Rab2 acts in cell somas during DCV maturation to prevent the loss of soluble and membrane cargo. In Rab2 null mutants, two thirds of these cargoes move to early endosomes via a PI(3)P-dependent trafficking pathway, whereas aggregated neuropeptides are unaffected. These results reveal how neurons solve a challenging trafficking problem using the most highly conserved animal Rab.
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Affiliation(s)
- Stacey L Edwards
- Genetic Models of Disease Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
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162
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Sumakovic M, Hegermann J, Luo L, Husson SJ, Schwarze K, Olendrowitz C, Schoofs L, Richmond J, Eimer S. UNC-108/RAB-2 and its effector RIC-19 are involved in dense core vesicle maturation in Caenorhabditis elegans. ACTA ACUST UNITED AC 2009; 186:897-914. [PMID: 19797081 PMCID: PMC2753160 DOI: 10.1083/jcb.200902096] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Uncoordinated movement in Rab2 mutants is caused by impaired retention of cargo on dense core vesicles, not by defective synaptic vesicle release. (Also see the companion article by Edwards et al. in this issue.) Small guanosine triphosphatases of the Rab family regulate intracellular vesicular trafficking. Rab2 is highly expressed in the nervous system, yet its function in neurons is unknown. In Caenorhabditis elegans, unc-108/rab-2 mutants have been isolated based on their locomotory defects. We show that the locomotion defects of rab-2 mutants are not caused by defects in synaptic vesicle release but by defects in dense core vesicle (DCV) signaling. DCVs in rab-2 mutants are often enlarged and heterogeneous in size; however, their number and distribution are not affected. This implicates Rab2 in the biogenesis of DCVs at the Golgi complex. We demonstrate that Rab2 is required to prevent DCV cargo from inappropriately entering late endosomal compartments during DCV maturation. Finally, we show that RIC-19, the C. elegans orthologue of the human diabetes autoantigen ICA69, is also involved in DCV maturation and is recruited to Golgi membranes by activated RAB-2. Thus, we propose that RAB-2 and its effector RIC-19 are required for neuronal DCV maturation.
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Affiliation(s)
- Marija Sumakovic
- European Neuroscience Institute Goettingen, German Research Foundation Research Center for Molecular Physiology of the Brain, 37077 Goettingen, Germany
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163
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DeLong ND, Beenhakker MP, Nusbaum MP. Presynaptic inhibition selectively weakens peptidergic cotransmission in a small motor system. J Neurophysiol 2009; 102:3492-504. [PMID: 19828722 DOI: 10.1152/jn.00833.2009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The presence and influence of neurons containing multiple neurotransmitters is well established, including the ability of coreleased transmitters to influence the same or different postsynaptic targets. Little is known, however, regarding whether presynaptic regulation of multitransmitter neurons influences all transmission from these neurons. Using the identified neurons and motor networks in the crab stomatogastric ganglion, we document the ability of presynaptic inhibition to selectively inhibit peptidergic cotransmission. Specifically, we determine that the gastropyloric receptor (GPR) proprioceptor neuron uses presynaptic inhibition to selectively regulate peptidergic cotransmission from the axon terminals of MCN1, a projection neuron that drives the biphasic (retraction, protraction) gastric mill (chewing) rhythm. MCN1 drives this rhythm via fast GABAergic excitation of the retraction neuron Int1 and slow peptidergic excitation of the lateral gastric (LG) protraction neuron. We first demonstrate that GPR inhibition of the MCN1 axon terminals is serotonergic and then establish that this serotonergic inhibition weakens MCN1 peptidergic excitation of LG without altering MCN1 GABAergic excitation of Int1. At the circuit level, we show that this selective regulation of MCN1 peptidergic cotransmission is necessary for the normal GPR regulation of the gastric mill rhythm. This is the first demonstration, at the level of individual identified neurons, that a presynaptic input can selectively regulate a subset of coreleased transmitters. This selective regulation changes the balance of cotransmitter actions by the target multitransmitter neuron, thereby enabling this neuron to have state-dependent actions on its target network. This finding reveals additional flexibility afforded by the ability of neurons to corelease multiple neurotransmitters.
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Affiliation(s)
- Nicholas D DeLong
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6074, USA
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164
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Macosko EZ, Pokala N, Feinberg EH, Chalasani SH, Butcher RA, Clardy J, Bargmann CI. A hub-and-spoke circuit drives pheromone attraction and social behaviour in C. elegans. Nature 2009; 458:1171-5. [PMID: 19349961 PMCID: PMC2760495 DOI: 10.1038/nature07886] [Citation(s) in RCA: 344] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2008] [Accepted: 02/11/2009] [Indexed: 11/29/2022]
Abstract
Innate social behaviors emerge from neuronal circuits that interpret sensory information based on an individual's own genotype, sex, and experience. The regulated aggregation behavior of C. elegans, a simple animal with only 302 neurons, is an attractive system to analyze these circuits. Wild social strains of the nematode Caenorhabditis elegans aggregate in the presence of specific sensory cues, but solitary strains do not1,2,3,4. Here we identify the RMG inter/motor neuron as the hub of a regulated circuit that controls aggregation and related behaviors. RMG is the central site of action of the neuropeptide receptor gene npr-1, which distinguishes solitary strains (high npr-1 activity) from wild social strains (low npr-1 activity); high RMG activity is essential for all aspects of social behavior. Anatomical gap junctions connect RMG to multiple classes of sensory neurons known to promote aggregation, and to ASK sensory neurons, which are implicated in male attraction to hermaphrodite pheromones5. We find that ASK neurons respond directly to pheromones, and that high RMG activity enhances ASK responses in social strains, causing hermaphrodite attraction to pheromones at concentrations that repel solitary hermaphrodites. The coordination of social behaviors by RMG suggests an anatomical hub-and-spoke model for sensory integration in aggregation, and points to functions for related circuit motifs in the C. elegans wiring diagram.
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Affiliation(s)
- Evan Z Macosko
- Howard Hughes Medical Institute, Laboratory of Neural Circuits and Behavior, The Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
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165
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Loss of the transcriptional repressor PAG-3/Gfi-1 results in enhanced neurosecretion that is dependent on the dense-core vesicle membrane protein IDA-1/IA-2. PLoS Genet 2009; 5:e1000447. [PMID: 19343207 PMCID: PMC2657203 DOI: 10.1371/journal.pgen.1000447] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 03/06/2009] [Indexed: 01/09/2023] Open
Abstract
It is generally accepted that neuroendocrine cells regulate dense core vesicle (DCV) biogenesis and cargo packaging in response to secretory demands, although the molecular mechanisms of this process are poorly understood. One factor that has previously been implicated in DCV regulation is IA-2, a catalytically inactive protein phosphatase present in DCV membranes. Our ability to directly visualize a functional, GFP-tagged version of an IA-2 homolog in live Caenorhabditis elegans animals has allowed us to capitalize on the genetics of the system to screen for mutations that disrupt DCV regulation. We found that loss of activity in the transcription factor PAG-3/Gfi-1, which functions as a repressor in many systems, results in a dramatic up-regulation of IDA-1/IA-2 and other DCV proteins. The up-regulation of DCV components was accompanied by an increase in presynaptic DCV numbers and resulted in phenotypes consistent with increased neuroendocrine secretion. Double mutant combinations revealed that these PAG-3 mutant phenotypes were dependent on wild type IDA-1 function. Our results support a model in which IDA-1/IA-2 is a critical element in DCV regulation and reveal a novel genetic link to PAG-3-mediated transcriptional regulation. To our knowledge, this is the first mutation identified that results in increased neurosecretion, a phenotype that has clinical implications for DCV-mediated secretory disorders. Within secretory cells, hormones are packaged into vesicles (called DCVs) that are released upon stimulation. The number of DCVs is regulated to meet the secretory demands of the cell by a mechanism that is poorly understood, although a protein in the membrane of DCVs, called IA-2, is thought to play a role. A genetic screen in the nematode C. elegans is used, here, to find mutations that mis-regulate the corresponding worm protein called IDA-1. Capitalizing on the simple neuroanatomy of the nematode and its transparency, we visualize IDA-1 protein levels directly in the animal using a fluorescent tag. We find that mutations in the transcription factor PAG-3/Gfi-1 result in elevated levels of IDA-1 protein, increased numbers of presynaptic DCVs, and behaviors consistent with increased neurosecretion. Our results demonstrate that IDA-1/IA-2 protein levels correlate with the biogenesis, utilization, or stability of DCVs. We propose that PAG-3 normally down regulates the production of IDA-1, thus serving as part of the mechanism underlying DCV regulation. This is the first reported mutation that increases DCV numbers and secretion, offering insight into DCV homeostasis and a potential therapeutic target for diseases that would benefit from a boost in neuroendocrine secretion.
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166
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Abstract
Neuroendocrine pancreatic islet beta-cells secrete the hormone insulin in response to glucose stimulation and adapt efficiently to increased demand by peripheral tissues to maintain glucose homeostasis. Insulin is packed within dense-core granules, which traffic and dock onto the plasma membrane whereby a Ca(2+) stimulus evokes exocytosis by soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE), complex-mediated, membrane fusion. Recent studies have unveiled postdocking steps mediated by "priming" factors that influence SNARE complex assembly to confer fusion readiness to the docked granules. This review will summarize recent insights into the priming role for Munc13 in the exocytosis of insulin granules. We present evidence for the interaction of Munc13-1 with exocytotic substrates involved in cAMP-mediated potentiation of insulin release, the latter we show to mediate enhanced granule-to-granule fusion events underlying compound exocytosis. We thus also further review the current understanding of granule-to-granule fusion. As agents acting on cAMP signaling are clinically used to augment insulin release in diabetes, this better understanding of priming steps may reveal additional novel therapeutic strategies to increase the capacity for insulin release to improve the treatment of diabetes.
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Affiliation(s)
- Edwin P Kwan
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada.
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167
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Stevens DR, Rettig J. The Ca(2+)-dependent activator protein for secretion CAPS: do I dock or do I prime? Mol Neurobiol 2009; 39:62-72. [PMID: 19160073 DOI: 10.1007/s12035-009-8052-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Accepted: 01/08/2009] [Indexed: 10/21/2022]
Abstract
The "Ca(2+)-dependent activator protein for secretion" (CAPS) is a protein which reconstitutes regulated secretion in permeabilized neuroendocrine cells. It is generally accepted that CAPS plays an important role in the release of the contents of dense core vesicles in the nervous system as well as in a variety of other secretory tissues. At which step in the exocytotic process CAPS functions as well as its role in the fusion of synaptic vesicles is still under dispute. A recent growth spurt in the CAPS field has been fueled by genetic approaches in Caenorhabditis elegans and Drosophila as well as the application of knockout and knockdown approaches in mouse cells and in cell lines, respectively. We have attempted to review the body of work that established CAPS as an important regulator of secretion and to describe new information that has furthered our understanding of how CAPS may function. We discuss the conclusions, point out areas where controversy remains, and suggest directions for future experiments.
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Affiliation(s)
- David R Stevens
- Physiologisches Institut, Universität des Saarlandes, Gebäude 59, Kirrberger Str. 8, 66421, Homburg/Saar, Germany
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168
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Dittman J. Chapter 2 Worm Watching: Imaging Nervous System Structure and Function in Caenorhabditis elegans. ADVANCES IN GENETICS 2009; 65:39-78. [DOI: 10.1016/s0065-2660(09)65002-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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169
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Perez-Mansilla B, Nurrish S. A network of G-protein signaling pathways control neuronal activity in C. elegans. ADVANCES IN GENETICS 2009; 65:145-192. [PMID: 19615533 DOI: 10.1016/s0065-2660(09)65004-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The Caenorhabditis elegans neuromuscular junction (NMJ) is one of the best studied synapses in any organism. A variety of genetic screens have identified genes required both for the essential steps of neurotransmitter release from motorneurons as well as the signaling pathways that regulate rates of neurotransmitter release. A number of these regulatory genes encode proteins that converge to regulate neurotransmitter release. In other cases genes are known to regulate signaling at the NMJ but how they act remains unknown. Many of the proteins that regulate activity at the NMJ participate in a network of heterotrimeric G-protein signaling pathways controlling the release of synaptic vesicles and/or dense-core vesicles (DCVs). At least four heterotrimeric G-proteins (Galphaq, Galpha12, Galphao, and Galphas) act within the motorneurons to control the activity of the NMJ. The Galphaq, Galpha12, and Galphao pathways converge to control production and destruction of the lipid-bound second messenger diacylglycerol (DAG) at sites of neurotransmitter release. DAG acts via at least two effectors, MUNC13 and PKC, to control the release of both neurotransmitters and neuropeptides from motorneurons. The Galphas pathway converges with the other three heterotrimeric G-protein pathways downstream of DAG to regulate neuropeptide release. Released neurotransmitters and neuropeptides then act to control contraction of the body-wall muscles to control locomotion. The lipids and proteins involved in these networks are conserved between C. elegans and mammals. Thus, the C. elegans NMJ acts as a model synapse to understand how neuronal activity in the human brain is regulated.
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Affiliation(s)
- Borja Perez-Mansilla
- MRC Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Department of Neurobiology, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Stephen Nurrish
- MRC Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Department of Neurobiology, Physiology and Pharmacology, University College London, London, United Kingdom
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170
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Roh DH, Kim HW, Yoon SY, Seo HS, Kwon YB, Kim KW, Han HJ, Beitz AJ, Lee JH. Intrathecal administration of sigma-1 receptor agonists facilitates nociception: involvement of a protein kinase C-dependent pathway. J Neurosci Res 2008; 86:3644-54. [PMID: 18655205 DOI: 10.1002/jnr.21802] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sigma sites, originally proposed as opioid receptor subtypes, are currently thought to represent unique receptors with a specific pattern of drug selectivity, a well-established anatomical distribution and broad range of functional roles including potential involvement in nociceptive mechanisms. We have recently demonstrated that intrathecal (i.t.) treatment with a sigma-1 receptor antagonist reduced formalin-induced pain behavior. In the present study, we investigated the potential role of spinal sigma-1 receptor agonists in peripherally initiated nociception and attempted to elucidate intracellular signaling mechanisms associated with spinal cord sigma-1 receptor activation in mice. The i.t. injection of the sigma-1 receptor agonists PRE-084 (PRE) or carbetapentane (CAR) significantly decreased tail-flick latency (TFL) and increased the frequency of paw withdrawal responses to mechanical stimulation (von Frey filament, 0.6 g) as well as the amount of Fos expression in the spinal cord dorsal horn induced by noxious paw-pinch stimulation. These PRE- or CAR-induced facilitatory effects on nociception were significantly blocked by i.t. pretreatment with the sigma-1 receptor antagonist, BD-1047, the phospholipase C (PLC) inhibitor, U-73,122, the Ca(2+)-ATPase inhibitor, thapsigargin, and the protein kinase C (PKC) inhibitor, chelerythrine. Western blot analysis further revealed that i.t. PRE or CAR injection significantly increased pan-PKC as well as the PKCalpha, epsilon, and zeta isoforms in the dorsal horn. Collectively, these findings demonstrate that calcium-dependent second messenger cascades including PKC are involved in the facilitation of nociception associated with spinal sigma-1 receptor activation.
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Affiliation(s)
- Dae-Hyun Roh
- Department of Veterinary Physiology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University, Seoul, South Korea
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171
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Ch'ng Q, Sieburth D, Kaplan JM. Profiling synaptic proteins identifies regulators of insulin secretion and lifespan. PLoS Genet 2008; 4:e1000283. [PMID: 19043554 PMCID: PMC2582949 DOI: 10.1371/journal.pgen.1000283] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Accepted: 10/28/2008] [Indexed: 12/25/2022] Open
Abstract
Cells are organized into distinct compartments to perform specific tasks with spatial precision. In neurons, presynaptic specializations are biochemically complex subcellular structures dedicated to neurotransmitter secretion. Activity-dependent changes in the abundance of presynaptic proteins are thought to endow synapses with different functional states; however, relatively little is known about the rules that govern changes in the composition of presynaptic terminals. We describe a genetic strategy to systematically analyze protein localization at Caenorhabditis elegans presynaptic specializations. Nine presynaptic proteins were GFP-tagged, allowing visualization of multiple presynaptic structures. Changes in the distribution and abundance of these proteins were quantified in 25 mutants that alter different aspects of neurotransmission. Global analysis of these data identified novel relationships between particular presynaptic components and provides a new method to compare gene functions by identifying shared protein localization phenotypes. Using this strategy, we identified several genes that regulate secretion of insulin-like growth factors (IGFs) and influence lifespan in a manner dependent on insulin/IGF signaling. Cells are divided into multiple subcellular compartments that perform diverse functions. In neurons, synapses mediate transmission of information between cells and they comprise hundreds of proteins dedicated for this purpose. Changes in the protein composition of synapses are thought to produce changes in synaptic transmission, such as those that occur during development, learning, and memory. Here, we describe a systematic genetic strategy for analyzing the protein composition of synapses. Using this strategy, we identified sets of genes that alter synapses in similar ways, and identified novel regulatory relationships between particular synaptic proteins. One set of genes regulated secretion of insulin-like hormones from neurons and had corresponding effects on lifespan, which is controlled by insulin signaling. These results illustrate how changes in synaptic composition can be utilized as a probe to explain changes in physiology. Our approach can be expanded to include a larger set of synaptic proteins or to analyze other subcellular compartments.
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Affiliation(s)
- QueeLim Ch'ng
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- * E-mail: (QC); (JMK)
| | - Derek Sieburth
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Joshua M. Kaplan
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- * E-mail: (QC); (JMK)
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172
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Abstract
Animal behaviors are subjected to innate preferences, which are usually encoded by dedicated sensory neurons. In this issue of Neuron, Tsunozaki and colleagues show that one olfactory neuron in Caenorhabditis elegans produces two opposing preferences to an odor by regulating cGMP and PKC signaling.
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173
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Graham ME, Edwards MR, Holden-Dye L, Morgan A, Burgoyne RD, Barclay JW. UNC-18 modulates ethanol sensitivity in Caenorhabditis elegans. Mol Biol Cell 2008; 20:43-55. [PMID: 18923141 DOI: 10.1091/mbc.e08-07-0689] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Acute ethanol exposure affects the nervous system as a stimulant at low concentrations and as a depressant at higher concentrations, eventually resulting in motor dysfunction and uncoordination. A recent genetic study of two mouse strains with varying ethanol preference indicated a correlation with a polymorphism (D216N) in the synaptic protein Munc18-1. Munc18-1 functions in exocytosis via a number of discrete interactions with the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein syntaxin-1. We report that the mutation affects binding to syntaxin but not through either a closed conformation mode of interaction or through binding to the syntaxin N terminus. The D216N mutant instead has a specific impairment in binding the assembled SNARE complex. Furthermore, the mutation broadens the duration of single exocytotic events. Expression of the orthologous mutation (D214N) in the Caenorhabditis elegans UNC-18 null background generated transgenic rescues with phenotypically similar locomotion to worms rescued with the wild-type protein. Strikingly, D214N worms were strongly resistant to both stimulatory and sedative effects of acute ethanol. Analysis of an alternative Munc18-1 mutation (I133V) supported the link between reduced SNARE complex binding and ethanol resistance. We conclude that ethanol acts, at least partially, at the level of vesicle fusion and that its acute effects are ameliorated by point mutations in UNC-18.
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Affiliation(s)
- Margaret E Graham
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, United Kingdom
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174
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Abstract
The role of neuropeptides in modulating behavior is slowly being elucidated. With the sequencing of the C. elegans genome, the extent of the neuropeptide genes in C. elegans can be determined. To date, 113 neuropeptide genes encoding over 250 distinct neuropeptides have been identified. Of these, 40 genes encode insulin-like peptides, 31 genes encode FMRFamide-related peptides, and 42 genes encode non-insulin, non-FMRFamide-related neuropeptides. As in other systems, C. elegans neuropeptides are derived from precursor molecules that must be post-translationally processed to yield the active peptides. These precursor molecules contain a single peptide, multiple copies of a single peptide, multiple distinct peptides, or any combination thereof. The neuropeptide genes are expressed extensively throughout the nervous system, including in sensory, motor, and interneurons. In addition, some of the genes are also expressed in non-neuronal tissues, such as the somatic gonad, intestine, and vulval hypodermis. To address the effects of neuropeptides on C. elegans behavior, animals in which the different neuropeptide genes are inactivated or overexpressed are being isolated. In a complementary approach the receptors to which the neuropeptides bind are also being identified and examined. Among the knockout animals analyzed thus far, defects in locomotion, dauer formation, egg laying, ethanol response, and social behavior have been reported. These data suggest that neuropeptides have a modulatory role in many, if not all, behaviors in C. elegans.
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Affiliation(s)
- Chris Li
- Department of Biology, City College of New York, New York, NY 10031, USA.
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175
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Tsunozaki M, Chalasani SH, Bargmann CI. A behavioral switch: cGMP and PKC signaling in olfactory neurons reverses odor preference in C. elegans. Neuron 2008; 59:959-71. [PMID: 18817734 PMCID: PMC2586605 DOI: 10.1016/j.neuron.2008.07.038] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 04/19/2008] [Accepted: 07/25/2008] [Indexed: 12/11/2022]
Abstract
Innate chemosensory preferences are often encoded by sensory neurons that are specialized for attractive or avoidance behaviors. Here, we show that one olfactory neuron in Caenorhabditis elegans, AWC(ON), has the potential to direct both attraction and repulsion. Attraction, the typical AWC(ON) behavior, requires a receptor-like guanylate cyclase GCY-28 that acts in adults and localizes to AWC(ON) axons. gcy-28 mutants avoid AWC(ON)-sensed odors; they have normal odor-evoked calcium responses in AWC(ON) but reversed turning biases in odor gradients. In addition to gcy-28, a diacylglycerol/protein kinase C pathway that regulates neurotransmission switches AWC(ON) odor preferences. A behavioral switch in AWC(ON) may be part of normal olfactory plasticity, as odor conditioning can induce odor avoidance in wild-type animals. Genetic interactions, acute rescue, and calcium imaging suggest that the behavioral reversal results from presynaptic changes in AWC(ON). These results suggest that alternative modes of neurotransmission can couple one sensory neuron to opposite behavioral outputs.
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Affiliation(s)
- Makoto Tsunozaki
- Howard Hughes Medical Institute, Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, NY 10065, USA
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176
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Chen J, Zhang Y, Shen P. A protein kinase C activity localized to neuropeptide Y–like neurons mediates ethanol intoxication in Drosophila melanogaster. Neuroscience 2008; 156:42-7. [DOI: 10.1016/j.neuroscience.2008.07.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Revised: 07/03/2008] [Accepted: 07/08/2008] [Indexed: 10/21/2022]
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177
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Vashlishan AB, Madison JM, Dybbs M, Bai J, Sieburth D, Ch'ng Q, Tavazoie M, Kaplan JM. An RNAi Screen Identifies Genes that Regulate GABA Synapses. Neuron 2008; 58:346-61. [DOI: 10.1016/j.neuron.2008.02.019] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Revised: 02/12/2008] [Accepted: 02/19/2008] [Indexed: 01/29/2023]
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178
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Chun DK, McEwen JM, Burbea M, Kaplan JM. UNC-108/Rab2 regulates postendocytic trafficking in Caenorhabditis elegans. Mol Biol Cell 2008; 19:2682-95. [PMID: 18434599 DOI: 10.1091/mbc.e07-11-1120] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
After endocytosis, membrane proteins are often sorted between two alternative pathways: a recycling pathway and a degradation pathway. Relatively little is known about how trafficking through these alternative pathways is differentially regulated. Here, we identify UNC-108/Rab2 as a regulator of postendocytic trafficking in both neurons and coelomocytes. Mutations in the Caenorhabditis elegans Rab2 gene unc-108, caused the green fluorescent protein (GFP)-tagged glutamate receptor GLR-1 (GLR-1::GFP) to accumulate in the ventral cord and in neuronal cell bodies. In neuronal cell bodies of unc-108/Rab2 mutants, GLR-1::GFP was found in tubulovesicular structures that colocalized with markers for early and recycling endosomes, including Syntaxin-13 and Rab8. GFP-tagged Syntaxin-13 also accumulated in the ventral cord of unc-108/Rab2 mutants. UNC-108/Rab2 was not required for ubiquitin-mediated sorting of GLR-1::GFP into the multivesicular body (MVB) degradation pathway. Mutations disrupting the MVB pathway and unc-108/Rab2 mutations had additive effects on GLR-1::GFP levels in the ventral cord. In coelomocytes, postendocytic trafficking of the marker Texas Red-bovine serum albumin was delayed. These results demonstrate that UNC-108/Rab2 regulates postendocytic trafficking, most likely at the level of early or recycling endosomes, and that UNC-108/Rab2 and the MVB pathway define alternative postendocytic trafficking mechanisms that operate in parallel. These results define a new function for Rab2 in protein trafficking.
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Affiliation(s)
- Denise K Chun
- Department of Molecular Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston MA 02114, USA
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179
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Xu T, Xu P. Searching for Molecular Players Differentially Involved in Neurotransmitter and Neuropeptide Release. Neurochem Res 2008; 33:1915-9. [DOI: 10.1007/s11064-008-9648-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2007] [Accepted: 02/29/2008] [Indexed: 11/24/2022]
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180
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Tokuoka SM, Saiardi A, Nurrish SJ. The mood stabilizer valproate inhibits both inositol- and diacylglycerol-signaling pathways in Caenorhabditis elegans. Mol Biol Cell 2008; 19:2241-50. [PMID: 18287529 DOI: 10.1091/mbc.e07-09-0982] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The antiepileptic valproate (VPA) is widely used in the treatment of bipolar disorder, although the mechanism of its action in the disorder is unclear. We show here that VPA inhibits both inositol phosphate and diacylglycerol (DAG) signaling in Caenorhabditis elegans. VPA disrupts two behaviors regulated by the inositol-1,4,5-trisphosphate (IP(3)): defecation and ovulation. VPA also inhibits two activities regulated by DAG signaling: acetylcholine release and egg laying. The effects of VPA on DAG signaling are relieved by phorbol ester, a DAG analogue, suggesting that VPA acts to inhibit DAG production. VPA reduces levels of DAG and inositol-1-phosphate, but phosphatidylinositol-4,5-bisphosphate (PIP(2)) is slightly increased, suggesting that phospholipase C-mediated hydrolysis of PIP(2) to form DAG and IP(3) is defective in the presence of VPA.
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Affiliation(s)
- Suzumi M Tokuoka
- MRC Cell Biology Unit, MRC Laboratory for Molecular Cell Biology, Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, United Kingdom
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181
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Hammarlund M, Watanabe S, Schuske K, Jorgensen EM. CAPS and syntaxin dock dense core vesicles to the plasma membrane in neurons. ACTA ACUST UNITED AC 2008; 180:483-91. [PMID: 18250196 PMCID: PMC2234227 DOI: 10.1083/jcb.200708018] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Docking to the plasma membrane prepares vesicles for rapid release. Here, we describe a mechanism for dense core vesicle docking in neurons. In Caenorhabditis elegans motor neurons, dense core vesicles dock at the plasma membrane but are excluded from active zones at synapses. We have found that the calcium-activated protein for secretion (CAPS) protein is required for dense core vesicle docking but not synaptic vesicle docking. In contrast, we see that UNC-13, a docking factor for synaptic vesicles, is not essential for dense core vesicle docking. Both the CAPS and UNC-13 docking pathways converge on syntaxin, a component of the SNARE (soluble N-ethyl-maleimide-sensitive fusion protein attachment receptor) complex. Overexpression of open syntaxin can bypass the requirement for CAPS in dense core vesicle docking. Thus, CAPS likely promotes the open state of syntaxin, which then docks dense core vesicles. CAPS function in dense core vesicle docking parallels UNC-13 in synaptic vesicle docking, which suggests that these related proteins act similarly to promote docking of independent vesicle populations.
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Affiliation(s)
- Marc Hammarlund
- Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
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182
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Affiliation(s)
- Rachel McMullan
- Medical Research Council Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Department of Pharmacology, University College, London WC1E 6BT, United Kingdom
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183
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Zhou KM, Dong YM, Ge Q, Zhu D, Zhou W, Lin XG, Liang T, Wu ZX, Xu T. PKA Activation Bypasses the Requirement for UNC-31 in the Docking of Dense Core Vesicles from C. elegans Neurons. Neuron 2007; 56:657-69. [DOI: 10.1016/j.neuron.2007.09.015] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Revised: 03/07/2007] [Accepted: 09/06/2007] [Indexed: 10/22/2022]
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184
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Van Kolen K, Pullan S, Neefs JM, Dautzenberg FM. Nociceptive and behavioural sensitisation by protein kinase Cepsilon signalling in the CNS. J Neurochem 2007; 104:1-13. [PMID: 17971128 DOI: 10.1111/j.1471-4159.2007.04986.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Despite the apparent homology in the protein kinase C (PKC) family, it has become clear that slight structural differences are sufficient to have unique signalling properties for each individual isoform. For PKCepsilon in depth investigation of these aspects revealed unique actions in the CNS and lead to development of specific modulators with clinical perspective. In this review, we describe to which extent PKCepsilon is distinct from other isoforms on the level of tissue expression and protein structure. As this kinase is highly expressed in the brain, we outline three main aspects of PKCepsilon signalling in the CNS. First, its ability to alter the permeability of N-type Ca2+ channels in dorsal root ganglia has been shown to enhance nociception. Secondly, PKCepsilon increases anxiety by diminishing GABA(A)R-induced inhibitory post-synaptic currents in the prefrontal cortex. Another important aspect of the latter inhibition is the reduced sensitivity of GABA(A) receptors to ethanol, a mechanism potentially contributing to abuse. A third signalling cascade improves cognitive functions by facilitating cholinergic signalling in the hippocampus. Collectively, these findings point to a physical and behavioural sensitising role for this kinase.
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Affiliation(s)
- Kristof Van Kolen
- CNS Research, Johnson & Johnson Pharmaceutical Research and Development, Beerse, Belgium.
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185
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Gracheva EO, Burdina AO, Touroutine D, Berthelot-Grosjean M, Parekh H, Richmond JE. Tomosyn negatively regulates CAPS-dependent peptide release at Caenorhabditis elegans synapses. J Neurosci 2007; 27:10176-84. [PMID: 17881523 PMCID: PMC3874420 DOI: 10.1523/jneurosci.2339-07.2007] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The syntaxin-interacting protein tomosyn is thought to be a key regulator of exocytosis, although its precise mechanism of action has yet to be elucidated. Here we examined the role of tomosyn in peptide secretion in Caenorhabditis elegans tomosyn (tom-1) mutants. Ultrastructural analysis of tom-1 mutants revealed a 50% reduction in presynaptic dense-core vesicles (DCVs) corresponding to enhanced neuropeptide release. Conversely, overexpression of TOM-1 led to an accumulation of DCVs. Together, these data provide the first in vivo evidence that TOM-1 negatively regulates DCV exocytosis. In C. elegans, neuropeptide release is promoted by the calcium-dependent activator protein for secretion (CAPS) homolog UNC-31. To test for a genetic interaction between tomosyn and CAPS, we generated tom-1;unc-31 double mutants. Loss of TOM-1 suppressed the behavioral, electrophysiological, and DCV ultrastructural phenotypes of unc-31 mutants, indicating that TOM-1 antagonizes UNC-31-dependent DCV release. Because unc-31 mutants exhibit synaptic transmission defects, we postulated that loss of DCV release in these mutants and the subsequent suppression by tom-1 mutants could simply reflect alterations in synaptic activity, rather than direct regulation of DCV release. To distinguish between these two possibilities, we analyzed C. elegans Rim mutants (unc-10), which have a comparable reduction in synaptic transmission to unc-31 mutants, specifically attributed to defects in synaptic vesicle (SV) exocytosis. Based on this analysis, we conclude that the changes in DCV release in tom-1 and unc-31 mutants reflect direct effects of TOM-1 and UNC-31 on DCV exocytosis, rather than altered SV release.
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Affiliation(s)
- Elena O Gracheva
- Department of Biological Sciences, Science and Engineering Labs, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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186
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Hu JY, Chen Y, Schacher S. Protein kinase C regulates local synthesis and secretion of a neuropeptide required for activity-dependent long-term synaptic plasticity. J Neurosci 2007; 27:8927-39. [PMID: 17699674 PMCID: PMC6672177 DOI: 10.1523/jneurosci.2322-07.2007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Long-term facilitation (LTF) of sensory neuron synapses in Aplysia is produced by either nonassociative or associative stimuli. Nonassociative LTF can be produced by five spaced applications of serotonin (5-HT) and requires a phosphoinosotide 3-kinase (PI3K)-dependent and rapamycin-sensitive increase in the local synthesis of the sensory neuron neuropeptide sensorin and a protein kinase A (PKA)-dependent increase in the secretion of the newly synthesized sensorin. We report here that associative LTF produced by a single pairing of a brief tetanus with one application of 5-HT requires a rapid protein kinase C (PKC)-dependent and rapamycin-sensitive increase in local sensorin synthesis. This rapid increase in sensorin synthesis does not require PI3K activity or the presence of the sensory neuron cell body but does require the presence of the motor neuron. The secretion of newly synthesized sensorin by 2 h after stimulation requires both PKA and PKC activities to produce associative LTF because incubation with exogenous anti-sensorin antibody or the kinase inhibitors after tetanus plus 5-HT blocked LTF. The secreted sensorin leads to phosphorylation and translocation of p42/44 mitogen-activated protein kinase (MAPK) into the nuclei of the sensory neurons. Thus, different stimuli activating different signaling pathways converge by regulating the synthesis and release of a neuropeptide to produce long-term synaptic plasticity.
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Affiliation(s)
- Jiang-Yuan Hu
- Center for Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, New York, New York 10032
| | - Yang Chen
- Center for Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, New York, New York 10032
| | - Samuel Schacher
- Center for Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, New York, New York 10032
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187
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Gracheva EO, Burdina AO, Touroutine D, Berthelot-Grosjean M, Parekh H, Richmond JE. Tomosyn negatively regulates both synaptic transmitter and neuropeptide release at the C. elegans neuromuscular junction. J Physiol 2007; 585:705-9. [PMID: 17627987 PMCID: PMC2375516 DOI: 10.1113/jphysiol.2007.138321] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The SNARE proteins, syntaxin, SNAP-25 and synaptobrevin form a tertiary complex essential for vesicle fusion. Proteins that influence SNARE complex assembly are therefore likely to be important regulators of fusion events. In this study we have focused on tomosyn, a highly conserved, neuronally enriched, syntaxin-binding protein that has been implicated in the regulation of vesicle exocytosis. To directly test the role of tomosyn in neurosecretion we analysed loss-of-function mutants in the single Caenorhabditis elegans tomosyn gene, tom-1. These mutants exhibit enhanced synaptic transmission based on electrophysiological analysis of neuromuscular junction activity. This phenotype is the result of increased synaptic vesicle priming. In addition, we present evidence that tom-1 mutants also exhibit enhanced peptide release from dense core vesicles. These results indicate that tomosyn negatively regulates secretion for both vesicle types, possibly through a common mechanism, interfering with SNARE complex formation, thereby inhibiting vesicle fusion.
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Affiliation(s)
- Elena O Gracheva
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL, USA
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188
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Speese S, Petrie M, Schuske K, Ailion M, Ann K, Iwasaki K, Jorgensen EM, Martin TFJ. UNC-31 (CAPS) is required for dense-core vesicle but not synaptic vesicle exocytosis in Caenorhabditis elegans. J Neurosci 2007; 27:6150-62. [PMID: 17553987 PMCID: PMC6672138 DOI: 10.1523/jneurosci.1466-07.2007] [Citation(s) in RCA: 217] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Previous studies indicated that CAPS (calcium-dependent activator protein for secretion) functions as an essential component for the Ca2+-dependent exocytosis of dense-core vesicles in neuroendocrine cells. However, recent mouse knock-out studies suggested an alternative role in the vesicular uptake or storage of catecholamines. To genetically assess the functional role of CAPS, we characterized the sole Caenorhabditis elegans CAPS ortholog UNC-31 (uncoordinated family member) and determined its role in dense-core vesicle-mediated peptide secretion and in synaptic vesicle recycling. Novel assays for dense-core vesicle exocytosis were developed by expressing a prepro-atrial natriuretic factor-green fluorescent protein fusion protein in C. elegans. unc-31 mutants exhibited reduced peptide release in vivo and lacked evoked peptide release in cultured neurons. In contrast, cultured neurons from unc-31 mutants exhibited normal stimulated synaptic vesicle recycling measured by FM4-64 [N-(3-triethylammoniumpropyl)-4-(6-(4-diethylamino)phenyl)hexatrienyl)pyridinium dibromide] dye uptake. Conversely, UNC-13, which exhibits sequence homology to CAPS/UNC-31, was found to be essential for synaptic vesicle but not dense-core vesicle exocytosis. These findings indicate that CAPS/UNC-31 function is not restricted to catecholaminergic vesicles but is generally required for and specific to dense-core vesicle exocytosis. Our results suggest that CAPS/UNC-31 and UNC-13 serve parallel and dedicated roles in dense-core vesicle and synaptic vesicle exocytosis, respectively, in the C. elegans nervous system.
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Affiliation(s)
- Sean Speese
- Department of Biology, University of Utah, Salt Lake City, Utah 84112
| | - Matt Petrie
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin 53706, and
| | - Kim Schuske
- Department of Biology, University of Utah, Salt Lake City, Utah 84112
| | - Michael Ailion
- Department of Biology, University of Utah, Salt Lake City, Utah 84112
| | - Kyoungsook Ann
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin 53706, and
| | - Kouichi Iwasaki
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, Illinois 60611
| | - Erik M. Jorgensen
- Department of Biology, University of Utah, Salt Lake City, Utah 84112
| | - Thomas F. J. Martin
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin 53706, and
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189
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Abstract
Protein kinase C has long been thought to mediate DAG signaling at the synapse. Recently PKC has been supplanted by members of the Unc13 family as the predominant effectors of DAG signaling. Thanks to a study by Wierda and colleagues in this issue of Neuron, PKC returns to reclaim part of the kingdom: both pathways must be active to activate presynaptic potentiation.
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Affiliation(s)
- Mark Palfreyman
- Department of Biology and Howard Hughes Medical Institute, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112-0840, USA
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190
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Abstract
Protein kinase Cs (PKCs) are implicated in many forms of synaptic plasticity. However, the specific isoform(s) of PKC that underlie(s) these events are often not known. We have used Aplysia as a model system in order to investigate the isoform specificity of PKC actions due to the presence of fewer isoforms and a large number of documented physiological roles for PKC in synaptic plasticity in this system. In particular, we have shown that distinct isoforms mediate distinct types of synaptic plasticity induced by the same neurotransmitter: The novel calcium-independent PKC Apl II is required for actions mediated by serotonin (5-HT) alone, while the classical calcium-dependent PKC Apl I is required for actions mediated when 5-HT is coupled to activity. We will discuss the reasons for PKC isoform specificity, assess the tools used to uncover isoform specificity, and discuss the implications of isoform specificity for understanding the roles of PKC in regulating synaptic plasticity.
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Affiliation(s)
- Wayne S Sossin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
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