1
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Liang X, Taylor M, Napier-Jameson R, Calovich-Benne C, Norris A. A Conserved Role for Stomatin Domain Genes in Olfactory Behavior. eNeuro 2023; 10:ENEURO.0457-22.2023. [PMID: 36858824 PMCID: PMC10035767 DOI: 10.1523/eneuro.0457-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 02/15/2023] [Accepted: 02/23/2023] [Indexed: 03/03/2023] Open
Abstract
The highly-conserved stomatin domain has been identified in genes throughout all classes of life. In animals, different stomatin domain-encoding genes have been implicated in the function of the kidney, red blood cells, and specific neuron types, although the underlying mechanisms remain unresolved. In one well-studied example of stomatin domain gene function, the Caenorhabditis elegans gene mec-2 and its mouse homolog Stoml3 are required for the function of mechanosensory neurons, where they modulate the activity of mechanosensory ion channels on the plasma membrane. Here, we identify an additional shared function for mec-2 and Stoml3 in a very different sensory context, that of olfaction. In worms, we find that a subset of stomatin domain genes are expressed in olfactory neurons, but only mec-2 is strongly required for olfactory behavior. mec-2 acts cell-autonomously and multiple alternatively-spliced isoforms of mec-2 can be substituted for each other. We generate a Stoml3 knock-out (KO) mouse and demonstrate that, like its worm homolog mec-2, it is required for olfactory behavior. In mice, Stoml3 is not required for odor detection, but is required for odor discrimination. Therefore, in addition to their shared roles in mechanosensory behavior, mec-2 and Stoml3 also have a shared role in olfactory behavior.
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Affiliation(s)
- Xiaoyu Liang
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275
| | - Morgan Taylor
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275
| | | | - Canyon Calovich-Benne
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275
| | - Adam Norris
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275
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2
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Hendi A, Niu LG, Snow AW, Ikegami R, Wang ZW, Mizumoto K. Channel-independent function of UNC-9/Innexin in spatial arrangement of GABAergic synapses in C. elegans. eLife 2022; 11:80555. [PMID: 36378164 PMCID: PMC9665852 DOI: 10.7554/elife.80555] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 11/03/2022] [Indexed: 11/16/2022] Open
Abstract
Precise synaptic connection of neurons with their targets is essential for the proper functioning of the nervous system. A plethora of signaling pathways act in concert to mediate the precise spatial arrangement of synaptic connections. Here we show a novel role for a gap junction protein in controlling tiled synaptic arrangement in the GABAergic motor neurons in Caenorhabditis elegans, in which their axons and synapses overlap minimally with their neighboring neurons within the same class. We found that while EGL-20/Wnt controls axonal tiling, their presynaptic tiling is mediated by a gap junction protein UNC-9/Innexin, that is localized at the presynaptic tiling border between neighboring dorsal D-type GABAergic motor neurons. Strikingly, the gap junction channel activity of UNC-9 is dispensable for its function in controlling tiled presynaptic patterning. While gap junctions are crucial for the proper functioning of the nervous system as channels, our finding uncovered the novel channel-independent role of UNC-9 in synapse patterning.
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Affiliation(s)
- Ardalan Hendi
- Department of Zoology, University of British Columbia
- Life Sciences Institute, University of British Columbia
| | - Long-Gang Niu
- Department of Neuroscience, University of Connecticut Health Center
| | - Andrew William Snow
- Graduate Program in Cell and Developmental Biology, University of British Columbia
| | | | - Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut Health Center
| | - Kota Mizumoto
- Department of Zoology, University of British Columbia
- Life Sciences Institute, University of British Columbia
- Graduate Program in Cell and Developmental Biology, University of British Columbia
- Djavad Mowafaghian Centre for Brain Health, University of British Columbia
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3
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Sexually dimorphic architecture and function of a mechanosensory circuit in C. elegans. Nat Commun 2022; 13:6825. [PMID: 36369281 PMCID: PMC9652301 DOI: 10.1038/s41467-022-34661-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 11/01/2022] [Indexed: 11/13/2022] Open
Abstract
How sensory perception is processed by the two sexes of an organism is still only partially understood. Despite some evidence for sexual dimorphism in auditory and olfactory perception, whether touch is sensed in a dimorphic manner has not been addressed. Here we find that the neuronal circuit for tail mechanosensation in C. elegans is wired differently in the two sexes and employs a different combination of sex-shared sensory neurons and interneurons in each sex. Reverse genetic screens uncovered cell- and sex-specific functions of the alpha-tubulin mec-12 and the sodium channel tmc-1 in sensory neurons, and of the glutamate receptors nmr-1 and glr-1 in interneurons, revealing the underlying molecular mechanisms that mediate tail mechanosensation. Moreover, we show that only in males, the sex-shared interneuron AVG is strongly activated by tail mechanical stimulation, and accordingly is crucial for their behavioral response. Importantly, sex reversal experiments demonstrate that the sexual identity of AVG determines both the behavioral output of the mechanosensory response and the molecular pathways controlling it. Our results present extensive sexual dimorphism in a mechanosensory circuit at both the cellular and molecular levels.
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4
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Ferdousy S, Chen B. An assessment of genome-editing efficiency of a newly developed Cas9 in C. elegans. MICROPUBLICATION BIOLOGY 2022; 2022:10.17912/micropub.biology.000601. [PMID: 35903778 PMCID: PMC9315413 DOI: 10.17912/micropub.biology.000601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 07/10/2022] [Accepted: 07/12/2022] [Indexed: 11/22/2022]
Abstract
Minimizing the off-target effects of the programmable genome editing tool CRISPR/Cas9 is critical for its potential therapeutic applications. A recent study reported a new Cas9 variant, SuperFi-Cas9, that dramatically reduces off-target DNA cleavage while retaining on-target DNA cleavage activity in in vitro assays. Here we evaluated the genome editing potential of SuperFi-Cas9 by examining its efficiency in mutagenizing targeted genes in the nematode C. elegans . We found that gene mutagenesis rates induced by SuperFi-Cas9 through either non-homologous end joining or homology-directed repair were much lower than those by the wild type Cas9, indicating that Super-Cas9 had very low in vivo DNA cleavage activity. Our results also suggest that C. elegans may serve as an excellent model system for assessing in vivo genome-editing efficiency of newly-developed Cas9 variants.
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Affiliation(s)
- Sakia Ferdousy
- Southern Illinois University Carbondale, Carbondale, IL, USA
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BCSIR Laboratories Chattogram, Bangladesh Council of Scientific and Industrial Research, Chattogram, Bangladesh
| | - Bojun Chen
- Southern Illinois University Carbondale, Carbondale, IL, USA
,
Correspondence to: Bojun Chen (
)
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5
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Multiview motion tracking based on a cartesian robot to monitor Caenorhabditis elegans in standard Petri dishes. Sci Rep 2022; 12:1767. [PMID: 35110654 PMCID: PMC8810772 DOI: 10.1038/s41598-022-05823-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 01/17/2022] [Indexed: 12/02/2022] Open
Abstract
Data from manual healthspan assays of the nematode Caenorhabditis elegans (C. elegans) can be complex to quantify. The first attempts to quantify motor performance were done manually, using the so-called thrashing or body bends assay. Some laboratories have automated these approaches using methods that help substantially to quantify these characteristic movements in small well plates. Even so, it is sometimes difficult to find differences in motor behaviour between strains, and/or between treated vs untreated worms. For this reason, we present here a new automated method that increases the resolution flexibility, in order to capture more movement details in large standard Petri dishes, in such way that those movements are less restricted. This method is based on a Cartesian robot, which enables high-resolution images capture in standard Petri dishes. Several cameras mounted strategically on the robot and working with different fields of view, capture the required C. elegans visual information. We have performed a locomotion-based healthspan experiment with several mutant strains, and we have been able to detect statistically significant differences between two strains that show very similar movement patterns.
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6
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Sordillo A, Bargmann CI. Behavioral control by depolarized and hyperpolarized states of an integrating neuron. eLife 2021; 10:e67723. [PMID: 34738904 PMCID: PMC8570696 DOI: 10.7554/elife.67723] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Accepted: 10/19/2021] [Indexed: 12/11/2022] Open
Abstract
Coordinated transitions between mutually exclusive motor states are central to behavioral decisions. During locomotion, the nematode Caenorhabditis elegans spontaneously cycles between forward runs, reversals, and turns with complex but predictable dynamics. Here, we provide insight into these dynamics by demonstrating how RIM interneurons, which are active during reversals, act in two modes to stabilize both forward runs and reversals. By systematically quantifying the roles of RIM outputs during spontaneous behavior, we show that RIM lengthens reversals when depolarized through glutamate and tyramine neurotransmitters and lengthens forward runs when hyperpolarized through its gap junctions. RIM is not merely silent upon hyperpolarization: RIM gap junctions actively reinforce a hyperpolarized state of the reversal circuit. Additionally, the combined outputs of chemical synapses and gap junctions from RIM regulate forward-to-reversal transitions. Our results indicate that multiple classes of RIM synapses create behavioral inertia during spontaneous locomotion.
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Affiliation(s)
- Aylesse Sordillo
- Lulu and Anthony Wang Laboratory of Neural Circuits and Behavior, The Rockefeller UniversityNew YorkUnited States
| | - Cornelia I Bargmann
- Lulu and Anthony Wang Laboratory of Neural Circuits and Behavior, The Rockefeller UniversityNew YorkUnited States
- Chan Zuckerberg InitiativeRedwood CityUnited States
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7
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Meng L, Yan D. NLR-1/CASPR Anchors F-Actin to Promote Gap Junction Formation. Dev Cell 2020; 55:574-587.e3. [PMID: 33238150 DOI: 10.1016/j.devcel.2020.10.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 08/05/2020] [Accepted: 10/28/2020] [Indexed: 12/31/2022]
Abstract
Gap junctions are present in most tissues and play essential roles in various biological processes. However, we know surprisingly little about the molecular mechanisms underlying gap junction formation. Here, we uncover the essential role of a conserved EGF- and laminin-G-domain-containing protein nlr-1/CASPR in the regulation of gap junction formation in multiple tissues across different developmental stages in C. elegans. NLR-1 is located in the gap junction perinexus, a region adjacent to but not overlapping with gap junctions, and forms puncta before the clusters of gap junction channels appear on the membrane. We show that NLR-1 can directly bind to actin to recruit F-actin networks at the gap junction formation plaque, and the formation of F-actin patches plays a critical role in the assembly of gap junction channels. Our findings demonstrate that nlr-1/CASPR acts as an early stage signal for gap junction formation through anchoring of F-actin networks.
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Affiliation(s)
- Lingfeng Meng
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Dong Yan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA; Department of Neurobiology, Regeneration Next, and Duke Institute for Brain Sciences, Duke University Medical Center, Durham, NC 27710, USA.
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8
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Guan L, Zhan Z, Yang Y, Miao Y, Huang X, Ding M. Alleviating chronic ER stress by p38-Ire1-Xbp1 pathway and insulin-associated autophagy in C. elegans neurons. PLoS Genet 2020; 16:e1008704. [PMID: 32986702 PMCID: PMC7544145 DOI: 10.1371/journal.pgen.1008704] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 10/08/2020] [Accepted: 08/11/2020] [Indexed: 01/07/2023] Open
Abstract
ER stress occurs in many physiological and pathological conditions. However, how chronic ER stress is alleviated in specific cells in an intact organism is an outstanding question. Here, overexpressing the gap junction protein UNC-9 (Uncoordinated) in C. elegans neurons triggers the Ire1-Xbp1-mediated stress response in an age-dependent and cell-autonomous manner. The p38 MAPK PMK-3 regulates the chronic stress through IRE-1 phosphorylation. Overexpressing gap junction protein also activates autophagy. The insulin pathway functions through autophagy, but not the transcription of genes encoding ER chaperones, to counteract the p38-Ire1-Xbp1-mediated stress response. Together, these results reveal an intricate cellular regulatory network in response to chronic stress in a subset of cells in multicellular organism. The accumulation of unfolded proteins triggers the ER stress response (UPR), which allows cells to fight against fluctuations in protein expression under both physiological and pathological conditions. Severe acute ER stress responses can be induced by drug treatment. However, such intense ER stress rarely occurs ubiquitously in every cell type in vivo. Here, we designed a genetic system in the nematode C. elegans, which allows us to induce ER stress in specific cells, without drug treatment or any other external stimuli, and then to monitor the stress response. The p38 MAPK directly acts on the phosphorylation of IRE-1 to promote the stress response. Meanwhile, the insulin receptor function through autophagy activation to counteract the p38-IRE-1-XBP-1 pathway. Together, these results reveal an intricate cellular regulatory network in response to chronic stress in multicellular organism.
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Affiliation(s)
- Liying Guan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- * E-mail: (LG); (MD)
| | - Zhigao Zhan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yongzhi Yang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yue Miao
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Mei Ding
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
- * E-mail: (LG); (MD)
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9
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Jin EJ, Park S, Lyu X, Jin Y. Gap junctions: historical discoveries and new findings in the Caenorhabditiselegans nervous system. Biol Open 2020; 9:bio053983. [PMID: 32883654 PMCID: PMC7489761 DOI: 10.1242/bio.053983] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Gap junctions are evolutionarily conserved structures at close membrane contacts between two cells. In the nervous system, they mediate rapid, often bi-directional, transmission of signals through channels called innexins in invertebrates and connexins in vertebrates. Connectomic studies from Caenorhabditis elegans have uncovered a vast number of gap junctions present in the nervous system and non-neuronal tissues. The genome also has 25 innexin genes that are expressed in spatial and temporal dynamic pattern. Recent findings have begun to reveal novel roles of innexins in the regulation of multiple processes during formation and function of neural circuits both in normal conditions and under stress. Here, we highlight the diverse roles of gap junctions and innexins in the C. elegans nervous system. These findings contribute to fundamental understanding of gap junctions in all animals.
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Affiliation(s)
- Eugene Jennifer Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Seungmee Park
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Xiaohui Lyu
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
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10
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Shui Y, Liu P, Zhan H, Chen B, Wang ZW. Molecular basis of junctional current rectification at an electrical synapse. SCIENCE ADVANCES 2020; 6:eabb3076. [PMID: 32923588 PMCID: PMC7455501 DOI: 10.1126/sciadv.abb3076] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 05/20/2020] [Indexed: 06/11/2023]
Abstract
Rectifying electrical synapses (RESs) exist across animal species, but their rectification mechanism is largely unknown. We investigated why RESs between AVA premotor interneurons and A-type cholinergic motoneurons (A-MNs) in Caenorhabditis elegans escape circuit conduct junctional currents (I j) only in the antidromic direction. These RESs consist of UNC-7 innexin in AVA and UNC-9 innexin in A-MNs. UNC-7 has multiple isoforms differing in the length and sequence of the amino terminus. In a heterologous expression system, only one UNC-7 isoform, UNC-7b, can form heterotypic gap junctions (GJs) with UNC-9 that strongly favor I j in the UNC-9 to UNC-7 direction. Knockout of unc-7b alone almost eliminated the I j, whereas AVA-specific expression of UNC-7b substantially rescued the coupling defect of unc-7 mutant. Neutralizing charged residues in UNC-7b amino terminus abolished the rectification property of UNC-7b/UNC-9 GJs. Our results suggest that the rectification property results from electrostatic interactions between charged residues in UNC-7b amino terminus.
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Affiliation(s)
- Yuan Shui
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT 06030, USA
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11
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Welzel G, Schuster S. A Direct Comparison of Different Measures for the Strength of Electrical Synapses. Front Cell Neurosci 2019; 13:43. [PMID: 30809130 PMCID: PMC6379294 DOI: 10.3389/fncel.2019.00043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 01/25/2019] [Indexed: 11/13/2022] Open
Abstract
During the last decades it became increasingly evident that electrical synapses are capable of activity-dependent plasticity. However, measuring the actual strength of electrical transmission remains difficult. Usually changes in coupling strength can only be inferred indirectly from measures such as the coupling coefficient and the coupling conductance. Because these are affected by both junctional and non-junctional conductance, plastic changes can potentially be due to both components. Furthermore, these techniques also require the blocking of chemical transmission, so that processes that involve crosstalk between chemical and electrical synapses will be suppressed. To directly examine the magnitude of errors that can occur, we use dual whole-cell current- and voltage-clamp recordings from the soma of the pair of easily accessible, electrically coupled Retzius cells in the leech to simultaneously determine coupling coefficients, coupling conductances and directly measured gap junctional currents. We present the first direct and comparative analysis of gap junction conductance using all three methods and analyze how each method would characterize the response of gap junctions to serotonin. The traditional coupling coefficients showed severe deficits in assessing the symmetry and strength of electrical synapses. These were reduced when coupling conductances were determined and were absent in the direct method. Additionally, both coupling coefficient and coupling conductance caused large and systematic errors in assessing the size and time course of the serotonin-induced changes of gap junctional currents. Most importantly, both measurements can easily be misinterpreted as implying long-term gap junctional plasticity, although the direct measurements confirm its absence. We thus show directly that coupling coefficients and coupling conductances can severely confound plastic changes in membrane and junctional conductance. Wherever possible, voltage clamp measurements should be chosen to accurately characterize the timing and strength of plasticity of electrical synapses. However, we also demonstrate that coupling coefficients can still yield a qualitatively correct picture when amended by independent measurements of the course of membrane resistance during the experiments.
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Affiliation(s)
- Georg Welzel
- Department of Animal Physiology, University of Bayreuth, Bayreuth, Germany
| | - Stefan Schuster
- Department of Animal Physiology, University of Bayreuth, Bayreuth, Germany
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12
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Gap Junctions and NCA Cation Channels Are Critical for Developmentally Timed Sleep and Arousal in Caenorhabditis elegans. Genetics 2018; 210:1369-1381. [PMID: 30323068 DOI: 10.1534/genetics.118.301551] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 10/10/2018] [Indexed: 12/16/2022] Open
Abstract
An essential characteristic of sleep is heightened arousal threshold, with decreased behavioral response to external stimuli. The molecular and cellular mechanisms underlying arousal threshold changes during sleep are not fully understood. We report that loss of UNC-7 or UNC-9 innexin function dramatically reduced sleep and decreased arousal threshold during developmentally timed sleep in Caenorhabditis elegans UNC-7 function was required in premotor interneurons and UNC-9 function was required in motor neurons in this paradigm. Simultaneous transient overexpression of UNC-7 and UNC-9 was sufficient to induce anachronistic sleep in adult animals. Moreover, loss of UNC-7 or UNC-9 suppressed the increased sleep of EGL-4 gain-of-function animals, which have increased cyclic-GMP-dependent protein kinase activity. These results suggest C. elegans gap junctions may act downstream of previously identified sleep regulators. In other paradigms, the NCA cation channels act upstream of gap junctions. Consistent with this, diminished NCA channel activity in C. elegans robustly increased arousal thresholds during sleep bouts in L4-to-adult developmentally timed sleep. Total time in sleep bouts was only modestly increased in animals lacking NCA channel auxiliary subunit UNC-79, whereas increased channel activity dramatically decreased sleep. Loss of EGL-4 or innexin proteins suppressed UNC-79 loss-of-function sleep and arousal defects. In Drosophila, the ion channel narrow abdomen, an ortholog of the C. elegans NCA channels, drive the pigment dispersing factor (PDF) neuropeptide release, regulating circadian behavior. However, in C. elegans, we found that loss of the PDF receptor PDFR-1 did not suppress gain-of-function sleep defects, suggesting an alternative downstream pathway. This study emphasizes the conservation and importance of neuronal activity modulation during sleep, and unequivocally demonstrates that gap junction function is critical for normal sleep.
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13
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Güiza J, Barría I, Sáez JC, Vega JL. Innexins: Expression, Regulation, and Functions. Front Physiol 2018; 9:1414. [PMID: 30364195 PMCID: PMC6193117 DOI: 10.3389/fphys.2018.01414] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 09/18/2018] [Indexed: 01/02/2023] Open
Abstract
The innexin (Inx) proteins form gap junction channels and non-junctional channels (named hemichannels) in invertebrates. These channels participate in cellular communication playing a relevant role in several physiological processes. Pioneer studies conducted mainly in worms and flies have shown that innexins participate in embryo development and behavior. However, recent studies have elucidated new functions of innexins in Arthropoda, Nematoda, Annelida, and Cnidaria, such as immune response, and apoptosis. This review describes emerging data of possible new roles of innexins and summarizes the data available to date.
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Affiliation(s)
- Juan Güiza
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Iván Barría
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile.,Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - José L Vega
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
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14
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Qadota H, Matsunaga Y, Nguyen KCQ, Mattheyses A, Hall DH, Benian GM. High-resolution imaging of muscle attachment structures in Caenorhabditis elegans. Cytoskeleton (Hoboken) 2017; 74:426-442. [PMID: 28921913 DOI: 10.1002/cm.21410] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Revised: 08/18/2017] [Accepted: 09/13/2017] [Indexed: 01/01/2023]
Abstract
We used structured illumination microscopy (SIM) to obtain super-resolution images of muscle attachment structures in Caenorhabditis elegans striated muscle. SIM imaging of M-line components revealed two patterns: PAT-3 (β-integrin) and proteins that interact in a complex with the cytoplasmic tail of β-integrin and localize to the basal muscle cell membrane [UNC-112 (kindlin), PAT-4 (ILK), UNC-97 (PINCH), PAT-6 (α-parvin), and UNC-95], are found in discrete, angled segments with gaps. In contrast, proteins localized throughout the depth of the M-line (UNC-89 (obscurin) and UNC-98) are imaged as continuous lines. Systematic immunostaining of muscle cell boundaries revealed that dense body components close to the basal muscle cell membrane also localize at cell boundaries. SIM imaging of muscle cell boundaries reveal "zipper-like" structures. Electron micrographs reveal electron dense material similar in appearance to dense bodies located adjacent to the basolateral cell membranes of adjacent muscle cells separated by ECM. Moreover, by EM, there are a variety of features of the muscle cell boundaries that help explain the zipper-like pattern of muscle protein localization observed by SIM. Short dense bodies in atn-1 mutants that are null for α-actinin and lack the deeper extensions of dense bodies, showed "zipper-like" structures by SIM similar to cell boundary structures, further indicating that the surface-proximal components of dense bodies form the "zipper-like" structures at cell boundaries. Moreover, mutants in thin and thick filament components do not have "dot-like" dense bodies, suggesting that myofilament tension is required for assembly or maintenance of proper dense body shape.
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Affiliation(s)
- Hiroshi Qadota
- Department of Pathology, Emory University, Atlanta, Georgia 30322
| | - Yohei Matsunaga
- Department of Pathology, Emory University, Atlanta, Georgia 30322
| | - Ken C Q Nguyen
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Alexa Mattheyses
- Department of Cell Biology, Emory University, Atlanta, Georgia 30322
| | - David H Hall
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Guy M Benian
- Department of Pathology, Emory University, Atlanta, Georgia 30322
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15
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Moosavi B, Mousavi B, Yang WC, Yang GF. Yeast-based assays for detecting protein-protein/drug interactions and their inhibitors. Eur J Cell Biol 2017. [PMID: 28645461 DOI: 10.1016/j.ejcb.2017.06.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Understanding cellular processes at molecular levels in health and disease requires the knowledge of protein-protein interactions (PPIs). In line with this, identification of PPIs at genome-wide scale is highly valuable to understand how different cellular pathways are interconnected, and it eventually facilitates designing effective drugs against certain PPIs. Furthermore, investigating PPIs at a small laboratory scale for deciphering certain biochemical pathways has been demanded for years. In this regard, yeast two hybrid system (Y2HS) has proven an extremely useful tool to discover novel PPIs, while Y2HS derivatives and novel yeast-based assays are contributing significantly to identification of protein-drug/inhibitor interaction at both large- and small-scale set-ups. These methods have been evolving over time to provide more accurate, reproducible and quantitative results. Here we briefly describe different yeast-based assays for identification of various protein-protein/drug/inhibitor interactions and their specific applications, advantages, shortcomings, and improvements. The broad range of yeast-based assays facilitates application of the most suitable method(s) for each specific need.
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Affiliation(s)
- Behrooz Moosavi
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, 430079, PR China.
| | - Bibimaryam Mousavi
- Laboratory of Organometallics, Catalysis and Ordered Materials, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Wen-Chao Yang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, 430079, PR China
| | - Guang-Fu Yang
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, 430079, PR China.
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16
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Miller AC, Pereda AE. The electrical synapse: Molecular complexities at the gap and beyond. Dev Neurobiol 2017; 77:562-574. [PMID: 28170151 DOI: 10.1002/dneu.22484] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 01/04/2017] [Accepted: 01/04/2017] [Indexed: 12/21/2022]
Abstract
Gap junctions underlie electrical synaptic transmission between neurons. Generally perceived as simple intercellular channels, "electrical synapses" have demonstrated to be more functionally sophisticated and structurally complex than initially anticipated. Electrical synapses represent an assembly of multiple molecules, consisting of channels, adhesion complexes, scaffolds, regulatory machinery, and trafficking proteins, all required for their proper function and plasticity. Additionally, while electrical synapses are often viewed as strictly symmetric structures, emerging evidence has shown that some components forming electrical synapses can be differentially distributed at each side of the junction. We propose that the molecular complexity and asymmetric distribution of proteins at the electrical synapse provides rich potential for functional diversity. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 562-574, 2017.
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Affiliation(s)
- Adam C Miller
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
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17
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Dissection of neuronal gap junction circuits that regulate social behavior in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2017; 114:E1263-E1272. [PMID: 28143932 DOI: 10.1073/pnas.1621274114] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
A hub-and-spoke circuit of neurons connected by gap junctions controls aggregation behavior and related behavioral responses to oxygen, pheromones, and food in Caenorhabditis elegans The molecular composition of the gap junctions connecting RMG hub neurons with sensory spoke neurons is unknown. We show here that the innexin gene unc-9 is required in RMG hub neurons to drive aggregation and related behaviors, indicating that UNC-9-containing gap junctions mediate RMG signaling. To dissect the circuit in detail, we developed methods to inhibit unc-9-based gap junctions with dominant-negative unc-1 transgenes. unc-1(dn) alters a stomatin-like protein that regulates unc-9 electrical signaling; its disruptive effects can be rescued by a constitutively active UNC-9::GFP protein, demonstrating specificity. Expression of unc-1(dn) in RMG hub neurons, ADL or ASK pheromone-sensing neurons, or URX oxygen-sensing neurons disrupts specific elements of aggregation-related behaviors. In ADL, unc-1(dn) has effects opposite to those of tetanus toxin light chain, separating the roles of ADL electrical and chemical synapses. These results reveal roles of gap junctions in a complex behavior at cellular resolution and provide a tool for similar exploration of other gap junction circuits.
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18
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Meng L, Zhang A, Jin Y, Yan D. Regulation of neuronal axon specification by glia-neuron gap junctions in C. elegans. eLife 2016; 5. [PMID: 27767956 PMCID: PMC5083064 DOI: 10.7554/elife.19510] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 10/20/2016] [Indexed: 01/22/2023] Open
Abstract
Axon specification is a critical step in neuronal development, and the function of glial cells in this process is not fully understood. Here, we show that C. elegans GLR glial cells regulate axon specification of their nearby GABAergic RME neurons through GLR-RME gap junctions. Disruption of GLR-RME gap junctions causes misaccumulation of axonal markers in non-axonal neurites of RME neurons and converts microtubules in those neurites to form an axon-like assembly. We further uncover that GLR-RME gap junctions regulate RME axon specification through activation of the CDK-5 pathway in a calcium-dependent manner, involving a calpain clp-4. Therefore, our study reveals the function of glia-neuron gap junctions in neuronal axon specification and shows that calcium originated from glial cells can regulate neuronal intracellular pathways through gap junctions.
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Affiliation(s)
- Lingfeng Meng
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States.,Department of Neurobiology, Duke University Medical Center, Durham, United States.,Duke Institute for Brain Sciences, Duke Medical Center, Durham, United States
| | - Albert Zhang
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States.,Department of Neurobiology, Duke University Medical Center, Durham, United States.,Duke Institute for Brain Sciences, Duke Medical Center, Durham, United States
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, Howard Hughes Medical Institute, University of California, San Diego, United States.,Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, United States
| | - Dong Yan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, United States.,Department of Neurobiology, Duke University Medical Center, Durham, United States.,Duke Institute for Brain Sciences, Duke Medical Center, Durham, United States
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19
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Meng L, Chen CH, Yan D. Regulation of Gap Junction Dynamics by UNC-44/ankyrin and UNC-33/CRMP through VAB-8 in C. elegans Neurons. PLoS Genet 2016; 12:e1005948. [PMID: 27015090 PMCID: PMC4807823 DOI: 10.1371/journal.pgen.1005948] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 03/01/2016] [Indexed: 11/18/2022] Open
Abstract
Gap junctions are present in both vertebrates and invertebrates from nematodes to mammals. Although the importance of gap junctions has been documented in many biological processes, the molecular mechanisms underlying gap junction dynamics remain unclear. Here, using the C. elegans PLM neurons as a model, we show that UNC-44/ankyrin acts upstream of UNC-33/CRMP in regulation of a potential kinesin VAB-8 to control gap junction dynamics, and loss-of-function in the UNC-44/UNC-33/VAB-8 pathway suppresses the turnover of gap junction channels. Therefore, we first show a signal pathway including ankyrin, CRMP, and kinesin in regulating gap junctions.
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Affiliation(s)
- Lingfeng Meng
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Chia-hui Chen
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
- Department of Neurobiology and Duke Institute for Brain Sciences, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Dong Yan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
- Department of Neurobiology and Duke Institute for Brain Sciences, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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20
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A γ-Secretase Independent Role for Presenilin in Calcium Homeostasis Impacts Mitochondrial Function and Morphology in Caenorhabditis elegans. Genetics 2015; 201:1453-66. [PMID: 26500256 DOI: 10.1534/genetics.115.182808] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Accepted: 10/19/2015] [Indexed: 12/21/2022] Open
Abstract
Mutations in the presenilin (PSEN) encoding genes (PSEN1 and PSEN2) occur in most early onset familial Alzheimer's Disease. Despite the identification of the involvement of PSEN in Alzheimer's Disease (AD) ∼20 years ago, the underlying role of PSEN in AD is not fully understood. To gain insight into the biological function of PSEN, we investigated the role of the PSEN homolog SEL-12 in Caenorhabditis elegans. Using genetic, cell biological, and pharmacological approaches, we demonstrate that mutations in sel-12 result in defects in calcium homeostasis, leading to mitochondrial dysfunction. Moreover, consistent with mammalian PSEN, we provide evidence that SEL-12 has a critical role in mediating endoplasmic reticulum (ER) calcium release. Furthermore, we found that in SEL-12-deficient animals, calcium transfer from the ER to the mitochondria leads to fragmentation of the mitochondria and mitochondrial dysfunction. Additionally, we show that the impact that SEL-12 has on mitochondrial function is independent of its role in Notch signaling, γ-secretase proteolytic activity, and amyloid plaques. Our results reveal a critical role for PSEN in mediating mitochondrial function by regulating calcium transfer from the ER to the mitochondria.
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21
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Necrotic Cells Actively Attract Phagocytes through the Collaborative Action of Two Distinct PS-Exposure Mechanisms. PLoS Genet 2015; 11:e1005285. [PMID: 26061275 PMCID: PMC4464654 DOI: 10.1371/journal.pgen.1005285] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 05/14/2015] [Indexed: 11/19/2022] Open
Abstract
Necrosis, a kind of cell death closely associated with pathogenesis and genetic programs, is distinct from apoptosis in both morphology and mechanism. Like apoptotic cells, necrotic cells are swiftly removed from animal bodies to prevent harmful inflammatory and autoimmune responses. In the nematode Caenorhabditis elegans, gain-of-function mutations in certain ion channel subunits result in the excitotoxic necrosis of six touch neurons and their subsequent engulfment and degradation inside engulfing cells. How necrotic cells are recognized by engulfing cells is unclear. Phosphatidylserine (PS) is an important apoptotic-cell surface signal that attracts engulfing cells. Here we observed PS exposure on the surface of necrotic touch neurons. In addition, the phagocytic receptor CED-1 clusters around necrotic cells and promotes their engulfment. The extracellular domain of CED-1 associates with PS in vitro. We further identified a necrotic cell-specific function of CED-7, a member of the ATP-binding cassette (ABC) transporter family, in promoting PS exposure. In addition to CED-7, anoctamin homolog-1 (ANOH-1), the C. elegans homolog of the mammalian Ca(2+)-dependent phospholipid scramblase TMEM16F, plays an independent role in promoting PS exposure on necrotic cells. The combined activities from CED-7 and ANOH-1 ensure efficient exposure of PS on necrotic cells to attract their phagocytes. In addition, CED-8, the C. elegans homolog of mammalian Xk-related protein 8 also makes a contribution to necrotic cell-removal at the first larval stage. Our work indicates that cells killed by different mechanisms (necrosis or apoptosis) expose a common "eat me" signal to attract their phagocytic receptor(s); furthermore, unlike what was previously believed, necrotic cells actively present PS on their outer surfaces through at least two distinct molecular mechanisms rather than leaking out PS passively.
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22
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Serrano-Velez JL, Rodriguez-Alvarado M, Torres-Vazquez II, Fraser SE, Yasumura T, Vanderpool KG, Rash JE, Rosa-Molinar E. Abundance of gap junctions at glutamatergic mixed synapses in adult Mosquitofish spinal cord neurons. Front Neural Circuits 2014; 8:66. [PMID: 25018700 PMCID: PMC4072101 DOI: 10.3389/fncir.2014.00066] [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: 02/16/2014] [Accepted: 05/28/2014] [Indexed: 11/13/2022] Open
Abstract
"Dye-coupling", whole-mount immunohistochemistry for gap junction channel protein connexin 35 (Cx35), and freeze-fracture replica immunogold labeling (FRIL) reveal an abundance of electrical synapses/gap junctions at glutamatergic mixed synapses in the 14th spinal segment that innervates the adult male gonopodium of Western Mosquitofish, Gambusia affinis (Mosquitofish). To study gap junctions' role in fast motor behavior, we used a minimally-invasive neural-tract-tracing technique to introduce gap junction-permeant or -impermeant dyes into deep muscles controlling the gonopodium of the adult male Mosquitofish, a teleost fish that rapidly transfers (complete in <20 mS) spermatozeugmata into the female reproductive tract. Dye-coupling in the 14th spinal segment controlling the gonopodium reveals coupling between motor neurons and a commissural primary ascending interneuron (CoPA IN) and shows that the 14th segment has an extensive and elaborate dendritic arbor and more gap junctions than do other segments. Whole-mount immunohistochemistry for Cx35 results confirm dye-coupling and show it occurs via gap junctions. Finally, FRIL shows that gap junctions are at mixed synapses and reveals that >50 of the 62 gap junctions at mixed synapses are in the 14th spinal segment. Our results support and extend studies showing gap junctions at mixed synapses in spinal cord segments involved in control of genital reflexes in rodents, and they suggest a link between mixed synapses and fast motor behavior. The findings provide a basis for studies of specific roles of spinal neurons in the generation/regulation of sex-specific behavior and for studies of gap junctions' role in regulating fast motor behavior. Finally, the CoPA IN provides a novel candidate neuron for future studies of gap junctions and neural control of fast motor behaviors.
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Affiliation(s)
| | | | | | - Scott E Fraser
- Molecular and Computational Biology Section, University of Southern California Los Angeles, CA, USA
| | - Thomas Yasumura
- Department of Biomedical Sciences, Colorado State University Fort Collins, CO, USA
| | | | - John E Rash
- Department of Biomedical Sciences, Colorado State University Fort Collins, CO, USA ; Program in Molecular, Cellular and Integrative Neurosciences, Colorado State University Fort Collins, CO, USA
| | - Eduardo Rosa-Molinar
- Biological Imaging Group, University of Puerto Rico San Juan, PR, USA ; Institute of Neurobiology, School of Medicine, University of Puerto Rico San Juan, PR, USA
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23
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Electrical synapses and their functional interactions with chemical synapses. Nat Rev Neurosci 2014; 15:250-63. [PMID: 24619342 DOI: 10.1038/nrn3708] [Citation(s) in RCA: 297] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Brain function relies on the ability of neurons to communicate with each other. Interneuronal communication primarily takes place at synapses, where information from one neuron is rapidly conveyed to a second neuron. There are two main modalities of synaptic transmission: chemical and electrical. Far from functioning independently and serving unrelated functions, mounting evidence indicates that these two modalities of synaptic transmission closely interact, both during development and in the adult brain. Rather than conceiving synaptic transmission as either chemical or electrical, this article emphasizes the notion that synaptic transmission is both chemical and electrical, and that interactions between these two forms of interneuronal communication might be required for normal brain development and function.
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24
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Baker MW, Macagno ER. Control of neuronal morphology and connectivity: Emerging developmental roles for gap junctional proteins. FEBS Lett 2014; 588:1470-9. [DOI: 10.1016/j.febslet.2014.02.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 02/10/2014] [Accepted: 02/12/2014] [Indexed: 11/25/2022]
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25
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Simonsen KT, Moerman DG, Naus CC. Gap junctions in C. elegans. Front Physiol 2014; 5:40. [PMID: 24575048 PMCID: PMC3920094 DOI: 10.3389/fphys.2014.00040] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 01/20/2014] [Indexed: 11/26/2022] Open
Abstract
As in other multicellular organisms, the nematode Caenorhabditis elegans uses gap junctions to provide direct cell-to-cell contact. The nematode gap junctions are formed by innexins (invertebrate analogs of the connexins); a family of proteins that surprisingly share no primary sequence homology, but do share structural and functional similarity with connexins. The model organism C. elegans contains 25 innexin genes and innexins are found in virtually all cell types and tissues. Additionally, many innexins have dynamic expression patterns during development, and several innexins are essential genes in the nematode. C. elegans is a popular invertebrate model due to several features including a simple anatomy, a complete cell lineage, sequenced genome and an array of genetic resources. Thus, the worm has potential to offer valuable insights into the various functions of gap junction mediated intercellular communication.
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Affiliation(s)
- Karina T. Simonsen
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British ColumbiaVancouver, BC, Canada
| | - Donald G. Moerman
- Department of Zoology and Michael Smith Laboratories, University of British ColumbiaVancouver, BC, Canada
| | - Christian C. Naus
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British ColumbiaVancouver, BC, Canada
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26
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Fluorescent protein-based biosensors and their clinical applications. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 113:313-48. [PMID: 23244794 DOI: 10.1016/b978-0-12-386932-6.00008-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Green fluorescent protein and its relatives have shed their light on a wide range of biological problems. To date, with a color palette consisting of fluorescent proteins with different spectra, researchers can "paint" living cells as they desire. Moreover, sophisticated biosensors engineered to contain single or multiple fluorescent proteins, including FRET-based biosensors, spatiotemporally unveil molecular mechanisms underlying physiological processes. Although such molecules have contributed considerably to basic research, their abilities to be used in applied life sciences have yet to be fully explored. Here, we review the molecular bases of fluorescent proteins and fluorescent protein-based biosensors and focus on approaches aimed at applying such proteins to the clinic.
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27
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Liu P, Chen B, Altun ZF, Gross MJ, Shan A, Schuman B, Hall DH, Wang ZW. Six innexins contribute to electrical coupling of C. elegans body-wall muscle. PLoS One 2013; 8:e76877. [PMID: 24130800 PMCID: PMC3793928 DOI: 10.1371/journal.pone.0076877] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 08/29/2013] [Indexed: 11/23/2022] Open
Abstract
C. elegans body-wall muscle cells are electrically coupled through gap junctions. Previous studies suggest that UNC-9 is an important, but not the only, innexin mediating the electrical coupling. Here we analyzed junctional current (Ij) for mutants of additional innexins to identify the remaining innexin(s) important to the coupling. The results suggest that a total of six innexins contribute to the coupling, including UNC-9, INX-1, INX-10, INX-11, INX-16, and INX-18. The Ij deficiency in each mutant was rescued completely by expressing the corresponding wild-type innexin specifically in muscle, suggesting that the innexins function cell-autonomously. Comparisons of Ij between various single, double, and triple mutants suggest that the six innexins probably form two distinct populations of gap junctions with one population consisting of UNC-9 and INX-18 and the other consisting of the remaining four innexins. Consistent with their roles in muscle electrical coupling, five of the six innexins showed punctate localization at muscle intercellular junctions when expressed as GFP- or epitope-tagged proteins, and muscle expression was detected for four of them when assessed by expressing GFP under the control of innexin promoters. The results may serve as a solid foundation for further explorations of structural and functional properties of gap junctions in C. elegans body-wall muscle.
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Affiliation(s)
- Ping Liu
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Bojun Chen
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Zeynep F. Altun
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Maegan J. Gross
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Alan Shan
- Undergraduate Summer Research Internship Program, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - Benjamin Schuman
- Undergraduate Summer Research Internship Program, University of Connecticut Health Center, Farmington, Connecticut, United States of America
| | - David H. Hall
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut, United States of America
- * E-mail:
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28
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Heritable gene knockout in Caenorhabditis elegans by direct injection of Cas9-sgRNA ribonucleoproteins. Genetics 2013; 195:1177-80. [PMID: 23979576 PMCID: PMC3813847 DOI: 10.1534/genetics.113.155853] [Citation(s) in RCA: 218] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We present a novel method of targeted gene disruption that involves direct injection of recombinant Cas9 protein complexed with guide RNA into the gonad of the nematode Caenorhabditis elegans. Biallelic mutants were recovered among the F1 progeny, demonstrating the high efficiency of this method.
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29
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Nagy S, Wright C, Tramm N, Labello N, Burov S, Biron D. A longitudinal study of Caenorhabditis elegans larvae reveals a novel locomotion switch, regulated by G(αs) signaling. eLife 2013; 2:e00782. [PMID: 23840929 PMCID: PMC3699835 DOI: 10.7554/elife.00782] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 05/28/2013] [Indexed: 11/25/2022] Open
Abstract
Despite their simplicity, longitudinal studies of invertebrate models are rare. We thus sought to characterize behavioral trends of Caenorhabditis elegans, from the mid fourth larval stage through the mid young adult stage. We found that, outside of lethargus, animals exhibited abrupt switching between two distinct behavioral states: active wakefulness and quiet wakefulness. The durations of epochs of active wakefulness exhibited non-Poisson statistics. Increased Gαs signaling stabilized the active wakefulness state before, during and after lethargus. In contrast, decreased Gαs signaling, decreased neuropeptide release, or decreased CREB activity destabilized active wakefulness outside of, but not during, lethargus. Taken together, our findings support a model in which protein kinase A (PKA) stabilizes active wakefulness, at least in part through two of its downstream targets: neuropeptide release and CREB. However, during lethargus, when active wakefulness is strongly suppressed, the native role of PKA signaling in modulating locomotion and quiescence may be minor. DOI:http://dx.doi.org/10.7554/eLife.00782.001 The roundworm C. elegans is a key model organism in neuroscience. It has a simple nervous system, made up of just 302 neurons, and was the first multicellular organism to have its genome fully sequenced. The lifecycle of C. elegans begins with an embryonic stage, followed by four larval stages and then adulthood, and worms can progress through this cycle in only three days. However, relatively little is known about how the behaviour of the worms varies across these distinct developmental phases. The body wall of C. elegans contains pairs of muscles that extend along its length, and when waves of muscle contraction travel along its body, the worm undergoes a sinusoidal pattern of movement. A signalling cascade involving a molecule called protein kinase A is thought to help control these movements, and upregulation of this cascade has been shown to increase locomotion. Now, Nagy et al. have analysed the movement of C. elegans during these different stages of development. This involved developing an image processing tool that can analyze the position and posture of a worm’s body in each of three million (or more) images per day. Using this tool, which is called PyCelegans, Nagy et al. identified two behavioral macro-states in one of the larval forms of C. elegans: these states, which can persist for hours, are referred to as active wakefulness and quiet wakefulness. During periods of active wakefulness, the worms spent most (but not all) of their time moving forwards; during quiet wakefulness, they remained largely still. The worms switched abruptly between these two states, and the transition seemed to be regulated by PKA signaling. By using PyCelegans to compare locomotion in worms with mutations in genes encoding various components of this pathway, Nagy et al. showed that mutants with increased PKA activity spent more time in a state of active wakefulness, while the opposite was true for worms with mutations that reduced PKA activity. In addition to providing new insights into the control of locomotion in C. elegans, this study has provided a new open-source PyCelegans suite of tools, which are available to be extended and adapted by other researchers for new uses. DOI:http://dx.doi.org/10.7554/eLife.00782.002
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Affiliation(s)
- Stanislav Nagy
- Institute for Biophysical Dynamics, University of Chicago , Chicago , United States
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30
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Philbrook A, Barbagallo B, Francis MM. A tale of two receptors: Dual roles for ionotropic acetylcholine receptors in regulating motor neuron excitation and inhibition. WORM 2013; 2:e25765. [PMID: 24778941 PMCID: PMC3875653 DOI: 10.4161/worm.25765] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Accepted: 07/15/2013] [Indexed: 11/29/2022]
Abstract
Nicotinic or ionotropic acetylcholine receptors (iAChRs) mediate excitatory signaling throughout the nervous system, and the heterogeneity of these receptors contributes to their multifaceted roles. Our recent work has characterized a single iAChR subunit, ACR-12, which contributes to two distinct iAChR subtypes within the C. elegans motor circuit. These two receptor subtypes regulate the coordinated activity of excitatory (cholinergic) and inhibitory (GABAergic) motor neurons. We have shown that the iAChR subunit ACR-12 is differentially expressed in both cholinergic and GABAergic motor neurons within the motor circuit. In cholinergic motor neurons, ACR-12 is incorporated into the previously characterized ACR-2 heteromeric receptor, which shows non-synaptic localization patterns and plays a modulatory role in controlling circuit function.1 In contrast, a second population of ACR-12-containing receptors in GABAergic motor neurons, ACR-12GABA, shows synaptic expression and regulates inhibitory signaling.2 Here, we discuss the two ACR-12-containing receptor subtypes, their distinct expression patterns, and functional roles in the C. elegans motor circuit. We anticipate our continuing studies of iAChRs in the C. elegans motor circuit will lead to novel insights into iAChR function in the nervous system as well as mechanisms for their regulation.
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Affiliation(s)
- Alison Philbrook
- Department of Neurobiology; UMass Medical School; Worcester, MA USA
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31
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Zhang J, Li X, Jevince AR, Guan L, Wang J, Hall DH, Huang X, Ding M. Neuronal target identification requires AHA-1-mediated fine-tuning of Wnt signaling in C. elegans. PLoS Genet 2013; 9:e1003618. [PMID: 23825972 PMCID: PMC3694823 DOI: 10.1371/journal.pgen.1003618] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 05/23/2013] [Indexed: 11/29/2022] Open
Abstract
Electrical synaptic transmission through gap junctions is a vital mode of intercellular communication in the nervous system. The mechanism by which reciprocal target cells find each other during the formation of gap junctions, however, is poorly understood. Here we show that gap junctions are formed between BDU interneurons and PLM mechanoreceptors in C. elegans and the connectivity of BDU with PLM is influenced by Wnt signaling. We further identified two PAS-bHLH family transcription factors, AHA-1 and AHR-1, which function cell-autonomously within BDU and PLM to facilitate the target identification process. aha-1 and ahr-1 act genetically upstream of cam-1. CAM-1, a membrane-bound receptor tyrosine kinase, is present on both BDU and PLM cells and likely serves as a Wnt antagonist. By binding to a cis-regulatory element in the cam-1 promoter, AHA-1 enhances cam-1 transcription. Our study reveals a Wnt-dependent fine-tuning mechanism that is crucial for mutual target cell identification during the formation of gap junction connections. The establishment of functional neuronal circuits requires that different neurons respond selectively to guidance molecules at particular times and in specific locations. In the target region, where cells connect, the same guidance molecules steer the growth of neurites from both the neuron and its target cell. The spatial, temporal, and cell-type-specific regulation of neuronal connection needs to be tightly regulated and precisely coordinated within the neuron and its target cell to achieve effective connection. In this study, we found that the precise connectivity of the BDU interneuron and the PLM mechanoreceptor in the nematode worm Caenorhabditis elegans is influenced by Wnt signaling. BDU-PLM contact also depends on the transcription factor AHA-1, which functions within both BDU and PLM cells to enhance transcription of the gene encoding the trans-membrane receptor CAM-1. CAM-1 is present on BDU and PLM and likely serves as a Wnt antagonist, thus linking transcriptional regulation by AHA-1 to modulation of Wnt signaling. Therefore, our study reveals a locally confined, cell type-specific and cell-autonomous mechanism that mediates mutual target identification.
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Affiliation(s)
- Jingyan Zhang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xia Li
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Angela R. Jevince
- Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Liying Guan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Jiaming Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - David H. Hall
- Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- * E-mail: (XH); (MD)
| | - Mei Ding
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- * E-mail: (XH); (MD)
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Izquierdo EJ, Beer RD. Connecting a connectome to behavior: an ensemble of neuroanatomical models of C. elegans klinotaxis. PLoS Comput Biol 2013; 9:e1002890. [PMID: 23408877 PMCID: PMC3567170 DOI: 10.1371/journal.pcbi.1002890] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 12/03/2012] [Indexed: 11/23/2022] Open
Abstract
Increased efforts in the assembly and analysis of connectome data are providing new insights into the principles underlying the connectivity of neural circuits. However, despite these considerable advances in connectomics, neuroanatomical data must be integrated with neurophysiological and behavioral data in order to obtain a complete picture of neural function. Due to its nearly complete wiring diagram and large behavioral repertoire, the nematode worm Caenorhaditis elegans is an ideal organism in which to explore in detail this link between neural connectivity and behavior. In this paper, we develop a neuroanatomically-grounded model of salt klinotaxis, a form of chemotaxis in which changes in orientation are directed towards the source through gradual continual adjustments. We identify a minimal klinotaxis circuit by systematically searching the C. elegans connectome for pathways linking chemosensory neurons to neck motor neurons, and prune the resulting network based on both experimental considerations and several simplifying assumptions. We then use an evolutionary algorithm to find possible values for the unknown electrophsyiological parameters in the network such that the behavioral performance of the entire model is optimized to match that of the animal. Multiple runs of the evolutionary algorithm produce an ensemble of such models. We analyze in some detail the mechanisms by which one of the best evolved circuits operates and characterize the similarities and differences between this mechanism and other solutions in the ensemble. Finally, we propose a series of experiments to determine which of these alternatives the worm may be using.
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Wang R, Mellem JE, Jensen M, Brockie PJ, Walker CS, Hoerndli FJ, Hauth L, Madsen DM, Maricq AV. The SOL-2/Neto auxiliary protein modulates the function of AMPA-subtype ionotropic glutamate receptors. Neuron 2012; 75:838-50. [PMID: 22958824 DOI: 10.1016/j.neuron.2012.06.038] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/29/2012] [Indexed: 11/30/2022]
Abstract
The neurotransmitter glutamate mediates excitatory synaptic transmission by gating ionotropic glutamate receptors (iGluRs). AMPA receptors (AMPARs), a subtype of iGluR, are strongly implicated in synaptic plasticity, learning, and memory. We previously discovered two classes of AMPAR auxiliary proteins in C. elegans that modify receptor kinetics and thus change synaptic transmission. Here, we have identified another auxiliary protein, SOL-2, a CUB-domain protein that associates with both the related auxiliary subunit SOL-1 and with the GLR-1 AMPAR. In sol-2 mutants, behaviors dependent on glutamatergic transmission are disrupted, GLR-1-mediated currents are diminished, and GLR-1 desensitization and pharmacology are modified. Remarkably, a secreted variant of SOL-1 delivered in trans can rescue sol-1 mutants, and this rescue depends on in cis expression of SOL-2. Finally, we demonstrate that SOL-1 and SOL-2 have an ongoing role in the adult nervous system to control AMPAR-mediated currents.
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Affiliation(s)
- Rui Wang
- Department of Biology, University of Utah, Salt Lake City, UT 84112-0840, USA
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34
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Diversity in genetic in vivo methods for protein-protein interaction studies: from the yeast two-hybrid system to the mammalian split-luciferase system. Microbiol Mol Biol Rev 2012; 76:331-82. [PMID: 22688816 DOI: 10.1128/mmbr.05021-11] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The yeast two-hybrid system pioneered the field of in vivo protein-protein interaction methods and undisputedly gave rise to a palette of ingenious techniques that are constantly pushing further the limits of the original method. Sensitivity and selectivity have improved because of various technical tricks and experimental designs. Here we present an exhaustive overview of the genetic approaches available to study in vivo binary protein interactions, based on two-hybrid and protein fragment complementation assays. These methods have been engineered and employed successfully in microorganisms such as Saccharomyces cerevisiae and Escherichia coli, but also in higher eukaryotes. From single binary pairwise interactions to whole-genome interactome mapping, the self-reassembly concept has been employed widely. Innovative studies report the use of proteins such as ubiquitin, dihydrofolate reductase, and adenylate cyclase as reconstituted reporters. Protein fragment complementation assays have extended the possibilities in protein-protein interaction studies, with technologies that enable spatial and temporal analyses of protein complexes. In addition, one-hybrid and three-hybrid systems have broadened the types of interactions that can be studied and the findings that can be obtained. Applications of these technologies are discussed, together with the advantages and limitations of the available assays.
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Stomatin inhibits pannexin-1-mediated whole-cell currents by interacting with its carboxyl terminal. PLoS One 2012; 7:e39489. [PMID: 22768083 PMCID: PMC3387187 DOI: 10.1371/journal.pone.0039489] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 05/21/2012] [Indexed: 12/20/2022] Open
Abstract
The pannexin-1 (Panx1) channel (often referred to as the Panx1 hemichannel) is a large-conductance channel in the plasma membrane of many mammalian cells. While opening of the channel is potentially detrimental to the cell, little is known about how it is regulated under physiological conditions. Here we show that stomatin inhibited Panx1 channel activity. In transfected HEK-293 cells, stomatin reduced Panx1-mediated whole-cell currents without altering either the total or membrane surface Panx1 protein expression. Stomatin coimmunoprecipitated with full-length Panx1 as well as a Panx1 fragment containing the fourth membrane-spanning domain and the cytosolic carboxyl terminal. The inhibitory effect of stomatin on Panx1-mediated whole-cell currents was abolished by truncating Panx1 at a site in the cytosolic carboxyl terminal. In primary culture of mouse astrocytes, inhibition of endogenous stomatin expression by small interfering RNA enhanced Panx1-mediated outward whole-cell currents. These observations suggest that stomatin may play important roles in astrocytes and other cells by interacting with Panx1 carboxyl terminal to limit channel opening.
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36
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Goodman MB, Lindsay TH, Lockery SR, Richmond JE. Electrophysiological methods for Caenorhabditis elegans neurobiology. Methods Cell Biol 2012; 107:409-36. [PMID: 22226532 DOI: 10.1016/b978-0-12-394620-1.00014-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Patch-clamp electrophysiology is a technique of choice for the biophysical analysis of the function of nerve, muscle, and synapse in Caenorhabditis elegans nematodes. Considerable technical progress has been made in C. elegans electrophysiology in the decade since the initial publication of this technique. Today, most, if not all, electrophysiological studies that can be done in larger animal preparations can also be done in C. elegans. This chapter has two main goals. The first is to present to a broad audience the many techniques available for patch-clamp analysis of neurons, muscles, and synapses in C. elegans. The second is to provide a methodological introduction to the techniques for patch clamping C. elegans neurons and body-wall muscles in vivo, including emerging methods for optogenetic stimulation coupled with postsynaptic recording. We also present samples of the cell-intrinsic and postsynaptic ionic currents that can be measured in C. elegans nerves and muscles.
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Affiliation(s)
- Miriam B Goodman
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California, USA
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Liu P, Chen B, Wang ZW. Gap junctions synchronize action potentials and Ca2+ transients in Caenorhabditis elegans body wall muscle. J Biol Chem 2011; 286:44285-44293. [PMID: 22033926 PMCID: PMC3243499 DOI: 10.1074/jbc.m111.292078] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 10/25/2011] [Indexed: 11/06/2022] Open
Abstract
The sinusoidal locomotion of Caenorhabditis elegans requires synchronous activities of neighboring body wall muscle cells. However, it is unknown whether the synchrony results from muscle electrical coupling or neural inputs. We analyzed the effects of mutating gap junction proteins and blocking neuromuscular transmission on the synchrony of action potentials (APs) and Ca2+ transients among neighboring body wall muscle cells. In wild-type worms, the percentage of synchronous APs between two neighboring cells varied depending on the anatomical relationship and junctional conductance (Gj) between them, and Ca2+ transients were synchronous among neighboring muscle cells. Compared with the wild type, knock-out of the gap junction gene unc-9 resulted in greatly reduced coupling coefficient and asynchronous APs and Ca2+ transients. Inhibition of unc-9 expression specifically in muscle by RNAi also reduced the synchrony of APs and Ca2+ transients, whereas expression of wild-type UNC-9 specifically in muscle rescued the synchrony defect. Loss of the stomatin-like protein UNC-1, which is a regulator of UNC-9-based gap junctions, similarly impaired muscle synchrony as unc-9 mutant did. The blockade of muscle ionotropic acetylcholine receptors by (+)-tubocurarine decreased the frequencies of APs and Ca2+ transients, whereas blockade of muscle GABAA receptors by gabazine had opposite effects. However, both APs and Ca2+ transients remained synchronous after the application of (+)-tubocurarine and/or gabazine. These observations suggest that gap junctions in C. elegans body wall muscle cells are responsible for synchronizing muscle APs and Ca2+ transients.
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Affiliation(s)
- Ping 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
| | - Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030.
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38
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Abstract
The appearance of multicellular organisms imposed the development of several mechanisms for cell-to-cell communication, whereby different types of cells coordinate their function. Some of these mechanisms depend on the intercellular diffusion of signal molecules in the extracellular spaces, whereas others require cell-to-cell contact. Among the latter mechanisms, those provided by the proteins of the connexin family are widespread in most tissues. Connexin signaling is achieved via direct exchanges of cytosolic molecules between adjacent cells at gap junctions, for cell-to-cell coupling, and possibly also involves the formation of membrane "hemi-channels," for the extracellular release of cytosolic signals, direct interactions between connexins and other cell proteins, and coordinated influence on the expression of multiple genes. Connexin signaling appears to be an obligatory attribute of all multicellular exocrine and endocrine glands. Specifically, the experimental evidence we review here points to a direct participation of the Cx36 isoform in the function of the insulin-producing β-cells of the endocrine pancreas, and of the Cx40 isoform in the function of the renin-producing juxtaglomerular epithelioid cells of the kidney cortex.
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Affiliation(s)
- Domenico Bosco
- Department of Surgery, University of Geneva Medical School, Geneva, Switzerland
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39
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Newman RH, Fosbrink MD, Zhang J. Genetically encodable fluorescent biosensors for tracking signaling dynamics in living cells. Chem Rev 2011; 111:3614-66. [PMID: 21456512 PMCID: PMC3092831 DOI: 10.1021/cr100002u] [Citation(s) in RCA: 260] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Robert H. Newman
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Matthew D. Fosbrink
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Jin Zhang
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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40
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Liu Y, LeBeouf B, Guo X, Correa PA, Gualberto DG, Lints R, Garcia LR. A cholinergic-regulated circuit coordinates the maintenance and bi-stable states of a sensory-motor behavior during Caenorhabditis elegans male copulation. PLoS Genet 2011; 7:e1001326. [PMID: 21423722 PMCID: PMC3053324 DOI: 10.1371/journal.pgen.1001326] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 02/04/2011] [Indexed: 11/18/2022] Open
Abstract
Penetration of a male copulatory organ into a suitable mate is a conserved and necessary behavioral step for most terrestrial matings; however, the detailed molecular and cellular mechanisms for this distinct social interaction have not been elucidated in any animal. During mating, the Caenorhabditis elegans male cloaca is maintained over the hermaphrodite's vulva as he attempts to insert his copulatory spicules. Rhythmic spicule thrusts cease when insertion is sensed. Circuit components consisting of sensory/motor neurons and sex muscles for these steps have been previously identified, but it was unclear how their outputs are integrated to generate a coordinated behavior pattern. Here, we show that cholinergic signaling between the cloacal sensory/motor neurons and the posterior sex muscles sustains genital contact between the sexes. Simultaneously, via gap junctions, signaling from these muscles is transmitted to the spicule muscles, thus coupling repeated spicule thrusts with vulval contact. To transit from rhythmic to sustained muscle contraction during penetration, the SPC sensory-motor neurons integrate the signal of spicule's position in the vulva with inputs from the hook and cloacal sensilla. The UNC-103 K(+) channel maintains a high excitability threshold in the circuit, so that sustained spicule muscle contraction is not stimulated by fewer inputs. We demonstrate that coordination of sensory inputs and motor outputs used to initiate, maintain, self-monitor, and complete an innate behavior is accomplished via the coupling of a few circuit components.
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Affiliation(s)
- Yishi Liu
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Brigitte LeBeouf
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- Howard Hughes Medical Institute, Texas A&M University, College Station, Texas, United States of America
| | - Xiaoyan Guo
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Paola A. Correa
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Daisy G. Gualberto
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- Howard Hughes Medical Institute, Texas A&M University, College Station, Texas, United States of America
| | - Robyn Lints
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - L. Rene Garcia
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- Howard Hughes Medical Institute, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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41
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Hudry B, Viala S, Graba Y, Merabet S. Visualization of protein interactions in living Drosophila embryos by the bimolecular fluorescence complementation assay. BMC Biol 2011; 9:5. [PMID: 21276241 PMCID: PMC3041725 DOI: 10.1186/1741-7007-9-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Accepted: 01/28/2011] [Indexed: 01/06/2023] Open
Abstract
Background Protein interactions control the regulatory networks underlying developmental processes. The understanding of developmental complexity will, therefore, require the characterization of protein interactions within their proper environment. The bimolecular fluorescence complementation (BiFC) technology offers this possibility as it enables the direct visualization of protein interactions in living cells. However, its potential has rarely been applied in embryos of animal model organisms and was only performed under transient protein expression levels. Results Using a Hox protein partnership as a test case, we investigated the suitability of BiFC for the study of protein interactions in the living Drosophila embryo. Importantly, all BiFC parameters were established with constructs that were stably expressed under the control of endogenous promoters. Under these physiological conditions, we showed that BiFC is specific and sensitive enough to analyse dynamic protein interactions. We next used BiFC in a candidate interaction screen, which led to the identification of several Hox protein partners. Conclusion Our results establish the general suitability of BiFC for revealing and studying protein interactions in their physiological context during the rapid course of Drosophila embryonic development.
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Affiliation(s)
- Bruno Hudry
- Institut de Biologie du Développement de Marseille Luminy, IBDML, UMR 6216, CNRS, Université de la méditerranée, Parc Scientifique de Luminy, Case 907, 13288, Marseille Cedex 09, France
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Abstract
The BK channel is a Ca²+- and voltage-gated potassium channel with many important physiological functions. To identify proteins important to its function in vivo, we screened for Caenorhabditis elegans mutants that suppressed a lethargic phenotype caused by expressing a gain-of-function (gf) isoform of the BK channel α-subunit SLO-1. BKIP-1 (for BK channel interacting protein), a small peptide with no significant homology to any previously characterized molecules, was thus identified. BKIP-1 and SLO-1 showed similar expression and subcellular localization patterns and appeared to interact physically through discrete domains. bkip-1 loss-of-function (lf) mutants phenocopied slo-1(lf) mutants in behavior and synaptic transmission and suppressed the lethargy, egg-laying defect, and deficient neurotransmitter release caused by SLO-1(gf). In heterologous expression systems, BKIP-1 decreased the activation rate and shifted the conductance-voltage relationship of SLO-1 in a Ca²+-dependent manner and increased SLO-1 surface expression. Thus, BKIP-1 is a novel auxiliary subunit critical to SLO-1 function in vivo.
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43
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Wang ZW. Origin of quantal size variation and high-frequency miniature postsynaptic currents at the Caenorhabditis elegans neuromuscular junction. J Neurosci Res 2010; 88:3425-32. [PMID: 20722072 PMCID: PMC3058485 DOI: 10.1002/jnr.22468] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Revised: 04/26/2010] [Accepted: 06/20/2010] [Indexed: 11/08/2022]
Abstract
The neuromuscular junction (NMJ) of Caenorhabditis elegans has proved to be a very useful model synapse for investigating molecular mechanisms of synaptic transmission. Intriguingly, miniature postsynaptic currents (minis) at this synapse occur at an unusually high frequency (50-90 Hz in wild-type worms) and show large variation in quantal size (from <10 pA to >200 pA). It is important to understand the cellular and molecular bases for these properties of minis in order to interpret electrophysiological data from this synapse properly. Existing data suggest that several factors may contribute to the high frequency and quantal size variation, including 1) the establishment of multiple NMJs with each body-wall muscle cell, 2) diversity of postsynaptic receptors (two acetylcholine receptors and one GABA receptor), 3) association of one presynaptic site with several body-wall muscle cells, 4) effects of Ca(2+) at the presynaptic site, and 5) a possibly elevated (less negative) resting membrane potential in motoneurons. Neither the frequency nor the quantal size of minis is affected by electrical coupling of body-wall muscle cells. Furthermore, quantal size variation is not due to synchronized multivesicular release. Analyses of the C. elegans NMJ may lead to a better understanding of the mechanisms controlling the frequency and quantal size of minis of other synapses as well.
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Affiliation(s)
- Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030-3401, USA.
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44
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α-Catulin CTN-1 is required for BK channel subcellular localization in C. elegans body-wall muscle cells. EMBO J 2010; 29:3184-95. [PMID: 20700105 DOI: 10.1038/emboj.2010.194] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Accepted: 07/20/2010] [Indexed: 11/09/2022] Open
Abstract
The BK channel, a voltage- and Ca(2+)-gated large-conductance potassium channel with many important functions, is often localized at specific subcellular domains. Although proper subcellular localization is likely a prerequisite for the channel to perform its physiological functions, little is known about the molecular basis of localization. Here, we show that CTN-1, a homologue of mammalian α-catulin, is required for subcellular localization of SLO-1, the Caenorhabditis elegans BK channel α-subunit, in body-wall muscle cells. CTN-1 was identified in a genetic screen for mutants that suppressed a lethargic phenotype caused by expressing a gain-of-function (gf) isoform of SLO-1. In body-wall muscle cells, CTN-1 coclusters with SLO-1 at regions of dense bodies, which are Z-disk analogs of mammalian skeletal muscle. In ctn-1 loss-of-function (lf) mutants, SLO-1 was mislocalized in body-wall muscle but its transcription and protein level were unchanged. Targeted rescue of ctn-1(lf) in muscle was sufficient to reinstate the lethargic phenotype in slo-1(gf);ctn-1(lf). These results suggest that CTN-1 plays an important role in BK channel function by mediating channel subcellular localization.
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45
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Gonçalves SA, Matos JE, Outeiro TF. Zooming into protein oligomerization in neurodegeneration using BiFC. Trends Biochem Sci 2010; 35:643-51. [PMID: 20561791 DOI: 10.1016/j.tibs.2010.05.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 05/10/2010] [Accepted: 05/13/2010] [Indexed: 11/25/2022]
Abstract
Several neurodegenerative diseases are characterized by the accumulation of misfolded and aggregated proteins, which lead to neurotoxicity. However, the nature of those toxic species is controversial. Developments in optical microscopy and live-cell imaging are essential in providing crucial insight into the molecular mechanisms involved. In particular, the technique of bimolecular fluorescence complementation (BiFC) represents a remarkable improvement for observing protein-protein interactions within living cells. Unlike other techniques, BiFC provides spatial and temporal resolution and can be carried out in a physiological environment. Among other applications, BiFC has been used to study molecular determinants of oligomerization in neurodegenerative disorders, thereby promising to unveil novel targets for therapeutics. We review the applicability of BiFC for investigating the molecular basis of neurodegenerative diseases associated with protein misfolding and aggregation.
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Affiliation(s)
- Susana A Gonçalves
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
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46
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Almedom RB, Liewald JF, Hernando G, Schultheis C, Rayes D, Pan J, Schedletzky T, Hutter H, Bouzat C, Gottschalk A. An ER-resident membrane protein complex regulates nicotinic acetylcholine receptor subunit composition at the synapse. EMBO J 2009; 28:2636-49. [PMID: 19609303 PMCID: PMC2738700 DOI: 10.1038/emboj.2009.204] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Accepted: 06/18/2009] [Indexed: 11/09/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are homo- or heteropentameric ligand-gated ion channels mediating excitatory neurotransmission and muscle activation. Regulation of nAChR subunit assembly and transfer of correctly assembled pentamers to the cell surface is only partially understood. Here, we characterize an ER transmembrane (TM) protein complex that influences nAChR cell-surface expression and functional properties in Caenorhabditis elegans muscle. Loss of either type I TM protein, NRA-2 or NRA-4 (nicotinic receptor associated), affects two different types of muscle nAChRs and causes in vivo resistance to cholinergic agonists. Sensitivity to subtype-specific agonists of these nAChRs is altered differently, as demonstrated by whole-cell voltage-clamp of dissected adult muscle, when applying exogenous agonists or after photo-evoked, channelrhodopsin-2 (ChR2) mediated acetylcholine (ACh) release, as well as in single-channel recordings in cultured embryonic muscle. These data suggest that nAChRs desensitize faster in nra-2 mutants. Cell-surface expression of different subunits of the 'levamisole-sensitive' nAChR (L-AChR) is differentially affected in the absence of NRA-2 or NRA-4, suggesting that they control nAChR subunit composition or allow only certain receptor assemblies to leave the ER.
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Affiliation(s)
- Ruta B Almedom
- Department of Biochemistry, Chemistry and Pharmacy, Johann Wolfgang Goethe-University, Institute of Biochemistry, Frankfurt, Germany
| | - Jana F Liewald
- Department of Biochemistry, Chemistry and Pharmacy, Johann Wolfgang Goethe-University, Institute of Biochemistry, Frankfurt, Germany
| | - Guillermina Hernando
- Instituto de Investigaciones Bioquimicas, Universidad Nacional del Sur-CONICET, Bahia Blanca, Argentina
| | - Christian Schultheis
- Department of Biochemistry, Chemistry and Pharmacy, Johann Wolfgang Goethe-University, Institute of Biochemistry, Frankfurt, Germany
| | - Diego Rayes
- Instituto de Investigaciones Bioquimicas, Universidad Nacional del Sur-CONICET, Bahia Blanca, Argentina
| | - Jie Pan
- Department of Biological Sciences, Simon Fraser University, University Drive, Burnaby, British Columbia, Canada
| | - Thorsten Schedletzky
- Department of Biochemistry, Chemistry and Pharmacy, Johann Wolfgang Goethe-University, Institute of Biochemistry, Frankfurt, Germany
| | - Harald Hutter
- Department of Biological Sciences, Simon Fraser University, University Drive, Burnaby, British Columbia, Canada
| | - Cecilia Bouzat
- Instituto de Investigaciones Bioquimicas, Universidad Nacional del Sur-CONICET, Bahia Blanca, Argentina
| | - Alexander Gottschalk
- Department of Biochemistry, Chemistry and Pharmacy, Johann Wolfgang Goethe-University, Institute of Biochemistry, Frankfurt, Germany
- Cluster of Excellence Frankfurt—Macromolecular Complexes (CEF-MC), Goethe-University, Frankfurt, Germany
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Abstract
In a genetic screen for active zone defective mutants in Caenorhabditis elegans, we isolated a loss-of-function allele of unc-7, a gene encoding an innexin/pannexin family gap junction protein. Innexin UNC-7 regulates the size and distribution of active zones at C. elegans neuromuscular junctions. Loss-of-function mutations in another innexin, UNC-9, cause similar active zone defects as unc-7 mutants. In addition to presumptive gap junction localizations, both UNC-7 and UNC-9 are also localized perisynaptically throughout development and required in presynaptic neurons to regulate active zone differentiation. Our mosaic analyses, electron microscopy, as well as expression studies suggest a novel and likely nonjunctional role of specific innexins in active zone differentiation in addition to gap junction formations.
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Starich TA, Xu J, Skerrett IM, Nicholson BJ, Shaw JE. Interactions between innexins UNC-7 and UNC-9 mediate electrical synapse specificity in the Caenorhabditis elegans locomotory nervous system. Neural Dev 2009; 4:16. [PMID: 19432959 PMCID: PMC2694797 DOI: 10.1186/1749-8104-4-16] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Accepted: 05/11/2009] [Indexed: 11/10/2022] Open
Abstract
Background Approximately 10% of Caenorhabditis elegans nervous system synapses are electrical, that is, gap junctions composed of innexins. The locomotory nervous system consists of several pairs of interneurons and three major classes of motor neurons, all with stereotypical patterns of connectivity that include gap junctions. Mutations in the two innexin genes unc-7 and unc-9 result in identical uncoordinated movement phenotypes, and their respective gene products were investigated for their contribution to electrical synapse connectivity. Results unc-7 encodes three innexin isoforms. Two of these, UNC-7S and UNC-7SR, are functionally equivalent and play an essential role in coordinated locomotion. UNC-7S and UNC-7SR are widely expressed and co-localize extensively with green fluorescent protein-tagged innexin UNC-9 in the ventral and dorsal nerve cords. A subset of UNC-7S/SR expression visualizes gap junctions formed between the AVB forward command interneurons and their B class motor neuron partners. Experiments indicate that expression of UNC-7S/SR in AVB and expression of UNC-9 in B motor neurons is necessary for these gap junctions to form. In Xenopus oocyte pairs, both UNC-7S and UNC-9 form homomeric gap junctions, and together they form heterotypic channels. Xenopus oocyte studies and co-localization studies in C. elegans suggest that UNC-7S and UNC-9 do not heteromerize in the same hemichannel, leading to the model that hemichannels in AVB:B motor neuron gap junctions are homomeric and heterotypic. Conclusion UNC-7S and UNC-9 are widely expressed and contribute to a large number of the gap junctions identified in the locomotory nervous system. Proper AVB:B gap junction formation requires UNC-7S expression in AVB interneurons and UNC-9 expression in B motor neurons. More broadly, this illustrates that innexin identity is critical for electrical synapse specificity, but differential (compartmentalized) innexin expression cannot account for all of the specificity seen in C. elegans, and other factors must influence the determination of synaptic partners.
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Affiliation(s)
- Todd A Starich
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55406, USA.
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Morell M, Ventura S, Avilés FX. Protein complementation assays: Approaches for the in vivo analysis of protein interactions. FEBS Lett 2009; 583:1684-91. [DOI: 10.1016/j.febslet.2009.03.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Accepted: 03/02/2009] [Indexed: 11/28/2022]
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50
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Shyu YJ, Hiatt SM, Duren HM, Ellis RE, Kerppola TK, Hu CD. Visualization of protein interactions in living Caenorhabditis elegans using bimolecular fluorescence complementation analysis. Nat Protoc 2008; 3:588-96. [PMID: 18388940 DOI: 10.1038/nprot.2008.16] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The bimolecular fluorescence complementation (BiFC) assay is a powerful tool for visualizing and identifying protein interactions in living cells. This assay is based on the principle of protein-fragment complementation, using two nonfluorescent fragments derived from fluorescent proteins. When two fragments are brought together in living cells by tethering each to one of a pair of interacting proteins, fluorescence is restored. Here, we provide a protocol for a Venus-based BiFC assay to visualize protein interactions in the living nematode, Caenorhabditis elegans. We discuss how to design appropriate C. elegans BiFC cloning vectors to enable visualization of protein interactions using either inducible heat shock promoters or native promoters; transform the constructs into worms by microinjection; and analyze and interpret the resulting data. When expression of BiFC fusion proteins is induced by heat shock, the fluorescent signals can be visualized as early as 30 min after induction and last for 24 h in transgenic animals. The entire procedure takes 2-3 weeks to complete.
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Affiliation(s)
- Y John Shyu
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-2091, USA
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