500+ Papers found (0.024 seconds)

Choi, U. et al. (2019) International Worm Meeting "The head mesodermal cell (HMC) controls aBoc."

[

International Worm Meeting,

2019]

The head mesodermal cell (HMC) resides next to the terminal bulb of the pharynx in the head and has no reported function. HMC projects several long branching processes from the cell body that form gap junctions with the neck muscles and that are in contact with the pseudocoelom. The anterior body muscle contraction (aBoc) is one of three robust sequential muscle contractions that make up the defecation motor program (DMP), a pacemaker-controlled rhythmic behavior that functions to expel digested food from the intestine. aBoc occurs when the timing messenger, NLP-40, is released from the pacemaker (intestine) and binds its receptor AEX-2 on AVL motor neurons leading to their transient activation and release of the FMRF-like neuropeptide, FLP-22 from AVL axons. In screens for downstream targets of FLP-22, we identified the GPCR FRPR-17. Both frpr-17 and flp-22 null mutants exhibit identical defects in aBoc, but have no defects in the other muscle contractions of the DMP. frpr-17 mutations do not enhance the aBoc effects of flp-22 mutants and completely suppress the muscle hypercontraction defects caused by FLP-22 overexpression. Tissue-specific rescue experiments reveal that frpr-17 functions in HMC, but not in neurons or in muscles to promote aBoc. In vivo calcium live imaging using GCaMP6 expressed in HMC reveals that HMC is rhythmically activated every 50 seconds, and that each calcium transient occurs about three seconds after the start of the cycle and coincides with the aBoc contraction. Together, these results suggest that HMC functions as the target for neuroendocrine signaling in the circuit that controls aBoc. We propose that HMC functions to control aBoc by promoting neck muscle contraction via gap junctions following its activation by FLP-22/FRPR-17 signaling.

Choi U et al. (2023) Nat Commun "The head mesodermal cell couples FMRFamide neuropeptide signaling with rhythmic muscle contraction in C. elegans."

Zhang Q, Sieburth D, Hu M, Choi U

[

Nat Commun,

2023]

FMRFamides are evolutionarily conserved neuropeptides that play critical roles in behavior, energy balance, and reproduction. Here, we show that FMRFamide signaling from the nervous system is critical for the rhythmic activation of a single cell of previously unknown function, the head mesodermal cell (hmc) in C. elegans. Behavioral, calcium imaging, and genetic studies reveal that release of the FLP-22 neuropeptide from the AVL neuron in response to pacemaker signaling activates hmc every 50 s through an frpr-17 G protein-coupled receptor (GPCR) and a protein kinase A signaling cascade in hmc. hmc activation results in muscle contraction through coupling by gap junctions composed of UNC-9/Innexin. hmc activation is inhibited by the neuronal release of a second FMRFamide-like neuropeptide, FLP-9, which functions through its GPCR, frpr-21, in hmc. This study reveals a function for two opposing FMRFamide signaling pathways in controlling the rhythmic activation of a target cell through volume transmission.

Choi U et al. (2021) Proc Natl Acad Sci U S A "Presynaptic coupling by electrical synapses coordinates a rhythmic behavior by synchronizing the activities of a neuron pair."

Sieburth D, Kim S, Choi U, Hu M, Wang H

[

Proc Natl Acad Sci U S A,

2021]

Electrical synapses are specialized structures that mediate the flow of electrical currents between neurons and have well known roles in synchronizing the activities of neuronal populations, both by mediating the current transfer from more active to less active neurons and by shunting currents from active neurons to their less active neighbors. However, how these positive and negative functions of electrical synapses are coordinated to shape rhythmic synaptic outputs and behavior is not well understood. Here, using a combination of genetics, behavioral analysis, and live calcium imaging in Caenorhabditis elegans, we show that electrical synapses formed by the gap junction protein INX-1/innexin couple the presynaptic terminals of a pair of motor neurons (AVL and DVB) to synchronize their activation in response to a pacemaker signal. Live calcium imaging reveals that inx-1/innexin mutations lead to asynchronous activation of AVL and DVB, due, in part, to loss of AVL-mediated activation of DVB by the pacemaker. In addition, loss of inx-1 leads to the ectopic activation of DVB at inappropriate times during the cycle through the activation of the L-type voltage-gated calcium channel EGL-19. We propose that electrical synapses between AVL and DVB presynaptic terminals function to ensure the precise and robust execution of a specific step in a rhythmic behavior by both synchronizing the activities of presynaptic terminals in response to pacemaker signaling and by inhibiting their activation in between cycles when pacemaker signaling is low.

Choi, U. et al. (2017) International Worm Meeting "Motor neuron coupling by the presynaptic gap junction protein INX-1 ensures robustness of calcium oscillation generation during a rhythmic behavior."

Choi, U., Sieburth, D., Wang, H., Hu, M.

[

International Worm Meeting,

2017]

Rhythmic behaviors are often controlled by calcium oscillations in underlying circuits, but little is known about how these oscillations are shaped to maintain proper periodicity and to avoid arrhythmia. During the expulsion step of the C. elegans defecation motor program, calcium oscillations are generated every 50 seconds at presynaptic terminals of a pair of GABAergic motor neurons (AVL/DVB) by a peptide signal from the pacemaker (intestine), and they drive the rhythmic release of GABA and the subsequent contraction of the enteric muscles (Exp). Here we show that the gap junction protein inx-1/innexin functions to maintain the robust execution of the Exp step by regulating the generation of both normally-timed and ectopic calcium transients at AVL/DVB presynaptic terminals. inx-1/innexin null mutants restore Exp and calcium influx through voltage gated calcium channels to mutants lacking the peptide-activated presynaptic signaling pathway. However, both Exp and calcium transients occur at random times during the cycle in these mutants, suggesting that INX-1 functions to inhibit calcium influx independently of pacemaker-mediated signaling. Cell-specific rescue experiments and localization studies reveal that INX-1 is concentrated exclusively at AVL/DVB presynaptic terminals and it functions at mature synapses to regulate calcium entry. Expression of inx-1 in both AVL and DVB simultaneously is required for INX-1 function, suggesting that inx-1 may function as a gap junction to couple the two neurons. Finally, the ectopic calcium transients seen in inx-1 mutants are blocked by egl-19/VGGC mutations, or when AVL/DVB have been hyperpolarized (cell-specific expression of egl-36(gf)/VGKC). We propose that INX-1 forms gap junctions between AVL and DVB that function to ensure the proper timing of calcium entry at GABA release sites during this rhythmic behavior.

Chamberlin HM et al. (1995) Worm Breeder's Gazette "lin-49, An Essential Gene Required For Normal F and U Cells."

Chamberlin HM, Baillie DL, Sternberg PW

[

Worm Breeder's Gazette,

1995]

lin-49, an essential gene required for normal F and U cells

Nehammer C et al. (2019) Elife "Interferon--induced miR-1 alleviates toxic protein accumulation by controlling autophagy."

Nehammer C, Handley A, Pocock R, Issazadeh-Navikas S, Gopal S, Ejlerskov P, Moreira P, Lee H, Rubinsztein DC, Ng L

[

Elife,

2019]

Appropriate regulation of autophagy is crucial for clearing toxic proteins from cells. Defective autophagy results in accumulation of toxic protein aggregates that detrimentally affect cellular function and organismal survival. Here, we report that the microRNA miR-1 regulates the autophagy pathway through conserved targeting of the orthologous Tre-2/Bub2/CDC16 (TBC) Rab GTPase-activating proteins TBC-7 and TBC1D15 in Caenorhabditis elegans and mammalian cells, respectively. Loss of miR-1 causes TBC-7/TBC1D15 overexpression, leading to a block on autophagy. Further, we found that the cytokine interferon-b (IFN-b) can induce miR-1 expression in mammalian cells, reducing TBC1D15 levels, and safeguarding against proteotoxic challenges. Therefore, this work provides a potential therapeutic strategy for protein aggregation disorders.

He S et al. (2019) Genetics "NATF (Native And Tissue-Specific Fluorescence): A Strategy for Bright, Tissue-Specific GFP Labeling of Native Proteins in Caenorhabditis elegans."

Cuentas-Condori A, Miller DM, He S

[

Genetics,

2019]

GFP labeling by genome editing can reveal the authentic location of a native protein but is frequently hampered by weak GFP signals and broad expression across a range of tissues that may obscure cell-specific localization. To overcome these problems, we engineered a Native And Tissue-specific Fluorescence (NATF) strategy which combines CRISPR/Cas-9 and split-GFP to yield bright, cell-specific protein labeling. We use CRISPR/Cas9 to insert a tandem array of seven copies of the GFP11 B-strand (gfp11x7) at the genomic locus of each target protein. The resultant gfp11x7 knock-in strain is then crossed with separate reporter lines that express the complementing split-GFP fragment (gfp1-10) in specific cell types thus affording tissue-specific labeling of the target protein at its native level. We show that NATF reveals the otherwise undetectable intracellular location of the immunoglobulin protein, OIG-1, and demarcates the receptor auxiliary protein LEV-10 at cell-specific synaptic domains in the C. elegans nervous system.

Chen J et al. (2016) Food Funct "Extracts of Tsai Tai (Brassica chinensis): enhanced antioxidant activity and anti-aging effects both in vitro and in Caenorhabditis elegans."

Chen J, He X, Xiang L, Xiang Y, Liu X, Zhou X, Huang Z, Liu Y, Zhang J

[

Food Funct,

2016]

Tsai Tai is one of the most widely consumed Brassica vegetables in Asian countries because of its good taste and its nutritional benefits. This study evaluated the antioxidant capacity and possible associated health benefits of 3 Tsai Tai (Brassica chinensis) varieties, namely, Hon Tsai Tai, Pak Choi and Choi Sum. The DPPH radical scavenging ability and reducing power assays were performed to evaluate the in vitro activities of the extracts. Caenorhabditis elegans was used as an in vivo model for evaluation of beneficial health effects, including antioxidant activity and delayed aging. In vitro, the Hon Tsai Tai extract exhibited higher antioxidant activities than Pak Choi and Choi Sum, and the total phenolic contents were significantly correlated with the DPPH and RP values. In vivo, the three assayed Tsai Tai extracts significantly increased resistance against paraquat-induced oxidative stress with an increase in survival rates from 15% to 28% compared with controls. However, only the extract from Hon Tsai Tai significantly prolonged the lifespan of Caenorhabditis elegans, with an 8% increase in the mean lifespan with respect to controls. Further evidence of antioxidant protection was obtained by assessing ROS production via the DCF assay. The analyses of intracellular SOD activity and MDA content confirmed the existence of an antioxidant protective effect. These results suggest that Tsai Tai might serve as a good source of natural antioxidants, and in particular, Hon Tsai Tai could be explored as a potential dietary supplement to retard aging.

Gorelick S et al. (2019) Elife "PIE-scope, integrated cryo-correlative light and FIB/SEM microscopy."

de Marco A, Gervinskas G, Johnson TK, Handley A, Caggiano MP, Buckley G, Pocock R, Gorelick S, Whisstock JC

[

Elife,

2019]

Cryo-Electron Tomography (cryo-ET) is emerging as a revolutionary method for resolving the structure of macromolecular complexes in situ. However, sample preparation for in situ Cryo-ET is labour-intensive and can require both cryo-lamella preparation through cryo-Focused Ion Beam (FIB) milling and correlative light microscopy to ensure that the event of interest is present in the lamella. Here, we present an integrated cryo-FIB and light microscope setup called the Photon Ion Electron microscope (PIE-scope) that enables direct and rapid isolation of cellular regions containing protein complexes of interest. Specifically, we demonstrate the versatility of PIE-scope by preparing targeted cryo-lamellae from subcellular compartments of neurons from transgenic Caenorhabditis elegans and Drosophila melanogaster expressing fluorescent proteins. We designed PIE-scope to enable retrofitting of existing microscopes, which will increase the throughput and accuracy on projects requiring correlative microscopy to target protein complexes. This new approach will make cryo-correlative workflow safer and more accessible.

Nithianantham S et al. (2018) J Biol Chem "Structural basis for disassembly of katanin heterododecamers."

Al-Bassam J, McNally FJ, Nithianantham S

[

J Biol Chem,

2018]

The reorganization of microtubules in mitosis, meiosis, and development requires the microtubule-severing activity of katanin. Katanin is a heterodimer composed of an ATPase associated with diverse cellular activities (AAA) subunit and a regulatory subunit. Microtubule severing requires ATP hydrolysis by katanin's conserved AAA ATPase domains. Whereas other AAA ATPases form stable hexamers, we show that katanin forms only a monomer or dimers of heterodimers in solution. Katanin oligomers consistent with hexamers of heterodimers or heterododecamers were only observed for an ATP hydrolysis-deficient mutant in the presence of ATP. X-ray structures of katanin's AAA ATPase in monomeric nucleotide-free and pseudo-oligomeric ADP-bound states revealed conformational changes in the AAA subdomains that explained the structural basis for the instability of the katanin heterododecamer. We propose that the rapid dissociation of katanin AAA oligomers may lead to an autoinhibited state that prevents inappropriate microtubule severing or that cyclical disassembly into heterodimers may critically contribute to the microtubule-severing mechanism.

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