scholarly journals The Caenorhabditis elegans microtubule minus-end binding homolog PTRN-1 stabilizes synapses and neurites

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Jana Dorfman Marcette ◽  
Jessica Jie Chen ◽  
Michael L Nonet
Keyword(s):  
Neurite Growth ◽  
Wild Type ◽  
C Elegans ◽  
Microtubule Stabilization ◽  
Neuronal Remodeling ◽  
Morphological Defects ◽  
Map Kinase Pathway ◽  
The Stability ◽  
Kinase Pathway

Microtubule dynamics facilitate neurite growth and establish morphology, but the role of minus-end binding proteins in these processes is largely unexplored. CAMSAP homologs associate with microtubule minus-ends, and are important for the stability of epithelial cell adhesions. In this study, we report morphological defects in neurons and neuromuscular defects in mutants of the C. elegans CAMSAP, ptrn-1. Mechanosensory neurons initially extend wild-type neurites, and subsequently remodel by overextending neurites and retracting synaptic branches and presynaptic varicosities. This neuronal remodeling can be activated by mutations known to alter microtubules, and depends on a functioning DLK-1 MAP kinase pathway. We found that PTRN-1 localizes to both neurites and synapses, and our results suggest that alterations of microtubule structures caused by loss of PTRN-1 function activates a remodeling program leading to changes in neurite morphology. We propose a model whereby minus-end microtubule stabilization mediated by a functional PTRN-1 is necessary for morphological maintenance of neurons.

scholarly journals Role of Vif in Stability of the Human Immunodeficiency Virus Type 1 Core

2000 ◽  
Vol 74 (23) ◽  
pp. 11055-11066 ◽  
Author(s):  
Åsa Öhagen ◽  
Dana Gabuzda
Keyword(s):  
Human Immunodeficiency Virus ◽  
Dna Synthesis ◽  
Virus Entry ◽  
Wild Type ◽  
The Core ◽  
Immunodeficiency Virus ◽  
The Stability ◽  
Hiv 1

ABSTRACT The Vif protein of human immunodeficiency virus type 1 (HIV-1) is important for virion infectivity. Previous studies have shown thatvif-defective virions exhibit structural abnormalities in the virus core and are defective in the ability to complete proviral DNA synthesis in acutely infected cells. We developed novel assays to assess the relative stability of the core in HIV-1 virions. Using these assays, we examined the role of Vif in the stability of the HIV-1 core. The integrity of the core was examined following virion permeabilization or removal of the lipid envelope and treatment with various triggers, including S100 cytosol, deoxynucleoside triphosphates, detergents, NaCl, and buffers of different pH to mimic aspects of the uncoating and disassembly process which occurs after virus entry but preceding or during reverse transcription.vif mutant cores were more sensitive to disruption by all triggers tested than wild-type cores, as determined by endogenous reverse transcriptase (RT) assays, biochemical analyses, and electron microscopy. RT and the p7 nucleocapsid protein were released more readily from vif mutant virions than from wild-type virions, suggesting that the internal nucleocapsid is less stably packaged in the absence of Vif. Purified cores could be isolated from wild-type but not vif mutant virions by sedimentation through detergent-treated gradients. These results demonstrate that Vif increases the stability of virion cores. This may permit efficient viral DNA synthesis by preventing premature degradation or disassembly of viral nucleoprotein complexes during early events after virus entry.

scholarly journals The role of an evolutionarily conserved cis-proline in the thioredoxin-like domain of human class Alpha glutathione transferase A1-1

2003 ◽  
Vol 372 (1) ◽  
pp. 241-246 ◽  
Author(s):  
Chris NATHANIEL ◽  
Louise A. WALLACE ◽  
Jonathan BURKE ◽  
Heini W. DIRR
Keyword(s):  
Glutathione Transferase ◽  
Conformational Stability ◽  
Wild Type ◽  
Catalytic Function ◽  
Evolutionarily Conserved ◽  
Glutathione S Transferases ◽  
Equilibrium Unfolding ◽  
The Stability ◽  
Unfolding Kinetics

The thioredoxin-like fold has a βαβαββα topology, and most proteins/domains with this fold have a topologically conserved cis-proline residue at the N-terminus of β-strand 3. This residue plays an important role in the catalytic function and stability of thioredoxin-like proteins, but is reported not to contribute towards the stability of glutathione S-transferases (GSTs) [Allocati, Casalone, Masulli, Caccarelli, Carletti, Parker and Di Ilio (1999) FEBS Lett. 445, 347–350]. In order to further address the role of the cis-proline in the structure, function and stability of GSTs, cis-Pro-56 in human GST (hGST) A1-1 was replaced with a glycine, and the properties of the P56G mutant were compared with those of the wild-type protein. Not only was the catalytic function of the mutant dramatically reduced, so was its conformational stability, as indicated by equilibrium unfolding and unfolding kinetics experiments with urea as denaturant. These findings are discussed in the context of other thioredoxin-like proteins.

scholarly journals Extracellular Zinc Triggers ERK-dependent Activation of Na+/H+Exchange in Colonocytes Mediated by the Zinc-sensing Receptor

2004 ◽  
Vol 279 (50) ◽  
pp. 51804-51816 ◽  
Author(s):  
Hagit Azriel-Tamir ◽  
Haleli Sharir ◽  
Betty Schwartz ◽  
Michal Hershfinkel
Keyword(s):  
Cell Proliferation ◽  
Map Kinase ◽  
Ph Homeostasis ◽  
Ht29 Cells ◽  
Intracellular Release ◽  
Map Kinase Pathway ◽  
Zinc Sensing ◽  
Multiple Signaling ◽  
Kinase Pathway

Extracellular zinc promotes cell proliferation and its deficiency leads to impairment of this process, which is particularly important in epithelial cells. We have recently characterized a zinc-sensing receptor (ZnR) linking extracellular zinc to intracellular release of calcium. In the present study, we addressed the role of extracellular zinc, acting via the ZnR, in regulating the MAP kinase pathway and Na+/H+exchange in colonocytes. We demonstrate that Ca2+release, mediated by the ZnR, induces phosphorylation of ERK1/2, which is highly metal-specific, mediated by physiological concentrations of extracellular Zn2+but not by Cd2+, Fe2+, Ni2+, or Mn2+. Desensitization of the ZnR by Zn2+, is followed by ∼90% inhibition of the Zn2+-dependent ERK1/2 phosphorylation, indicating that the ZnR is a principal link between extracellular Zn2+and ERK1/2 activation. Application of both the IP3pathway and PI 3-kinase antagonists largely inhibited Zn2+-dependent ERK1/2 phosphorylation. The physiological significance of the Zn2+-dependent activation of ERK1/2 was addressed by monitoring Na+/H+exchanger activity in HT29 cells and in native colon epithelium. Preincubation of the cells with zinc was followed by robust activation of Na+/H+exchange, which was eliminated by cariporide (0.5 μm); indicating that zinc enhances the activity of NHE1. Activation of NHE1 by zinc was totally blocked by the ERK1/2 inhibitor, U0126. Prolonged acidification, in contrast, stimulates NHE1 by a distinct pathway that is not affected by extracellular Zn2+or inhibitors of the MAP kinase pathway. Desensitization of ZnR activity eliminates the Zn2+-dependent, but not the prolonged acidification-dependent activation of NHE1, indicating that Zn2+-dependent activation of H+extrusion is specifically mediated by the ZnR. Our results support a role for extracellular zinc, acting through the ZnR, in regulating multiple signaling pathways that affect pH homeostasis in colonocytes. Furthermore activation of both, ERK and NHE1, by extracellular zinc may provide the mechanism linking zinc to enhanced cell proliferation.

scholarly journals Role of the Sec22b–E-Syt complex in neurite growth and ramification

2020 ◽  
Vol 133 (18) ◽  
pp. jcs247148 ◽  
Author(s):  
Alessandra Gallo ◽  
Lydia Danglot ◽  
Francesca Giordano ◽  
Bailey Hewlett ◽  
Thomas Binz ◽  
...  
Keyword(s):  
Nervous System ◽  
Opposite Effect ◽  
Neurite Growth ◽  
Lipid Transfer ◽  
Wild Type ◽  
Lipid Transfer Proteins ◽  
Contact Sites ◽  
Developing Neurons ◽  
Clostridial Neurotoxin

ABSTRACTAxons and dendrites are long and often ramified neurites that need particularly intense plasma membrane (PM) expansion during the development of the nervous system. Neurite growth depends on non-fusogenic Sec22b–Stx1 SNARE complexes at endoplasmic reticulum (ER)–PM contacts. Here, we show that Sec22b interacts with members of the extended synaptotagmin (E-Syt) family of ER lipid transfer proteins (LTPs), and this interaction depends on the longin domain of Sec22b. Overexpression of E-Syts stabilizes Sec22b–Stx1 association, whereas silencing of E-Syts has the opposite effect. Overexpression of wild-type E-Syt2, but not mutants unable to transfer lipids or attach to the ER, increase the formation of axonal filopodia and ramification of neurites in developing neurons. This effect is inhibited by a clostridial neurotoxin cleaving Stx1, and expression of the Sec22b longin domain and a Sec22b mutant with an extended linker between the SNARE and transmembrane domains. We conclude that Sec22b–Stx1 ER–PM contact sites contribute to PM expansion by interacting with LTPs, such as E-Syts.This article has an associated First Person interview with the first author of the paper.

scholarly journals Rapid capping in alpha-spectrin-deficient MEL cells from mice afflicted with hereditary hemolytic anemia.

1994 ◽  
Vol 125 (5) ◽  
pp. 1057-1065 ◽  
Author(s):  
S C Dahl ◽  
R W Geib ◽  
M T Fox ◽  
M Edidin ◽  
D Branton
Keyword(s):  
Membrane Structure ◽  
Membrane Skeleton ◽  
Wild Type ◽  
Membrane Glycoproteins ◽  
Erythroleukemia Cells ◽  
Alpha Spectrin ◽  
Erythroleukemia Cell ◽  
The Stability ◽  
In Cells

A spectrin-based membrane skeleton is important for the stability and organization of the erythrocyte. To study the role of spectrin in cells that possess complex cytoskeletons, we have generated alpha-spectrin-deficient erythroleukemia cell lines from sph/sph mice. These cells contain beta-spectrin, but lack alpha-spectrin as determined by immunoblot and Northern blot analyses. The effects of alpha-spectrin deficiency are apparent in the cells' irregular shape and fragility in culture. Capping of membrane glycoproteins by fluorescent lectin or antibodies occurs more rapidly in sph/sph than in wild-type erythroleukemia cells, and the caps appear more concentrated. The data support the idea that spectrin plays an important role in organizing membrane structure and limiting the lateral mobility of integral membrane glycoproteins in cells other than mature erythrocytes.

Axonal cell-adhesion molecule L1 in CNS myelination

2004 ◽  
Vol 1 (1) ◽  
pp. 65-72 ◽  
Author(s):  
G. BARBIN ◽  
M.S. AIGROT ◽  
P. CHARLES ◽  
A. FOUCHER ◽  
M. GRUMET ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecule ◽  
Cell Adhesion Molecule ◽  
Culture Medium ◽  
Immunoglobulin Superfamily ◽  
Map Kinase Pathway ◽  
Cell Adhesion Molecule L1 ◽  
Cns Myelination ◽  
Kinase Pathway

Of the axonal signals influencing myelination, adhesion molecules expressed at the axonal surface are strong candidates to mediate interactions between myelinating cells and axons. The recognition cell-adhesion molecule L1, a member of the immunoglobulin superfamily has been shown to play important roles in neuronal migration and survival, and in PNS myelination. We have investigated the role of axonally expressed L1 in CNS myelination. In co-cultures of myelinating oligodendrocytes and neurons derived from murine brain, we demonstrate that, before myelination, L1 immunoreactivity is confined to neurites. After myelination commences, L1 expression is downregulated on myelinated axons and adjacent, but not yet myelinated, internodes. Interfering with L1 before the onset of myelination, by adding either anti-L1 antibody or L1-Fc fusion proteins to the culture medium, inhibits myelination. In addition, in purified cultures of oligodendrocytes, L1-Fc fusion protein prevents lysophosphatidic acid-induced activation of the mitogen-activated kinase (MAP)-kinase pathway. Together, our data indicate that L1 is involved in the initiation of CNS myelination, and that this effect might involve the dephosphorylation of oligodendroglial phosphoproteins.

scholarly journals Aurora-A kinase is required for centrosome maturation in Caenorhabditis elegans

2001 ◽  
Vol 155 (7) ◽  
pp. 1109-1116 ◽  
Author(s):  
Eva Hannak ◽  
Matthew Kirkham ◽  
Anthony A. Hyman ◽  
Karen Oegema
Keyword(s):  
Caenorhabditis Elegans ◽  
Fluorescence Intensity ◽  
Maturation Process ◽  
Aurora A Kinase ◽  
Aurora A ◽  
Wild Type ◽  
C Elegans ◽  
Nuclear Envelope Breakdown ◽  
Pericentriolar Material

Centrosomes mature as cells enter mitosis, accumulating γ-tubulin and other pericentriolar material (PCM) components. This occurs concomitant with an increase in the number of centrosomally organized microtubules (MTs). Here, we use RNA-mediated interference (RNAi) to examine the role of the aurora-A kinase, AIR-1, during centrosome maturation in Caenorhabditis elegans. In air-1(RNAi) embryos, centrosomes separate normally, an event that occurs before maturation in C. elegans. After nuclear envelope breakdown, the separated centrosomes collapse together, and spindle assembly fails. In mitotic air-1(RNAi) embryos, centrosomal α-tubulin fluorescence intensity accumulates to only 40% of wild-type levels, suggesting a defect in the maturation process. Consistent with this hypothesis, we find that AIR-1 is required for the increase in centrosomal γ-tubulin and two other PCM components, ZYG-9 and CeGrip, as embryos enter mitosis. Furthermore, the AIR-1–dependent increase in centrosomal γ-tubulin does not require MTs. These results suggest that aurora-A kinases are required to execute a MT-independent pathway for the recruitment of PCM during centrosome maturation.

scholarly journals Inhibition underlies fast undulatory locomotion in C. elegans

2020 ◽  
Author(s):  
Lan Deng ◽  
Jack Denham ◽  
Charu Arya ◽  
Omer Yuval ◽  
Netta Cohen ◽  
...  
Keyword(s):  
Computational Models ◽  
Body Wall ◽  
Activity Patterns ◽  
Wild Type ◽  
C Elegans ◽  
Body Wall Muscles ◽  
Undulatory Locomotion ◽  
Gaba Transmission ◽  
Cross Inhibition

AbstractInhibition plays important roles in modulating the neural activities of sensory and motor systems at different levels from synapses to brain regions. To achieve coordinated movement, motor systems produce alternating contraction of antagonist muscles, whether along the body axis or within and among limbs. In the nematode C. elegans, a small network involving excitatory cholinergic and inhibitory GABAergic motoneurons generates the dorsoventral alternation of body-wall muscles that supports undulatory locomotion. Inhibition has been suggested to be necessary for backward undulation because mutants that are defective in GABA transmission exhibit a shrinking phenotype in response to a harsh touch to the head, whereas wild-type animals produce a backward escape response. Here, we demonstrate that the shrinking phenotype is exhibited by wild-type as well as mutant animals in response to harsh touch to the head or tail, but only GABA transmission mutants show slow locomotion after stimulation. Impairment of GABA transmission, either genetically or optogenetically, induces lower undulation frequency and lower translocation speed during crawling and swimming in both directions. The activity patterns of GABAergic motoneurons are different during low and high undulation frequencies. During low undulation frequency, GABAergic VD and DD motoneurons show similar activity patterns, while during high undulation frequency, their activity alternates. The experimental results suggest at least three non-mutually exclusive roles for inhibition that could underlie fast undulatory locomotion in C. elegans, which we tested with computational models: cross-inhibition or disinhibition of body-wall muscles, or inhibitory reset.Significance StatementInhibition serves multiple roles in the generation, maintenance, and modulation of the locomotive program and supports the alternating activation of antagonistic muscles. When the locomotor frequency increases, more inhibition is required. To better understand the role of inhibition in locomotion, we used C. elegans as an animal model, and challenged a prevalent hypothesis that cross-inhibition supports the dorsoventral alternation. We find that inhibition is related to the speed rather than the direction of locomotion and demonstrate that inhibition is unnecessary for muscle alternation during slow undulation in either direction but crucial to sustain rapid dorsoventral alternation. We combined calcium imaging of motoneurons and muscle with computational models to test hypotheses for the role of inhibition in locomotion.

scholarly journals The MAP kinase pathway coordinates crossover designation with disassembly of synaptonemal complex proteins during meiosis

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Saravanapriah Nadarajan ◽  
Firaz Mohideen ◽  
Yonatan B Tzur ◽  
Nuria Ferrandiz ◽  
Oliver Crawley ◽  
...  
Keyword(s):  
Map Kinase ◽  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Meiotic Chromosome ◽  
Late Pachytene ◽  
C Elegans ◽  
Map Kinase Pathway ◽  
Rho Gef ◽  
Kinase Signaling Pathway ◽  
Kinase Pathway

Asymmetric disassembly of the synaptonemal complex (SC) is crucial for proper meiotic chromosome segregation. However, the signaling mechanisms that directly regulate this process are poorly understood. Here we show that the mammalian Rho GEF homolog, ECT-2, functions through the conserved RAS/ERK MAP kinase signaling pathway in the C. elegans germline to regulate the disassembly of SC proteins. We find that SYP-2, a SC central region component, is a potential target for MPK-1-mediated phosphorylation and that constitutively phosphorylated SYP-2 impairs the disassembly of SC proteins from chromosomal domains referred to as the long arms of the bivalents. Inactivation of MAP kinase at late pachytene is critical for timely disassembly of the SC proteins from the long arms, and is dependent on the crossover (CO) promoting factors ZHP-3/RNF212/Zip3 and COSA-1/CNTD1. We propose that the conserved MAP kinase pathway coordinates CO designation with the disassembly of SC proteins to ensure accurate chromosome segregation.

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