scholarly journals Tau, XMAP215/Msps and Eb1 jointly regulate microtubule polymerisation and bundle formation in axons

2020 ◽  
Author(s):  
Ines Hahn ◽  
Andre Voelzmann ◽  
Jill Parkin ◽  
Judith Fuelle ◽  
Paula G Slater ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Functional Unit ◽  
Axon Growth ◽  
Loss Of Function ◽  
Cellular Processes ◽  
Axon Development ◽  
Key Players ◽  
Summary Statement ◽  
High Age ◽  
Mutant Phenotypes

AbstractAxons are the enormously long cable-like cellular processes of neurons that wire nervous systems and have to survive for up to a century in humans. We lose ~40% of axons towards high age and far more in neurodegenerative diseases. Sustaining axons requires axonal transport and dynamic morphogenetic changes, both crucially dependent on bundles of microtubules that run all along axons. How polymerisation is regulated to form, repair and replace microtubules in these bundles during axon development and maintenance is virtually unknown. Here, we show in axons of Drosophila and Xenopus neurons alike that Eb1, XMAP215/Msps and Tau are key players which operate as one functional unit to promote microtubule polymerisation. Eb1 and XMAP215/Msps are interdependent core factors at the microtubule tip, whereas Tau outcompetes Eb1 binding at microtubule lattices, thus preventing its pool depletion at polymerising plus ends. In agreement with their closely interwoven functions, the three factors show the same combination of axonal loss-of-function mutant phenotypes including: (1) reduced microtubule polymerisation dynamics and shorter axon growth, indicating their importance for upholding microtubule mass in axons; (2) prominent deterioration of parallel microtubule bundles into disorganised curled conformations, indicating their key roles in promoting essential axonal architecture. We show the latter to occur through Eb1- and spectraplakin-dependent guidance of extending microtubules. We conclude that Eb1, XMAP215/Msps and Tau jointly promote microtubule polymerisation, important to regulate the quantity and bundled organisation of microtubules and offering new ways to think about developmental and degenerative axon pathologies and how to treat them.Summary statementEb1, XMAP215 and tau operate as a functional unit in axons to promote the polymerisation of microtubules and their organisation into the parallel bundles essential for axonal transport.

scholarly journals Usp14 is required for spermatogenesis and ubiquitin stress responses in Drosophila melanogaster

2019 ◽  
Author(s):  
Levente Kovács ◽  
Ágota Nagy ◽  
Margit Pál ◽  
Peter Deák
Keyword(s):  
Male Sterility ◽  
Stress Responses ◽  
Expression Patterns ◽  
Loss Of Function ◽  
Wild Type ◽  
Cellular Processes ◽  
Protein Conjugates ◽  
Covalently Linked ◽  
Mutant Phenotypes

ABSTRACTDeubiquitinating (DUB) enzymes free covalently linked ubiquitins from ubiquitin-ubiquitin and ubiquitin-protein conjugates, and thereby maintain the equilibrium between free and conjugated ubiquitins and regulate ubiquitin-mediated cellular processes. The present genetic analyses of mutant phenotypes demonstrate that loss of Usp14 function results in male sterility, with defects in spermatid individualization and reduced testicular free monoubiquitin levels. These phenotypes were rescued by germline specific overexpression of wild type Usp14. Synergistic genetic interactions with Ubi-p63E and cycloheximide sensitivity suggest that ubiquitin shortage is a primary cause of male sterility. In addition, Usp14 is predominantly expressed in testes in Drosophila, and differential expression patterns may be causative of testis-specific loss of function Usp14 phenotypes. Collectively, these results suggest a major role of Usp14 in maintaining normal steady state free monoubiquitin levels during the later stages of Drosophila spermatogenesis.

scholarly journals Tau, XMAP215/Msps and Eb1 co-operate interdependently to regulate microtubule polymerisation and bundle formation in axons

PLoS Genetics ◽  
2021 ◽  
Vol 17 (7) ◽  
pp. e1009647
Author(s):  
Ines Hahn ◽  
Andre Voelzmann ◽  
Jill Parkin ◽  
Judith B. Fülle ◽  
Paula G. Slater ◽  
...  
Keyword(s):  
Axon Growth ◽  
Axon Development ◽  
Conceptual Explanations ◽  
Mutant Phenotypes ◽  
In Cells

The formation and maintenance of microtubules requires their polymerisation, but little is known about how this polymerisation is regulated in cells. Focussing on the essential microtubule bundles in axons of Drosophila and Xenopus neurons, we show that the plus-end scaffold Eb1, the polymerase XMAP215/Msps and the lattice-binder Tau co-operate interdependently to promote microtubule polymerisation and bundle organisation during axon development and maintenance. Eb1 and XMAP215/Msps promote each other’s localisation at polymerising microtubule plus-ends. Tau outcompetes Eb1-binding along microtubule lattices, thus preventing depletion of Eb1 tip pools. The three factors genetically interact and show shared mutant phenotypes: reductions in axon growth, comet sizes, comet numbers and comet velocities, as well as prominent deterioration of parallel microtubule bundles into disorganised curled conformations. This microtubule curling is caused by Eb1 plus-end depletion which impairs spectraplakin-mediated guidance of extending microtubules into parallel bundles. Our demonstration that Eb1, XMAP215/Msps and Tau co-operate during the regulation of microtubule polymerisation and bundle organisation, offers new conceptual explanations for developmental and degenerative axon pathologies.

scholarly journals Apolipoprotein L9 interacts with LC3/GABARAP and is a microtubule-associated protein with a widespread subcellular distribution

2019 ◽  
Author(s):  
Arvind A. Thekkinghat ◽  
Kamlesh K. Yadav ◽  
Pundi N. Rangarajan
Keyword(s):  
Animal Cell ◽  
Binding Protein ◽  
Lipid Binding ◽  
Lipid Transport ◽  
Bafilomycin A1 ◽  
Transmembrane Region ◽  
Intracellular Lipid ◽  
Cellular Processes ◽  
Key Players ◽  
Summary Statement

AbstractMouse Apolipoprotein L9 is a 34-kDa phosphatidylethanolamine (PE)-binding protein. The gene is present only in mouse and rat genomes; hence it is taxonomically restricted. To understand why, it is essential to uncover details about its functions in cellular processes. Here we show that ApoL9 interacts with the proteins of the LC3 and GABARAP subfamilies, which are key players in macroautophagy. In amino-acid starved cells it preferentially interacts with lipidated LC3B, likely by binding to its PE moiety. On treatment with autophagy inhibitors bafilomycin A1 and chloroquine, ApoL9 is found near swollen mitochondria and on lysosomes/LAMP1-positive compartments. However, ApoL9 itself does not seem to be degraded as a result of autophagy, suggesting that it is not an autophagy cargo receptor. Deletions in a putative transmembrane region between amino acids 110 and 145 abolish PE-binding. In addition, ApoL9 can redistribute to stress granules, can homooligomerize, and is a microtubule-associated protein. In short, its distribution in the cell is quite widespread, suggesting that it could have functions at the intersection of membrane binding and reorganization, autophagy, cellular stress and intracellular lipid transport.Summary statementThis article is about how Apolipoprotein L9, a lipid-binding protein, has versatile properties and influences a variety of processes taking place inside an animal cell.

E3 ubiquitin ligases

2005 ◽  
Vol 41 ◽  
pp. 15-30 ◽  
Author(s):  
Helen C. Ardley ◽  
Philip A. Robinson
Keyword(s):  
Protein Complexes ◽  
Loss Of Function ◽  
Direct Role ◽  
Cellular Processes ◽  
Substrate Protein ◽  
Protein Ubiquitination ◽  
C Terminus ◽  
Full Complement ◽  
Spatio Temporal ◽  
Eukaryotic Organisms

The selectivity of the ubiquitin–26 S proteasome system (UPS) for a particular substrate protein relies on the interaction between a ubiquitin-conjugating enzyme (E2, of which a cell contains relatively few) and a ubiquitin–protein ligase (E3, of which there are possibly hundreds). Post-translational modifications of the protein substrate, such as phosphorylation or hydroxylation, are often required prior to its selection. In this way, the precise spatio-temporal targeting and degradation of a given substrate can be achieved. The E3s are a large, diverse group of proteins, characterized by one of several defining motifs. These include a HECT (homologous to E6-associated protein C-terminus), RING (really interesting new gene) or U-box (a modified RING motif without the full complement of Zn2+-binding ligands) domain. Whereas HECT E3s have a direct role in catalysis during ubiquitination, RING and U-box E3s facilitate protein ubiquitination. These latter two E3 types act as adaptor-like molecules. They bring an E2 and a substrate into sufficiently close proximity to promote the substrate's ubiquitination. Although many RING-type E3s, such as MDM2 (murine double minute clone 2 oncoprotein) and c-Cbl, can apparently act alone, others are found as components of much larger multi-protein complexes, such as the anaphase-promoting complex. Taken together, these multifaceted properties and interactions enable E3s to provide a powerful, and specific, mechanism for protein clearance within all cells of eukaryotic organisms. The importance of E3s is highlighted by the number of normal cellular processes they regulate, and the number of diseases associated with their loss of function or inappropriate targeting.

Implications of Fibroblast Growth Factors (FGFs) in Cancer: From Prognostic to Therapeutic Applications

2019 ◽  
Vol 20 (8) ◽  
pp. 852-870
Author(s):  
Hassan Dianat-Moghadam ◽  
Ladan Teimoori-Toolabi
Keyword(s):  
Growth Factors ◽  
Wound Repair ◽  
Fibroblast Growth Factors ◽  
Predictive Biomarkers ◽  
Fibroblast Growth ◽  
Loss Of Function ◽  
Cellular Processes ◽  
Fgfr Signaling ◽  
Proliferation And Metastasis ◽  
Immense Potential

Fibroblast growth factors (FGFs) are pleiotropic molecules exerting autocrine, intracrine and paracrine functions via activating four tyrosine kinase FGF receptors (FGFR), which further trigger a variety of cellular processes including angiogenesis, evasion from apoptosis, bone formation, embryogenesis, wound repair and homeostasis. Four major mechanisms including angiogenesis, inflammation, cell proliferation, and metastasis are active in FGF/FGFR-driven tumors. Furthermore, gain-of-function or loss-of-function in FGFRs1-4 which is due to amplification, fusions, mutations, and changes in tumor–stromal cells interactions, is associated with the development and progression of cancer. Although, the developed small molecule or antibodies targeting FGFR signaling offer immense potential for cancer therapy, emergence of drug resistance, activation of compensatory pathways and systemic toxicity of modulators are bottlenecks in clinical application of anti-FGFRs. In this review, we present FGF/FGFR structure and the mechanisms of its function, as well as cross-talks with other nodes and/or signaling pathways. We describe deregulation of FGF/FGFR-related mechanisms in human disease and tumor progression leading to the presentation of emerging therapeutic approaches, resistance to FGFR targeting, and clinical potentials of individual FGF family in several human cancers. Additionally, the underlying biological mechanisms of FGF/FGFR signaling, besides several attempts to develop predictive biomarkers and combination therapies for different cancers have been explored.

scholarly journals The Putative Eukaryote-LikeO-GlcNAc Transferase of the Cyanobacterium Synechococcus elongatus PCC 7942 Hydrolyzes UDP-GlcNAc and Is Involved in Multiple Cellular Processes

2014 ◽  
Vol 197 (2) ◽  
pp. 354-361 ◽  
Author(s):  
Kerry A. Sokol ◽  
Neil E. Olszewski
Keyword(s):  
Deletion Mutant ◽  
Bacterial Species ◽  
Synechococcus Elongatus ◽  
Single Amino Acid ◽  
Content Type ◽  
Cellular Processes ◽  
Mutant Phenotypes ◽  
Glcnac Transferase ◽  
Pcc 7942 ◽  
Mutant Cells

The posttranslational addition of a single O-linked β-N-acetylglucosamine (O-GlcNAc) to serine or threonine residues regulates numerous metazoan cellular processes. The enzyme responsible for this modification,O-GlcNAc transferase (OGT), is conserved among a wide variety of organisms and is critical for the viability of many eukaryotes. Although OGTs with domain structures similar to those of eukaryotic OGTs are predicted for many bacterial species, the cellular roles of these OGTs are unknown. We have identified a putative OGT in the cyanobacteriumSynechococcus elongatusPCC 7942 that shows active-site homology and similar domain structure to eukaryotic OGTs. An OGT deletion mutant was created and found to exhibit several phenotypes. Without agitation, mutant cells aggregate and settle out of the medium. The mutant cells have higher free inorganic phosphate levels, wider thylakoid lumen, and differential accumulation of electron-dense inclusion bodies. These phenotypes are rescued by reintroduction of the wild-type OGT but are not fully rescued by OGTs with single amino acid substitutions corresponding to mutations that reduce eukaryotic OGT activity.S. elongatusOGT purified fromEscherichia colihydrolyzed the sugar donor, UDP-GlcNAc, while the mutant OGTs that did not fully rescue the deletion mutant phenotypes had reduced or no activity. These results suggest that bacterial eukaryote-like OGTs, like their eukaryotic counterparts, influence multiple processes.

scholarly journals Goα Regulates Volatile Anesthetic Action in Caenorhabditis elegans

Genetics ◽  
2001 ◽  
Vol 158 (2) ◽  
pp. 643-655 ◽  
Author(s):  
Bruno van Swinderen ◽  
Laura B Metz ◽  
Laynie D Shebester ◽  
Jane E Mendel ◽  
Paul W Sternberg ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Novel Mutation ◽  
Volatile Anesthetic ◽  
Loss Of Function ◽  
Wild Type ◽  
Α Subunit ◽  
C Elegans ◽  
Missense Mutant ◽  
Anesthetic Action ◽  
Mutant Phenotypes

Abstract To identify genes controlling volatile anesthetic (VA) action, we have screened through existing Caenorhabditis elegans mutants and found that strains with a reduction in Go signaling are VA resistant. Loss-of-function mutants of the gene goa-1, which codes for the α-subunit of Go, have EC50s for the VA isoflurane of 1.7- to 2.4-fold that of wild type. Strains overexpressing egl-10, which codes for an RGS protein negatively regulating goa-1, are also isoflurane resistant. However, sensitivity to halothane, a structurally distinct VA, is differentially affected by Go pathway mutants. The RGS overexpressing strains, a goa-1 missense mutant found to carry a novel mutation near the GTP-binding domain, and eat-16(rf) mutants, which suppress goa-1(gf) mutations, are all halothane resistant; goa-1(null) mutants have wild-type sensitivities. Double mutant strains carrying mutations in both goa-1 and unc-64, which codes for a neuronal syntaxin previously found to regulate VA sensitivity, show that the syntaxin mutant phenotypes depend in part on goa-1 expression. Pharmacological assays using the cholinesterase inhibitor aldicarb suggest that VAs and GOA-1 similarly downregulate cholinergic neurotransmitter release in C. elegans. Thus, the mechanism of action of VAs in C. elegans is regulated by Goα, and presynaptic Goα-effectors are candidate VA molecular targets.

scholarly journals A library of MiMICs allows tagging of genes and reversible, spatial and temporal knockdown of proteins in Drosophila

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Sonal Nagarkar-Jaiswal ◽  
Pei-Tseng Lee ◽  
Megan E Campbell ◽  
Kuchuan Chen ◽  
Stephanie Anguiano-Zarate ◽  
...  
Keyword(s):  
Null Mutant ◽  
Loss Of Function ◽  
Severe Loss ◽  
New Strategy ◽  
Mutant Phenotypes

Here, we document a collection of ∼7434 MiMIC (Minos Mediated Integration Cassette) insertions of which 2854 are inserted in coding introns. They allowed us to create a library of 400 GFP-tagged genes. We show that 72% of internally tagged proteins are functional, and that more than 90% can be imaged in unfixed tissues. Moreover, the tagged mRNAs can be knocked down by RNAi against GFP (iGFPi), and the tagged proteins can be efficiently knocked down by deGradFP technology. The phenotypes associated with RNA and protein knockdown typically correspond to severe loss of function or null mutant phenotypes. Finally, we demonstrate reversible, spatial, and temporal knockdown of tagged proteins in larvae and adult flies. This new strategy and collection of strains allows unprecedented in vivo manipulations in flies for many genes. These strategies will likely extend to vertebrates.

scholarly journals MiRNA-143 mediates the proliferative signaling pathway of FSH and regulates estradiol production

2017 ◽  
Vol 234 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Li Zhang ◽  
XiaoXin Zhang ◽  
Xuejing Zhang ◽  
Yu Lu ◽  
Lei Li ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Granulosa Cell ◽  
Granulosa Cells ◽  
Loss Of Function ◽  
Cellular Processes ◽  
Cell Functions ◽  
Genes Expression ◽  
Underlying Mechanisms

MicroRNAs (MiRNAs) play important regulatory roles in many cellular processes. MiR-143 is highly enriched in the mouse ovary, but its roles and underlying mechanisms are not well understood. In the current study, we show that miR-143 is located in granulosa cells of primary, secondary and antral follicles. To explore the specific functions of miR-143, we transfected miR-143 inhibitor into primary cultured granulosa cells to study the loss of function of miR-143 and the results showed that miR-143 silencing significantly increased estradiol production and steroidogenesis-related gene expression. Moreover, our in vivo and in vitro studies showed that follicular stimulating hormone (FSH) significantly decreased miR-143 expression. This function of miR-143 is accomplished by its binding to the 3’-UTR of KRAS mRNA. Furthermore, our results demonstrated that miR-143 acts as a negative regulating molecule mediating the signaling pathway of FSH and affecting estradiol production by targeting KRAS. MiR-143 also negatively acts in regulating granulosa cells proliferation and cell cycle-related genes expression. These findings indicate that miR-143 plays vital roles in FSH-induced estradiol production and granulosa cell proliferation, providing a novel mechanism that involves miRNA in regulating granulosa cell functions.

Sensory activity affects sensory axon development in C. elegans

Development ◽  
1999 ◽  
Vol 126 (9) ◽  
pp. 1891-1902 ◽  
Author(s):  
E.L. Peckol ◽  
J.A. Zallen ◽  
J.C. Yarrow ◽  
C.I. Bargmann
Keyword(s):  
Nervous System ◽  
Molecular Mechanisms ◽  
Sensory Deprivation ◽  
Axon Growth ◽  
System Structure ◽  
Sensory Axon ◽  
C Elegans ◽  
Sensory Axons ◽  
Axon Development ◽  
Sensory Activity

The simple nervous system of the nematode C. elegans consists of 302 neurons with highly reproducible morphologies, suggesting a hard-wired program of axon guidance. Surprisingly, we show here that sensory activity shapes sensory axon morphology in C. elegans. A class of mutants with deformed sensory cilia at their dendrite endings have extra axon branches, suggesting that sensory deprivation disrupts axon outgrowth. Mutations that alter calcium channels or membrane potential cause similar defects. Cell-specific perturbations of sensory activity can cause cell-autonomous changes in axon morphology. Although the sensory axons initially reach their targets in the embryo, the mutations that alter sensory activity cause extra axon growth late in development. Thus, perturbations of activity affect the maintenance of sensory axon morphology after an initial pattern of innervation is established. This system provides a genetically tractable model for identifying molecular mechanisms linking neuronal activity to nervous system structure.

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