scholarly journals A conceptual view at microtubule plus end dynamics in neuronal axons

2016 ◽  
Author(s):  
André Voelzmann ◽  
Ines Hahn ◽  
Simon P. Pearce ◽  
Natalia Sánchez-Soriano ◽  
Andreas Prokop
Keyword(s):  
Nervous System ◽  
Conceptual Understanding ◽  
Molecular Mechanisms ◽  
Protein Complexes ◽  
Building Blocks ◽  
Cellular Level ◽  
Cellular Functions ◽  
Dynamic Changes ◽  
Plastic Rearrangement

AbstractAxons are the cable-like protrusions of neurons which wire up the nervous system. Polar bundles of microtubules (MTs) constitute their structural backbones and are highways for life-sustaining transport between proximal cell bodies and distal synapses. Any morphogenetic changes of axons during development, plastic rearrangement, regeneration or degeneration depend on dynamic changes of these MT bundles. A key mechanism for implementing such changes is the coordinated polymerisation and depolymerisation at the plus ends of MTs within these bundles. To gain an understanding of how such regulation can be achieved at the cellular level, we provide here an integrated overview of the extensive knowledge we have about the molecular mechanisms regulating MT de/polymerisation. We first summarise insights gained from work in vitro, then describe the machinery which supplies the essential tubulin building blocks, the protein complexes associating with MT plus ends, and MT shaft-based mechanisms that influence plus end dynamics. We briefly summarise the contribution of MT plus end dynamics to important cellular functions in axons, and conclude by discussing the challenges and potential strategies of integrating the existing molecular knowledge into conceptual understanding at the level of axons.

scholarly journals Novel in vitro Experimental Approaches to Study Myelination and Remyelination in the Central Nervous System

2021 ◽  
Vol 15 ◽  
Author(s):  
Davide Marangon ◽  
Nicolò Caporale ◽  
Marta Boccazzi ◽  
Maria P. Abbracchio ◽  
Giuseppe Testa ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Molecular Mechanisms ◽  
Disease Modeling ◽  
Brain Physiology ◽  
Pathological Conditions ◽  
Approaches To Study ◽  
The Central Nervous System ◽  
Experimental Approaches

Myelin is the lipidic insulating structure enwrapping axons and allowing fast saltatory nerve conduction. In the central nervous system, myelin sheath is the result of the complex packaging of multilamellar extensions of oligodendrocyte (OL) membranes. Before reaching myelinating capabilities, OLs undergo a very precise program of differentiation and maturation that starts from OL precursor cells (OPCs). In the last 20 years, the biology of OPCs and their behavior under pathological conditions have been studied through several experimental models. When co-cultured with neurons, OPCs undergo terminal maturation and produce myelin tracts around axons, allowing to investigate myelination in response to exogenous stimuli in a very simple in vitro system. On the other hand, in vivo models more closely reproducing some of the features of human pathophysiology enabled to assess the consequences of demyelination and the molecular mechanisms of remyelination, and they are often used to validate the effect of pharmacological agents. However, they are very complex, and not suitable for large scale drug discovery screening. Recent advances in cell reprogramming, biophysics and bioengineering have allowed impressive improvements in the methodological approaches to study brain physiology and myelination. Rat and mouse OPCs can be replaced by human OPCs obtained by induced pluripotent stem cells (iPSCs) derived from healthy or diseased individuals, thus offering unprecedented possibilities for personalized disease modeling and treatment. OPCs and neural cells can be also artificially assembled, using 3D-printed culture chambers and biomaterial scaffolds, which allow modeling cell-to-cell interactions in a highly controlled manner. Interestingly, scaffold stiffness can be adopted to reproduce the mechanosensory properties assumed by tissues in physiological or pathological conditions. Moreover, the recent development of iPSC-derived 3D brain cultures, called organoids, has made it possible to study key aspects of embryonic brain development, such as neuronal differentiation, maturation and network formation in temporal dynamics that are inaccessible to traditional in vitro cultures. Despite the huge potential of organoids, their application to myelination studies is still in its infancy. In this review, we shall summarize the novel most relevant experimental approaches and their implications for the identification of remyelinating agents for human diseases such as multiple sclerosis.

scholarly journals Tiny Actors in the Big Cellular World: Extracellular Vesicles Playing Critical Roles in Cancer

2020 ◽  
Vol 21 (20) ◽  
pp. 7688 ◽  
Author(s):  
Ancuta Jurj ◽  
Cecilia Pop-Bica ◽  
Ondrej Slaby ◽  
Cristina D. Ştefan ◽  
William C. Cho ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Molecular Mechanisms ◽  
Recipient Cell ◽  
Cell Communication ◽  
Therapeutic Agents ◽  
Bioactive Molecules ◽  
Cellular Functions ◽  
Membrane Bound

Communications among cells can be achieved either via direct interactions or via secretion of soluble factors. The emergence of extracellular vesicles (EVs) as entities that play key roles in cell-to-cell communication offer opportunities in exploring their features for use in therapeutics; i.e., management and treatment of various pathologies, such as those used for cancer. The potential use of EVs as therapeutic agents is attributed not only for their cell membrane-bound components, but also for their cargos, mostly bioactive molecules, wherein the former regulate interactions with a recipient cell while the latter trigger cellular functions/molecular mechanisms of a recipient cell. In this article, we highlight the involvement of EVs in hallmarks of a cancer cell, particularly focusing on those molecular processes that are influenced by EV cargos. Moreover, we explored the roles of RNA species and proteins carried by EVs in eliciting drug resistance phenotypes. Interestingly, engineered EVs have been investigated and proposed as therapeutic agents in various in vivo and in vitro studies, as well as in several clinical trials.

scholarly journals Aldehyde Dehydrogenases: Not Just Markers, but Functional Regulators of Stem Cells

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Giuseppe Vassalli
Keyword(s):  
Stem Cells ◽  
Molecular Mechanisms ◽  
Cell Types ◽  
Cellular Function ◽  
Stem Cell Marker ◽  
Cell Populations ◽  
Aldh Activity ◽  
Cellular Functions ◽  
Stem And Progenitor Cells

Aldehyde dehydrogenase (ALDH) is a superfamily of enzymes that detoxify a variety of endogenous and exogenous aldehydes and are required for the biosynthesis of retinoic acid (RA) and other molecular regulators of cellular function. Over the past decade, high ALDH activity has been increasingly used as a selectable marker for normal cell populations enriched in stem and progenitor cells, as well as for cell populations from cancer tissues enriched in tumor-initiating stem-like cells. Mounting evidence suggests that ALDH not only may be used as a marker for stem cells but also may well regulate cellular functions related to self-renewal, expansion, differentiation, and resistance to drugs and radiation. ALDH exerts its functional actions partly through RA biosynthesis, as all-trans RA reverses the functional effects of pharmacological inhibition or genetic suppression of ALDH activity in many cell types in vitro. There is substantial evidence to suggest that the role of ALDH as a stem cell marker comes down to the specific isoform(s) expressed in a particular tissue. Much emphasis has been placed on the ALDH1A1 and ALDH1A3 members of the ALDH1 family of cytosolic enzymes required for RA biosynthesis. ALDH1A1 and ALDH1A3 regulate cellular function in both normal stem cells and tumor-initiating stem-like cells, promoting tumor growth and resistance to drugs and radiation. An improved understanding of the molecular mechanisms by which ALDH regulates cellular function will likely open new avenues in many fields, especially in tissue regeneration and oncology.

scholarly journals DNA polymerase iota and related Rad30–like enzymes

2001 ◽  
Vol 356 (1405) ◽  
pp. 53-60 ◽  
Author(s):  
John P. McDonald ◽  
Agnès Tissier ◽  
Ekaterina G. Frank ◽  
Shigenori Iwai ◽  
Fumio Hanaoka ◽  
...  
Keyword(s):  
Dna Polymerase ◽  
Xeroderma Pigmentosum ◽  
Molecular Mechanisms ◽  
Dna Polymerases ◽  
Cellular Functions ◽  
Translesion Dna Synthesis ◽  
Dna Polymerase Iota ◽  
Biochemical Studies ◽  
Template Dna

Until recently, the molecular mechanisms of translesion DNA synthesis (TLS), a process whereby a damaged base is used as a template for continued replication, was poorly understood. This area of scientific research has, however, been revolutionized by the finding that proteins long implicated in TLS are, in fact, DNA polymerases. Members of this so–called UmuC/DinB/Rev1/Rad30 superfamily of polymerases have been identified in prokaryotes, eukaryotes and archaea. Biochemical studies with the highly purified polymerases reveal that some, but not all, can traverse blocking lesions in template DNA. All of them share a common feature, however, in that they exhibit low fidelity when replicating undamaged DNA. Of particular interest to us is the Rad30 subfamily of polymerases found exclusively in eukaryotes. Humans possess two Rad30 paralogs, Rad30A and Rad30B. The RAD30A gene encodes DNA polymerase η and defects in the protein lead to the xeroderma pigmentosum variant (XP–V) phenotype in humans. Very recently RAD30B has also been shown to encode a novel DNA polymerase, designated as Pol ι. Based upon in vitro studies, it appears that Pol ι has the lowest fidelity of any eukaryotic polymerase studied to date and we speculate as to the possible cellular functions of such a remarkably error–prone DNA polymerase.

scholarly journals Cellular and molecular mechanisms of the demyelination in the central nervous system and cell therapy approaches

2017 ◽  
Vol 5 (1) ◽  
pp. 74-78
Author(s):  
V. Tsymbaliuk ◽  
V. Semenova ◽  
L. Pichkur ◽  
O. Velychko ◽  
D. Egorova
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Cell Therapy ◽  
Molecular Mechanisms ◽  
Molecular Genetic ◽  
Light And Electron Microscopy ◽  
Cellular Level ◽  
Molecular Features ◽  
The Central Nervous System ◽  
Demyelinating Disorders

The review summarizes the current concepts of cell-tissue and molecular features of development of demyelinating processes in the central nervous system related to multiple sclerosis and its animal model – allergic encephalomyelitis. An analysis of recently published studies of this pathology, carried out with light and electron microscopy and immunohistochemical and molecular genetic methods, is given. New methodological approaches to the study of the pathomorhological aspects of demyelinating disorders allowed receiving in-depth understanding of the etiology and mechanisms of demyelination processes in the brain and spinal cord tissues at the cellular level and identifying the ways to develop effective modern methods of pathogenetic treatment of these diseases using cell therapy.

scholarly journals VASP is a processive actin polymerase that requires monomeric actin for barbed end association

2010 ◽  
Vol 191 (3) ◽  
pp. 571-584 ◽  
Author(s):  
Scott D. Hansen ◽  
R. Dyche Mullins
Keyword(s):  
Ionic Strength ◽  
Total Internal Reflection ◽  
Molecular Mechanisms ◽  
Binding Modes ◽  
Cellular Functions ◽  
Actin Networks ◽  
Filament Assembly ◽  
Binding Event ◽  
Low Ionic Strength

Ena/VASP proteins regulate the actin cytoskeleton during cell migration and morphogenesis and promote assembly of both filopodial and lamellipodial actin networks. To understand the molecular mechanisms underlying their cellular functions we used total internal reflection fluorescence microscopy to visualize VASP tetramers interacting with static and growing actin filaments in vitro. We observed multiple filament binding modes: (1) static side binding, (2) side binding with one-dimensional diffusion, and (3) processive barbed end tracking. Actin monomers antagonize side binding but promote high affinity (Kd = 9 nM) barbed end attachment. In low ionic strength buffers, VASP tetramers are weakly processive (Koff = 0.69 s−1) polymerases that deliver multiple actin monomers per barbed end–binding event and effectively antagonize filament capping. In higher ionic strength buffers, VASP requires profilin for effective polymerase and anti-capping activity. Based on our observations, we propose a mechanism that accounts for all three binding modes and provides a model for how VASP promotes actin filament assembly.

scholarly journals Single-molecule analysis reveals self assembly and nanoscale segregation of two distinct cavin subcomplexes on caveolae

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Yann Gambin ◽  
Nicholas Ariotti ◽  
Kerrie-Ann McMahon ◽  
Michele Bastiani ◽  
Emma Sierecki ◽  
...  
Keyword(s):  
Single Molecule ◽  
Self Assembly ◽  
Mammalian Cells ◽  
Protein Complexes ◽  
Building Blocks ◽  
Scaffolding Protein ◽  
Cell Extracts ◽  
Single Molecule Analysis ◽  
Exquisite Specificity

In mammalian cells three closely related cavin proteins cooperate with the scaffolding protein caveolin to form membrane invaginations known as caveolae. Here we have developed a novel single-molecule fluorescence approach to directly observe interactions and stoichiometries in protein complexes from cell extracts and from in vitro synthesized components. We show that up to 50 cavins associate on a caveola. However, rather than forming a single coat complex containing the three cavin family members, single-molecule analysis reveals an exquisite specificity of interactions between cavin1, cavin2 and cavin3. Changes in membrane tension can flatten the caveolae, causing the release of the cavin coat and its disassembly into separate cavin1-cavin2 and cavin1-cavin3 subcomplexes. Each of these subcomplexes contain 9 ± 2 cavin molecules and appear to be the building blocks of the caveolar coat. High resolution immunoelectron microscopy suggests a remarkable nanoscale organization of these separate subcomplexes, forming individual striations on the surface of caveolae.

scholarly journals Rho Kinase Regulates the Intracellular Micromechanical Response of Adherent Cells to Rho Activation

2004 ◽  
Vol 15 (7) ◽  
pp. 3475-3484 ◽  
Author(s):  
Thomas P. Kole ◽  
Yiider Tseng ◽  
Lawrence Huang ◽  
Joseph L. Katz ◽  
Denis Wirtz
Keyword(s):  
Mechanical Behavior ◽  
Molecular Mechanisms ◽  
Mechanical Response ◽  
Sol Gel ◽  
Critical Role ◽  
Rho Kinase ◽  
Small Gtpase ◽  
Cytoskeletal Proteins ◽  
Cellular Functions

Local sol-gel transitions of the cytoskeleton modulate cell shape changes, which are required for essential cellular functions, including motility and adhesion. In vitro studies using purified cytoskeletal proteins have suggested molecular mechanisms of regulation of cytoskeleton mechanics; however, the mechanical behavior of living cells and the signaling pathways by which it is regulated remains largely unknown. To address this issue, we used a nanoscale sensing method, intracellular microrheology, to examine the mechanical response of the cell to activation of the small GTPase Rho. We observe that the cytoplasmic stiffness and viscosity of serum-starved Swiss 3T3 cells transiently and locally enhances upon treatment with lysophosphatidic acid, and this mechanical behavior follows a trend similar to Rho activity. Furthermore, the time-dependent activation of Rho decreases the degree of microheterogeneity of the cytoplasm. Our results reveal fundamental differences between intracellular elasticity and cellular tension and suggest a critical role for Rho kinase in the regulation of intracellular mechanics.

scholarly journals Proximity-dependent proteomics reveals extensive interactions of Protocadherin-19 with regulators of Rho GTPases and the microtubule cytoskeleton

2020 ◽  
Author(s):  
Michelle R. Emond ◽  
Sayantanee Biswas ◽  
Matthew L. Morrow ◽  
James D. Jontes
Keyword(s):  
Nervous System ◽  
Behavioral Problems ◽  
Rho Gtpases ◽  
Protein Complexes ◽  
Epileptic Seizures ◽  
Centrosomal Protein ◽  
Surface Receptors ◽  
Rho Family Gtpases ◽  
Rho Family

AbstractProtocadherin-19 belongs to the cadherin family of cell surface receptors and has been shown to play essential roles in the development of the vertebrate nervous system. Mutations in human Protocadherin-19 (PCDH19) lead to PCDH19 Female-limited epilepsy (PCDH19 FLE) in humans, characterized by the early onset of epileptic seizures in children and a range of cognitive and behavioral problems in adults. Despite being considered the second most prevalent gene in epilepsy, very little is known about the intercellular pathways in which it participates. In order to characterize the protein complexes within which Pcdh19 functions, we generated Pcdh19-BioID fusion proteins and utilized proximity-dependent biotinylation to identify neighboring proteins. Proteomic identification and analysis revealed that the Pcdh19 interactome is enriched in proteins that regulate Rho family GTPases, microtubule binding proteins and proteins that regulate cell divisions. We cloned the centrosomal protein Nedd1 and the RacGEF Dock7 and verified their interactions with Pcdh19 in vitro. Our findings provide the first comprehensive insights into the interactome of Pcdh19, and provide a platform for future investigations into the cellular and molecular biology of this protein critical to the proper development of the nervous system.

scholarly journals Trans-toxin ion-sensitivity of charybdotoxin-blocked potassium-channels reveals unbinding transitional states

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Hans Moldenhauer ◽  
Ignacio Díaz-Franulic ◽  
Horacio Poblete ◽  
David Naranjo
Keyword(s):  
Conformational Changes ◽  
Molecular Mechanisms ◽  
Protein Complexes ◽  
Tight Binding ◽  
External Solution ◽  
Scorpion Venom ◽  
K Channels ◽  
Interaction Interface ◽  
Dynamic Stochastic

In silico and in vitro studies have made progress in understanding protein–protein complex formation; however, the molecular mechanisms for their dissociation are unclear. Protein–protein complexes, lasting from microseconds to years, often involve induced-fit, challenging computational or kinetic analysis. Charybdotoxin (CTX), a peptide from the Leiurus scorpion venom, blocks voltage-gated K+-channels in a unique example of binding/unbinding simplicity. CTX plugs the external mouth of K+-channels pore, stopping K+-ion conduction, without inducing conformational changes. Conflicting with a tight binding, we show that external permeant ions enhance CTX-dissociation, implying a path connecting the pore, in the toxin-bound channel, with the external solution. This sensitivity is explained if CTX wobbles between several bound conformations, producing transient events that restore the electrical and ionic trans-pore gradients. Wobbling may originate from a network of contacts in the interaction interface that are in dynamic stochastic equilibria. These partially-bound intermediates could lead to distinct, and potentially manipulable, dissociation pathways.

Sign in / Sign up

Export Citation Format

Share Document