scholarly journals Periodic actin structures in neuronal axons are required to maintain microtubules

2016 ◽  
Author(s):  
Yue Qu ◽  
Ines Hahn ◽  
Stephen Webb ◽  
Simon P. Pearce ◽  
Andreas Prokop
Keyword(s):  
Super Resolution ◽  
Close Correlation ◽  
Membrane Skeleton ◽  
Cortical Actin ◽  
Evolutionarily Conserved ◽  
Genes Encoding ◽  
Neuronal Processes ◽  
And Function ◽  
Super Resolution Microscopy ◽  
Actin Rings

SummaryAxons are the cable-like neuronal processes wiring the nervous system. They contain parallel bundles of microtubules as structural backbones, surrounded by regularly-spaced actin rings termed the periodic membrane skeleton (PMS). Despite being an evolutionarily-conserved, ubiquitous, highly-ordered feature of axons, the function of PMS is unknown. Here we studied PMS abundance, organisation and function, combining versatile Drosophila genetics with super-resolution microscopy and various functional readouts. Analyses with 11 different actin regulators and 3 actin-targeting drugs suggest PMS to contain short actin filaments which are depolymerisation resistant and sensitive to spectrin, adducin and nucleator deficiency - consistent with microscopy-derived models proposing PMS as specialised cortical actin. Upon actin removal we observed gaps in microtubule bundles, reduced microtubule polymerisation and reduced axon numbers suggesting a role of PMS in microtubule organisation. These effects become strongly enhanced when carried out in neurons lacking the microtubule-stabilising protein Short stop (Shot). Combining the aforementioned actin manipulations with Shot deficiency revealed a close correlation between PMS abundance and microtubule regulation, consistent with a model in which PMS-dependent microtubule polymerisation contributes to their maintenance in axons. We discuss potential implications of this novel PMS function along axon shafts for axon maintenance and regeneration.Significance statementAxons are cable-like neuronal processes that are up to a meter long in humans. These delicate structures often need to be maintained for an organism’s lifetime, i.e. up to a century in humans. Unsurprisingly, we gradually lose about 50% of axons as we age. Bundles of microtubules form the structural backbones and highways for life-sustaining transport within axons, and maintenance of these bundles is essential for axonal longevity. However, the mechanisms which actively maintain axonal microtubules are poorly understood. Here we identify cortical actin as an important factor maintaining microtubule polymerisation in axons. This finding provides potential explanations for the previously identified, but unexplained, links between mutations in genes encoding cortical actin regulators and neurodegeneration.

scholarly journals Periodic actin structures in neuronal axons are required to maintain microtubules

2017 ◽  
Vol 28 (2) ◽  
pp. 296-308 ◽  
Author(s):  
Yue Qu ◽  
Ines Hahn ◽  
Stephen E.D. Webb ◽  
Simon P. Pearce ◽  
Andreas Prokop
Keyword(s):  
Close Correlation ◽  
Membrane Skeleton ◽  
Cortical Actin ◽  
Microtubule Organization ◽  
Superresolution Microscopy ◽  
Microtubule Polymerization ◽  
Evolutionarily Conserved ◽  
Neuronal Processes ◽  
And Function ◽  
Actin Rings

Axons are cable-like neuronal processes wiring the nervous system. They contain parallel bundles of microtubules as structural backbones, surrounded by regularly spaced actin rings termed the periodic membrane skeleton (PMS). Despite being an evolutionarily conserved, ubiquitous, highly ordered feature of axons, the function of PMS is unknown. Here we studied PMS abundance, organization, and function, combining versatile Drosophila genetics with superresolution microscopy and various functional readouts. Analyses with 11 actin regulators and three actin-targeting drugs suggest that PMS contains short actin filaments that are depolymerization resistant and sensitive to spectrin, adducin, and nucleator deficiency, consistent with microscopy-derived models proposing PMS as specialized cortical actin. Upon actin removal, we observed gaps in microtubule bundles, reduced microtubule polymerization, and reduced axon numbers, suggesting a role of PMS in microtubule organization. These effects become strongly enhanced when carried out in neurons lacking the microtubule-stabilizing protein Short stop (Shot). Combining the aforementioned actin manipulations with Shot deficiency revealed a close correlation between PMS abundance and microtubule regulation, consistent with a model in which PMS-dependent microtubule polymerization contributes to their maintenance in axons. We discuss potential implications of this novel PMS function along axon shafts for axon maintenance and regeneration.

Super-Resolution Microscopy in Studying the Structure and Function of the Cell Nucleus

Acta Naturae ◽  
2017 ◽  
Vol 9 (4) ◽  
pp. 42-51
Author(s):  
S. S. Ryabichko ◽  
◽  
A. N. Ibragimov ◽  
L. A. Lebedeva ◽  
E. N. Kozlov ◽  
...  
Keyword(s):  
Cell Nucleus ◽  
Super Resolution ◽  
Structure And Function ◽  
And Function ◽  
Super Resolution Microscopy

scholarly journals Regulated protein stabilization underpins the functional interplay among basal body components in Trypanosoma brucei

2019 ◽  
Vol 295 (3) ◽  
pp. 729-742
Author(s):  
Kieu T. M. Pham ◽  
Ziyin Li
Keyword(s):  
Trypanosoma Brucei ◽  
Basal Body ◽  
Super Resolution ◽  
Specific Protein ◽  
Protein Stabilization ◽  
Structured Illumination ◽  
Human Parasite ◽  
Evolutionarily Conserved ◽  
Body Components ◽  
Super Resolution Microscopy

The basal body in the human parasite Trypanosoma brucei is structurally equivalent to the centriole in animals and functions in the nucleation of axonemal microtubules in the flagellum. T. brucei lacks many evolutionarily conserved centriolar protein homologs and constructs the basal body through unknown mechanisms. Two evolutionarily conserved centriole/basal body cartwheel proteins, TbSAS-6 and TbBLD10, and a trypanosome-specific protein, BBP65, play essential roles in basal body biogenesis in T. brucei, but how they cooperate in the regulation of basal body assembly remains elusive. Here using RNAi, endogenous epitope tagging, immunofluorescence microscopy, and 3D-structured illumination super-resolution microscopy, we identified a new trypanosome-specific protein named BBP164 and found that it has an essential role in basal body biogenesis in T. brucei. Further investigation of the functional interplay among BBP164 and the other three regulators of basal body assembly revealed that BBP164 and BBP65 are interdependent for maintaining their stability and depend on TbSAS-6 and TbBLD10 for their stabilization in the basal body. Additionally, TbSAS-6 and TbBLD10 are independent from each other and from BBP164 and BBP65 for maintaining their stability in the basal body. These findings demonstrate that basal body cartwheel proteins are required for stabilizing other basal body components and uncover that regulation of protein stability is an unusual control mechanism for assembly of the basal body in T. brucei.

scholarly journals Remodelling of Cortical Actin Where Lytic Granules Dock at Natural Killer Cell Immune Synapses Revealed by Super-Resolution Microscopy

PLoS Biology ◽  
2011 ◽  
Vol 9 (9) ◽  
pp. e1001152 ◽  
Author(s):  
Alice C. N. Brown ◽  
Stephane Oddos ◽  
Ian M. Dobbie ◽  
Juha-Matti Alakoskela ◽  
Richard M. Parton ◽  
...  
Keyword(s):  
Natural Killer Cell ◽  
Natural Killer ◽  
Killer Cell ◽  
Super Resolution ◽  
Cortical Actin ◽  
Lytic Granules ◽  
Immune Synapses ◽  
Super Resolution Microscopy

scholarly journals Ultrastructure of the axonal periodic scaffold reveals a braid-like organization of actin rings

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Stéphane Vassilopoulos ◽  
Solène Gibaud ◽  
Angélique Jimenez ◽  
Ghislaine Caillol ◽  
Christophe Leterrier
Keyword(s):  
Actin Filaments ◽  
Myosin Light Chain ◽  
Super Resolution ◽  
Ultrastructural Level ◽  
Ankyrin G ◽  
Molecular Arrangement ◽  
Resolution Electron ◽  
Super Resolution Microscopy ◽  
Actin Rings ◽  
Cortical Cytoskeleton

AbstractRecent super-resolution microscopy studies have unveiled a periodic scaffold of actin rings regularly spaced by spectrins under the plasma membrane of axons. However, ultrastructural details are unknown, limiting a molecular and mechanistic understanding of these enigmatic structures. Here, we combine platinum-replica electron and optical super-resolution microscopy to investigate the cortical cytoskeleton of axons at the ultrastructural level. Immunogold labeling and correlative super-resolution/electron microscopy allow us to unambiguously resolve actin rings as braids made of two long, intertwined actin filaments connected by a dense mesh of aligned spectrins. This molecular arrangement contrasts with the currently assumed model of actin rings made of short, capped actin filaments. Along the proximal axon, we resolved the presence of phospho-myosin light chain and the scaffold connection with microtubules via ankyrin G. We propose that braided rings explain the observed stability of the actin-spectrin scaffold and ultimately participate in preserving the axon integrity.

scholarly journals Ultrastructure of the axonal periodic scaffold reveals a braid-like organization of actin rings

2019 ◽  
Author(s):  
Stéphane Vassilopoulos ◽  
Solène Gibaud ◽  
Angélique Jimenez ◽  
Ghislaine Caillol ◽  
Christophe Leterrier
Keyword(s):  
Actin Filaments ◽  
Myosin Light Chain ◽  
Super Resolution ◽  
Ultrastructural Level ◽  
Ankyrin G ◽  
Molecular Arrangement ◽  
Resolution Electron ◽  
Super Resolution Microscopy ◽  
Actin Rings ◽  
Cortical Cytoskeleton

Recent super-resolution microscopy studies have unveiled a periodic scaffold of actin rings regularly spaced by spectrins under the plasma membrane of axons. However, ultrastructural details are unknown, limiting a molecular and mechanistic understanding of these enigmatic structures. Here, we combine platinum-replica electron and optical super-resolution microscopy to investigate the cortical cytoskeleton of axons at the ultrastructural level. Immunogold labeling and correlative super-resolution/electron microscopy allow us to unambiguously resolve actin rings as braids made of two long, intertwined actin filaments connected by a dense mesh of aligned spectrins. This molecular arrangement contrasts with the currently assumed model of actin rings made of short, capped actin filaments. Along the proximal axon, we resolved the presence of phospho-myosin light chain and the scaffold connection with microtubules via ankyrin G. We propose that braided rings explain the observed stability of the actin-spectrin scaffold and ultimately participate in preserving the axon integrity.

scholarly journals Microscope-AOtools: A generalised adaptive optics implementation

2020 ◽  
Author(s):  
Nicholas Hall ◽  
Josh Titlow ◽  
Martin J. Booth ◽  
Ian M. Dobbie
Keyword(s):  
Image Quality ◽  
Adaptive Optics ◽  
Super Resolution ◽  
Biological Imaging ◽  
New Techniques ◽  
Reduce Image Quality ◽  
Set Up ◽  
And Function ◽  
Microscopy Techniques ◽  
Super Resolution Microscopy

AbstractMicroscope-AOtools is a software package which allows for a simple, robust and generalised implementation of adaptive optics (AO) elements. It contains all the necessary methods for set-up, calibration, and aberration correction which are simple to use and function in a robust manner. Aberrations arising from sources such as sample hetero-geneity and refractive index mismatches are constant problems in biological imaging. These aberrations reduce image quality and the achievable depth of imaging, particularly in super-resolution microscopy techniques. AO technology has been proven to be effective in correcting for these aberrations and thereby improving the image quality. However, it has not been widely adopted by the biological imaging community due, in part, to difficulty in set-up and operation of AO, particularly by non-specialist users. Microscope-AOtools offers a robust, easy-to-use implementation of the essential methods for set-up and use of AO techniques. These methods are constructed in a generalised manner that can utilise a range of adaptive optics elements, wavefront sensing techniques and sensorless AO correction methods. Furthermore, the methods are designed to be easily extensible as new techniques arise, leading to a streamlined pipeline for new AO technology and techniques to be adopted by the wider microscopy community.

scholarly journals The membrane periodic skeleton is an actomyosin network that regulates axonal diameter and conduction

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Ana Rita Costa ◽  
Sara C Sousa ◽  
Rita Pinto-Costa ◽  
José C Mateus ◽  
Cátia DF Lopes ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Myosin Ii ◽  
Super Resolution ◽  
Loss Of Function ◽  
Axon Diameter ◽  
Heavy Chains ◽  
Axonal Diameter ◽  
Muscle Myosin ◽  
Super Resolution Microscopy ◽  
Actin Rings

Neurons have a membrane periodic skeleton (MPS) composed of actin rings interconnected by spectrin. Here, combining chemical and genetic gain- and loss-of-function assays, we show that in rat hippocampal neurons the MPS is an actomyosin network that controls axonal expansion and contraction. Using super-resolution microscopy, we analyzed the localization of axonal non-muscle myosin II (NMII). We show that active NMII light chains are colocalized with actin rings and organized in a circular periodic manner throughout the axon shaft. In contrast, NMII heavy chains are mostly positioned along the longitudinal axonal axis, being able to crosslink adjacent rings. NMII filaments can play contractile or scaffolding roles determined by their position relative to actin rings and activation state. We also show that MPS destabilization through NMII inactivation affects axonal electrophysiology, increasing action potential conduction velocity. In summary, our findings open new perspectives on axon diameter regulation, with important implications in neuronal biology.

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