scholarly journals Structural and Functional Modulation of Perineuronal Nets: In Search of Important Players with Highlight on Tenascins

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1345
Author(s):  
Ana Jakovljević ◽  
Milena Tucić ◽  
Michaela Blažiková ◽  
Andrej Korenić ◽  
Yannis Missirlis ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Brain Plasticity ◽  
Super Resolution ◽  
Perineuronal Nets ◽  
Optimal Conditions ◽  
Neuronal Function ◽  
Specialized Form ◽  
Functional Modulation ◽  
Super Resolution Microscopy ◽  
The Brain

The extracellular matrix (ECM) of the brain plays a crucial role in providing optimal conditions for neuronal function. Interactions between neurons and a specialized form of ECM, perineuronal nets (PNN), are considered a key mechanism for the regulation of brain plasticity. Such an assembly of interconnected structural and regulatory molecules has a prominent role in the control of synaptic plasticity. In this review, we discuss novel ways of studying the interplay between PNN and its regulatory components, particularly tenascins, in the processes of synaptic plasticity, mechanotransduction, and neurogenesis. Since enhanced neuronal activity promotes PNN degradation, it is possible to study PNN remodeling as a dynamical change in the expression and organization of its constituents that is reflected in its ultrastructure. The discovery of these subtle modifications is enabled by the development of super-resolution microscopy and advanced methods of image analysis.

scholarly journals pIgR and PECAM-1 bind to pneumococcal adhesins RrgA and PspC mediating bacterial brain invasion

2017 ◽  
Vol 214 (6) ◽  
pp. 1619-1630 ◽  
Author(s):  
Federico Iovino ◽  
Joo-Yeon Engelen-Lee ◽  
Matthijs Brouwer ◽  
Diederik van de Beek ◽  
Arie van der Ende ◽  
...  
Keyword(s):  
Pneumococcal Meningitis ◽  
Case Fatality ◽  
Super Resolution ◽  
Stimulated Emission ◽  
Brain Invasion ◽  
Immunoglobulin Receptor ◽  
Platelet Endothelial Cell Adhesion ◽  
Lower Extent ◽  
Super Resolution Microscopy ◽  
The Brain

Streptococcus pneumoniae is the main cause of bacterial meningitis, a life-threating disease with a high case fatality rate despite treatment with antibiotics. Pneumococci cause meningitis by invading the blood and penetrating the blood–brain barrier (BBB). Using stimulated emission depletion (STED) super-resolution microscopy of brain biopsies from patients who died of pneumococcal meningitis, we observe that pneumococci colocalize with the two BBB endothelial receptors: polymeric immunoglobulin receptor (pIgR) and platelet endothelial cell adhesion molecule (PECAM-1). We show that the major adhesin of the pneumococcal pilus-1, RrgA, binds both receptors, whereas the choline binding protein PspC binds, but to a lower extent, only pIgR. Using a bacteremia-derived meningitis model and mutant mice, as well as antibodies against the two receptors, we prevent pneumococcal entry into the brain and meningitis development. By adding antibodies to antibiotic (ceftriaxone)-treated mice, we further reduce the bacterial burden in the brain. Our data suggest that inhibition of pIgR and PECAM-1 has the potential to prevent pneumococcal meningitis.

scholarly journals Dynamics and nanoscale organization of the postsynaptic endocytic zone at excitatory synapses

2021 ◽  
Author(s):  
Lisa A.E. Catsburg ◽  
Manon Westra ◽  
Annemarie M. L. van Schaik ◽  
Harold D. MacGillavry
Keyword(s):  
Synaptic Plasticity ◽  
Actin Cytoskeleton ◽  
Glutamate Receptors ◽  
Super Resolution ◽  
Live Cell ◽  
Excitatory Synapses ◽  
Membrane Interactions ◽  
Synaptic Receptors ◽  
Microscopy Techniques ◽  
Super Resolution Microscopy

ABSTRACTAt postsynaptic sites of neurons, a prominent clathrin-coated structure, the endocytic zone (EZ), controls the trafficking of glutamate receptors and is essential for synaptic plasticity. Despite its importance, little is known about how this clathrin structure is organized to mediate endocytosis. We used live-cell and super-resolution microscopy techniques to reveal the dynamic organization of this poorly understood clathrin structure. We found that a subset of endocytic proteins only transiently appeared at postsynaptic sites. In contrast, other proteins, including Eps15, intersectin1L, and β2-adaptin, were persistently enriched and partitioned at the edge of the EZ. We found that uncoupling the EZ from the synapse led to the loss of most of these components, while disrupting the actin cytoskeleton or AP2-membrane interactions did not alter EZ positioning. We conclude that the EZ is a stable, highly organized molecular platform where components are differentially recruited and positioned to orchestrate the endocytosis of synaptic receptors.

scholarly journals Super-resolution imaging reveals α-synuclein seeded aggregation in SH-SY5Y cells

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jason C. Sang ◽  
Eric Hidari ◽  
Georg Meisl ◽  
Rohan T. Ranasinghe ◽  
Maria Grazia Spillantini ◽  
...  
Keyword(s):  
Protein Aggregation ◽  
Self Assembly ◽  
Super Resolution ◽  
Quantitative Information ◽  
Protein Homeostasis ◽  
Protective Response ◽  
Resolution Imaging ◽  
Key Steps ◽  
Super Resolution Microscopy ◽  
The Brain

AbstractAggregation of α-synuclein (α-syn) is closely linked to Parkinson’s disease (PD) and the related synucleinopathies. Aggregates spread through the brain during the progression of PD, but the mechanism by which this occurs is still not known. One possibility is a self-propagating, templated-seeding mechanism, but this cannot be established without quantitative information about the efficiencies and rates of the key steps in the cellular process. To address this issue, we imaged the uptake and seeding of unlabeled exogenous α-syn fibrils by SH-SY5Y cells and the resulting secreted aggregates, using super-resolution microscopy. Externally-applied fibrils very inefficiently induced self-assembly of endogenous α-syn in a process accelerated by the proteasome. Seeding resulted in the increased secretion of nanoscopic aggregates (mean 35 nm diameter), of both α-syn and Aβ. Our results suggest that cells respond to seed-induced disruption of protein homeostasis predominantly by secreting nanoscopic aggregates; this mechanism may therefore be an important protective response by cells to protein aggregation.

scholarly journals SpineJ : A software tool for quantitative analysis of nanoscale spine morphology

2019 ◽  
Author(s):  
Florian Levet ◽  
Jan Tønnesen ◽  
Valentin Nägerl ◽  
Jean-Baptiste Sibarita
Keyword(s):  
Super Resolution ◽  
Software Tool ◽  
Neuronal Function ◽  
Spine Morphology ◽  
Nanoscale Structures ◽  
Structural Details ◽  
User Friendly ◽  
Super Resolution Microscopy ◽  
Friendly Graphical User Interface ◽  
Imagej Plugin

AbstractSuper-resolution microscopy provides diffraction-unlimited optical access to the intricate morphology of neurons in living brain tissue, resolving their finest structural details, which are critical for neuronal function. However, as existing image analysis software tools have been developed for diffraction-limited images, they are generally not well suited for quantifying nanoscale structures like dendritic spines. We present SpineJ, a semi-automatic ImageJ plugin that is specifically designed for this purpose. SpineJ comes with an intuitive and user-friendly graphical user interface, facilitating fast, accurate, and unbiased analysis of spine morphology.

scholarly journals Extracellular matrix remodeling through endocytosis and resurfacing of Tenascin-R

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tal M. Dankovich ◽  
Rahul Kaushik ◽  
Linda H. M. Olsthoorn ◽  
Gabriel Cassinelli Petersen ◽  
Philipp Emanuel Giro ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Secondary Ion Mass Spectrometry ◽  
Brain Slices ◽  
Super Resolution ◽  
Matrix Remodeling ◽  
Neuronal Function ◽  
Ecm Remodeling ◽  
Activity Dependent ◽  
The Brain ◽  
Secondary Ion

AbstractThe brain extracellular matrix (ECM) consists of extremely long-lived proteins that assemble around neurons and synapses, to stabilize them. The ECM is thought to change only rarely, in relation to neuronal plasticity, through ECM proteolysis and renewed protein synthesis. We report here an alternative ECM remodeling mechanism, based on the recycling of ECM molecules. Using multiple ECM labeling and imaging assays, from super-resolution optical imaging to nanoscale secondary ion mass spectrometry, both in culture and in brain slices, we find that a key ECM protein, Tenascin-R, is frequently endocytosed, and later resurfaces, preferentially near synapses. The TNR molecules complete this cycle within ~3 days, in an activity-dependent fashion. Interfering with the recycling process perturbs severely neuronal function, strongly reducing synaptic vesicle exo- and endocytosis. We conclude that the neuronal ECM can be remodeled frequently through mechanisms that involve endocytosis and recycling of ECM proteins.

scholarly journals Serotonin-specific neurons differentiated from human iPSCs form distinct subtypes with synaptic protein assembly

2021 ◽  
Vol 128 (2) ◽  
pp. 225-241
Author(s):  
Charline Jansch ◽  
Georg C. Ziegler ◽  
Andrea Forero ◽  
Sina Gredy ◽  
Sina Wäldchen ◽  
...  
Keyword(s):  
Tryptophan Hydroxylase ◽  
Neuronal Cell ◽  
Super Resolution ◽  
Neuropsychiatric Disorders ◽  
Human Ipscs ◽  
Heterogeneous Nature ◽  
Induced Pluripotent ◽  
Super Resolution Microscopy ◽  
The Brain

AbstractHuman induced pluripotent stem cells (hiPSCs) have revolutionized the generation of experimental disease models, but the development of protocols for the differentiation of functionally active neuronal subtypes with defined specification is still in its infancy. While dysfunction of the brain serotonin (5-HT) system has been implicated in the etiology of various neuropsychiatric disorders, investigation of functional human 5-HT specific neurons in vitro has been restricted by technical limitations. We describe an efficient generation of functionally active neurons from hiPSCs displaying 5-HT specification by modification of a previously reported protocol. Furthermore, 5-HT specific neurons were characterized using high-end fluorescence imaging including super-resolution microscopy in combination with electrophysiological techniques. Differentiated hiPSCs synthesize 5-HT, express specific markers, such as tryptophan hydroxylase 2 and 5-HT transporter, and exhibit an electrophysiological signature characteristic of serotonergic neurons, with spontaneous rhythmic activities, broad action potentials and large afterhyperpolarization potentials. 5-HT specific neurons form synapses reflected by the expression of pre- and postsynaptic proteins, such as Bassoon and Homer. The distribution pattern of Bassoon, a marker of the active zone along the soma and extensions of neurons, indicates functionality via volume transmission. Among the high percentage of 5-HT specific neurons (~ 42%), a subpopulation of CDH13 + cells presumably designates dorsal raphe neurons. hiPSC-derived 5-HT specific neuronal cell cultures reflect the heterogeneous nature of dorsal and median raphe nuclei and may facilitate examining the association of serotonergic neuron subpopulations with neuropsychiatric disorders.

scholarly journals Evidence of Presynaptic Localization and Function of the c-Jun N-Terminal Kinase

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Silvia Biggi ◽  
Lucia Buccarello ◽  
Alessandra Sclip ◽  
Pellegrino Lippiello ◽  
Noemi Tonna ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Physiological Role ◽  
Super Resolution ◽  
Snare Complex ◽  
Snare Proteins ◽  
Electrophysiological Recordings ◽  
Presynaptic Site ◽  
Presynaptic Nmda Receptors ◽  
And Function ◽  
Super Resolution Microscopy

The c-Jun N-terminal kinase (JNK) is part of a stress signalling pathway strongly activated by NMDA-stimulation and involved in synaptic plasticity. Many studies have been focused on the post-synaptic mechanism of JNK action, and less is known about JNK presynaptic localization and its physiological role at this site. Here we examined whether JNK is present at the presynaptic site and its activity after presynaptic NMDA receptors stimulation. By using N-SIM Structured Super Resolution Microscopy as well as biochemical approaches, we demonstrated that presynaptic fractions contained significant amount of JNK protein and its activated form. By means of modelling design, we found that JNK, via the JBD domain, acts as a physiological effector on T-SNARE proteins; then using biochemical approaches we demonstrated the interaction between Syntaxin-1-JNK, Syntaxin-2-JNK, and Snap25-JNK. In addition, taking advance of the specific JNK inhibitor peptide, D-JNKI1, we defined JNK action on the SNARE complex formation. Finally, electrophysiological recordings confirmed the role of JNK in the presynaptic modulation of vesicle release. These data suggest that JNK-dependent phosphorylation of T-SNARE proteins may have an important functional role in synaptic plasticity.

scholarly journals Neuronal Localization of SENP Proteins with Super Resolution Microscopy

2020 ◽  
Vol 10 (11) ◽  
pp. 778
Author(s):  
Luca Colnaghi ◽  
Andrea Conz ◽  
Luca Russo ◽  
Clara A. Musi ◽  
Luana Fioriti ◽  
...  
Keyword(s):  
Super Resolution ◽  
Structured Illumination ◽  
Neuronal Function ◽  
Structured Illumination Microscopy ◽  
Synaptic Markers ◽  
Specific Protease ◽  
Fine Regulation ◽  
And Function ◽  
Super Resolution Microscopy ◽  
First Time

SUMOylation of proteins plays a key role in modulating neuronal function. For this reason, the balance between protein SUMOylation and deSUMOylation requires fine regulation to guarantee the homeostasis of neural tissue. While extensive research has been carried out on the localization and function of small ubiquitin-related modifier (SUMO) variants in neurons, less attention has been paid to the SUMO-specific isopeptidases that constitute the human SUMO-specific isopeptidase (SENP)/Ubiquitin-Specific Protease (ULP) cysteine protease family (SENP1-3 and SENP5-7). Here, for the first time, we studied the localization of SENP1, SENP6, and SENP7 in cultured hippocampal primary neurons at a super resolution detail level, with structured illumination microscopy (SIM). We found that the deSUMOylases partially colocalize with pre- and post-synaptic markers such as synaptophysin and drebrin. Thus, further confirming the presence with synaptic markers of the negative regulators of the SUMOylation machinery.

scholarly journals Microglia alter the threshold of spreading depolarization and related potassium uptake in the mouse brain

2020 ◽  
Vol 40 (1_suppl) ◽  
pp. S67-S80 ◽  
Author(s):  
Dániel P Varga ◽  
Ákos Menyhárt ◽  
Balázs Pósfai ◽  
Eszter Császár ◽  
Nikolett Lénárt ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Super Resolution ◽  
Potassium Uptake ◽  
Extracellular Potassium ◽  
Spreading Depolarization ◽  
Selective Elimination ◽  
Intact Brain ◽  
Super Resolution Microscopy ◽  
The Brain

Selective elimination of microglia from the brain was shown to dysregulate neuronal Ca2+ signaling and to reduce the incidence of spreading depolarization (SD) during cerebral ischemia. However, the mechanisms through which microglia interfere with SD remained unexplored. Here, we identify microglia as essential modulators of the induction and evolution of SD in the physiologically intact brain in vivo. Confocal- and super-resolution microscopy revealed that a series of SDs induced rapid morphological changes in microglia, facilitated microglial process recruitment to neurons and increased the density of P2Y12 receptors (P2Y12R) on recruited microglial processes. In line with this, depolarization and hyperpolarization during SD were microglia- and P2Y12R-dependent. An absence of microglia was associated with altered potassium uptake after SD and increased the number of c-fos-positive neurons, independently of P2Y12R. Thus, the presence of microglia is likely to be essential to maintain the electrical elicitation threshold and to support the full evolution of SD, conceivably by interfering with the extracellular potassium homeostasis of the brain through sustaining [K+]e re-uptake mechanisms.

scholarly journals Erasing Synapses in Sleep: Is It Time to Be SHY?

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Marcos Gabriel Frank
Keyword(s):  
Drosophila Melanogaster ◽  
Synaptic Plasticity ◽  
Functional Significance ◽  
Brain Plasticity ◽  
Cellular Mechanism ◽  
Homeostatic Regulation ◽  
Synaptic Homeostasis ◽  
Underlying Mechanisms ◽  
The Brain ◽  
Lines Of Evidence

Converging lines of evidence strongly support a role for sleep in brain plasticity. An elegant idea that may explain how sleep accomplishes this role is the “synaptic homeostasis hypothesis (SHY).” According to SHY, sleep promotes net synaptic weakening which offsets net synaptic strengthening that occurs during wakefulness. SHY is intuitively appealing because it relates the homeostatic regulation of sleep to an important function (synaptic plasticity). SHY has also received important experimental support from recent studies inDrosophila melanogaster. There remain, however, a number of unanswered questions about SHY. What is the cellular mechanism governing SHY? How does it fit with what we know about plasticity mechanisms in the brain? In this review, I discuss the evidence and theory of SHY in the context of what is known about Hebbian and non-Hebbian synaptic plasticity. I conclude that while SHY remains an elegant idea, the underlying mechanisms are mysterious and its functional significance unknown.

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