scholarly journals Neto-α controls synapse organization and homeostasis at the Drosophila neuromuscular junction

2019 ◽  
Author(s):  
Tae Hee Han ◽  
Rosario Vicidomini ◽  
Cathy Isaura Ramos ◽  
Qi Wang ◽  
Peter Nguyen ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Motor Neurons ◽  
Neurotransmitter Release ◽  
Cell Biology ◽  
Expression Patterns ◽  
Dependent Manner ◽  
Independent Function ◽  
Postsynaptic Receptors ◽  
Auxiliary Protein ◽  
And Function

SummaryGlutamate receptor auxiliary proteins control receptor distribution and function, ultimately controlling synapse assembly, maturation and plasticity. At the Drosophila neuromuscular junction (NMJ), a synapse with both pre- and post-synaptic kainate-type glutamate receptors (KARs), we show that the auxiliary protein Neto evolved functionally distinct isoforms to modulate synapse development and homeostasis. Using genetics, cell biology and electrophysiology we demonstrate that Neto-α functions on both sides of the NMJ. In muscle, Neto-α limits the size of the postsynaptic receptors field. In motor neurons, Neto-α controls neurotransmitter release in a KAR-dependent manner. Furthermore, Neto-α is both required and sufficient for the presynaptic increase in neurotransmitter release in response to reduced postsynaptic sensitivity. This KAR-independent function of Neto-α is involved in activity-induced cytomatrix remodeling. We propose that Drosophila ensured NMJ functionality by acquiring two Neto isoforms with differential expression patterns and activities.

scholarly journals Tenectin recruits integrin to stabilize bouton architecture and regulate vesicle release at the Drosophila neuromuscular junction

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Qi Wang ◽  
Tae Hee Han ◽  
Peter Nguyen ◽  
Michal Jarnik ◽  
Mihaela Serpe
Keyword(s):  
Neuromuscular Junction ◽  
Motor Neurons ◽  
Synaptic Cleft ◽  
Membrane Skeleton ◽  
Biologically Active ◽  
Striated Muscles ◽  
Local Engagement ◽  
Synaptic Junctions ◽  
Synaptic Boutons ◽  
And Function

Assembly, maintenance and function of synaptic junctions depend on extracellular matrix (ECM) proteins and their receptors. Here we report that Tenectin (Tnc), a Mucin-type protein with RGD motifs, is an ECM component required for the structural and functional integrity of synaptic specializations at the neuromuscular junction (NMJ) in Drosophila. Using genetics, biochemistry, electrophysiology, histology and electron microscopy, we show that Tnc is secreted from motor neurons and striated muscles and accumulates in the synaptic cleft. Tnc selectively recruits αPS2/βPS integrin at synaptic terminals, but only the cis Tnc/integrin complexes appear to be biologically active. These complexes have distinct pre- and postsynaptic functions, mediated at least in part through the local engagement of the spectrin-based membrane skeleton: the presynaptic complexes control neurotransmitter release, while postsynaptic complexes ensure the size and architectural integrity of synaptic boutons. Our study reveals an unprecedented role for integrin in the synaptic recruitment of spectrin-based membrane skeleton.

scholarly journals MiR-23~27~24–mediated control of humoral immunity reveals a TOX-driven regulatory circuit in follicular helper T cell differentiation

2019 ◽  
Vol 5 (12) ◽  
pp. eaaw1715 ◽  
Author(s):  
Cheng-Jang Wu ◽  
Sunglim Cho ◽  
Hsi-Yuan Huang ◽  
Chun-Hao Lu ◽  
Jasmin Russ ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Humoral Immunity ◽  
Cell Biology ◽  
Dependent Manner ◽  
Cell Responses ◽  
Follicular Helper ◽  
Regulatory Circuit ◽  
Follicular Helper T Cell ◽  
Immune Challenges ◽  
And Function

Follicular helper T (TFH) cells are essential for generating protective humoral immunity. To date, microRNAs (miRNAs) have emerged as important players in regulating TFH cell biology. Here, we show that loss of miR-23~27~24 clusters in T cells resulted in elevated TFH cell frequencies upon different immune challenges, whereas overexpression of this miRNA family led to reduced TFH cell responses. Mechanistically, miR-23~27~24 clusters coordinately control TFH cells through targeting a network of genes that are crucial for TFH cell biology. Among them, thymocyte selection–associated HMG-box protein (TOX) was identified as a central transcription regulator in TFH cell development. TOX is highly up-regulated in both mouse and human TFH cells in a BCL6-dependent manner. In turn, TOX promotes the expression of multiple molecules that play critical roles in TFH cell differentiation and function. Collectively, our results establish a key miRNA regulon that maintains optimal TFH cell responses for resultant humoral immunity.

scholarly journals Murine muscle stem cell response to perturbations of the neuromuscular junction are attenuated with aging

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Jacqueline Larouche ◽  
Mahir Mohiuddin ◽  
Jeongmoon J Choi ◽  
Peter J Ulintz ◽  
Paula M Fraczek ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Motor Neurons ◽  
Neuromuscular Diseases ◽  
Lineage Tracing ◽  
Genetic Rescue ◽  
Muscle Stem Cells ◽  
Transgenic Murine Model ◽  
And Function ◽  
The Relationship

During aging and neuromuscular diseases, there is a progressive loss of skeletal muscle volume and function impacting mobility and quality of life. Muscle loss is often associated with denervation and a loss of resident muscle stem cells (satellite cells or MuSCs), however, the relationship between MuSCs and innervation has not been established. Herein, we administered severe neuromuscular trauma to a transgenic murine model that permits MuSC lineage tracing. We show that a subset of MuSCs specifically engraft in a position proximal to the neuromuscular junction (NMJ), the synapse between myofibers and motor neurons, in healthy young adult muscles. In aging and in a mouse model of neuromuscular degeneration (Cu/Zn superoxide dismutase knockout – Sod1-/-), this localized engraftment behavior was reduced. Genetic rescue of motor neurons in Sod1-/- mice reestablished integrity of the NMJ in a manner akin to young muscle and partially restored MuSC ability to engraft into positions proximal to the NMJ. Using single cell RNA-sequencing of MuSCs isolated from aged muscle, we demonstrate that a subset of MuSCs are molecularly distinguishable from MuSCs responding to myofiber injury and share similarity to synaptic myonuclei. Collectively, these data reveal unique features of MuSCs that respond to synaptic perturbations caused by aging and other stressors.

scholarly journals Tudor staphylococcal nuclease acts as a docking platform for stress granule components in Arabidopsis thaliana

2020 ◽  
Author(s):  
Emilio Gutierrez-Beltran ◽  
Pernilla H. Elander ◽  
Kerstin Dalman ◽  
Jose Luis Crespo ◽  
Panagiotis N. Moschou ◽  
...  
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Cell Biology ◽  
Gene Expression Regulation ◽  
De Novo ◽  
Staphylococcal Nuclease ◽  
Fine Tuning ◽  
Dependent Manner ◽  
Stress Dependent ◽  
And Function

SUMMARYAdaptation to stress depends on the modulation of gene expression. Regulation of mRNA stability and degradation in stress granules (SGs), - cytoplasmic membraneless organelles composed of messenger ribonucleoprotein (mRNP) complexes, - plays an important role in fine-tuning of gene expression. In addition, SG formation can modulate stress signaling pathways by protein sequestration. Molecular composition, structure, and function of SGs in plants remain obscure. Recently, we established Tudor Staphylococcal Nuclease (TSN or Tudor-SN; also known as SND1) as integral component of SGs in Arabidopsis thaliana. Here, we combined purification of TSN interactome with cell biology, reverse genetics and bioinformatics to study composition and function of SGs in plants. We found that under both normal (in the absence of stress) and stress conditions TSN interactome is enriched in the homologues of known mammalian and yeast SG proteins, in addition to novel or plant-specific SG components. We estimate that upon stress perception, approximately half of TSN interactors are recruited to SGs de novo, in a stress-dependent manner, while another half represent a dense protein-protein interaction network pre-formed before onset of stress. Almost all TSN-interacting proteins are moderately or highly disordered and approximately 20% of them are predisposed for liquid-liquid phase separation (LLPS). This suggests that plant SGs, similarly to mammalian and yeast counterparts, are multicomponent viscous liquid droplets. Finally, we have discovered that evolutionary conserved SNF1-related protein kinase 1 (SnRK1) interacts with TSN in heat-induced SGs and that SnRK1 activation critically depends on the presence of TSN and formation of SGs. Altogether, our results establish TSN as a docking platform for SG-associated proteins and important stress signal mediator in plants.

scholarly journals Properties of Glial Cell at the Neuromuscular Junction are Incompatible with synaptic repair in the SOD1G37R ALS mouse model

2020 ◽  
Author(s):  
Martineau Éric ◽  
Danielle Arbour ◽  
Joanne Vallée ◽  
Robitaille Richard
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Neuromuscular Junction ◽  
Motor Unit ◽  
Glial Cell ◽  
Glial Cells ◽  
Motor Neurons ◽  
Nerve Terminal ◽  
Dependent Manner ◽  
Repair Mechanisms ◽  
Lateral Sclerosis

ABSTRACTAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting motoneurons in a motor-unit (MU) dependent manner. Glial dysfunction contributes to numerous aspects of the disease. At the neuromuscular junction (NMJ), early alterations in perisynaptic Schwann cell (PSC), glial cells at this synapse, may impact their ability to regulate NMJ stability and repair. Indeed, muscarinic receptors (mAChR) regulate the repair phenotype of PSCs and are overactivated at disease-resistant NMJs (Soleus muscle) in SOD1G37R mice. However, it remains unknown whether this is the case at disease-vulnerable NMJs and whether it translates into an impairment of PSC-dependent repair mechanisms. We used Soleus and Sternomastoid muscles from SOD1G37R mice and performed Ca2+-imaging to monitor PSC activity and used immunohistochemistry to analyze their repair and phagocytic properties. We show that PSC mAChR-dependent activity was transiently increased at disease-vulnerable NMJs (Sternomastoid muscle). Furthermore, PSCs from both muscles extended disorganized processes from denervated NMJs and failed to initiate or guide nerve terminal sprouts at disease-vulnerable NMJs, a phenomenon essential for compensatory reinnervation. This was accompanied by a failure of numerous PSCs to upregulate Galectin-3 (MAC-2), a marker of glial axonal debris phagocytosis, upon NMJ denervation in SOD1 mice. Finally, differences in these PSC-dependent NMJ repair mechanisms were MU-type dependent, thus reflecting MU vulnerability in ALS. Together, these results reveal that neuron-glia communication is ubiquitously altered at the NMJ in ALS. This appears to prevent PSCs from adopting a repair phenotype, resulting in a maladapted response to denervation at the NMJ in ALS.SIGNIFICANCE STATEMENTUnderstanding how the complex interplay between neurons and glial cells ultimately lead to the degeneration of motor neurons and loss of motor function is a fundamental question to comprehend amyotrophic lateral sclerosis. An early and persistent alteration of glial cell activity takes place at the neuromuscular junction (NMJ), the output of motor neurons, but its impact on NMJ repair remains unknown. Here, we reveal that glial cells at disease-vulnerable NMJs often fail to guide compensatory nerve terminal sprouts and to adopt a phagocytic phenotype on denervated NMJs in SOD1G37R mice. These results show that glial cells at the NMJ elaborate an inappropriate response to NMJ degeneration in a manner that reflects motor-unit vulnerability and potentially impairs compensatory reinnervation.

Mechanisms Regulating Neuromuscular Junction Development and Function and Causes of Muscle Wasting

2015 ◽  
Vol 95 (3) ◽  
pp. 809-852 ◽  
Author(s):  
Lionel A. Tintignac ◽  
Hans-Rudolf Brenner ◽  
Markus A. Rüegg
Keyword(s):  
Neuromuscular Junction ◽  
Muscle Mass ◽  
Motor Neurons ◽  
Structural Changes ◽  
Muscle Wasting ◽  
Chemical Synapse ◽  
Neuromuscular Activity ◽  
Medical Need ◽  
Metabolic Properties ◽  
And Function

The neuromuscular junction is the chemical synapse between motor neurons and skeletal muscle fibers. It is designed to reliably convert the action potential from the presynaptic motor neuron into the contraction of the postsynaptic muscle fiber. Diseases that affect the neuromuscular junction may cause failure of this conversion and result in loss of ambulation and respiration. The loss of motor input also causes muscle wasting as muscle mass is constantly adapted to contractile needs by the balancing of protein synthesis and protein degradation. Finally, neuromuscular activity and muscle mass have a major impact on metabolic properties of the organisms. This review discusses the mechanisms involved in the development and maintenance of the neuromuscular junction, the consequences of and the mechanisms involved in its dysfunction, and its role in maintaining muscle mass during aging. As life expectancy is increasing, loss of muscle mass during aging, called sarcopenia, has emerged as a field of high medical need. Interestingly, aging is also accompanied by structural changes at the neuromuscular junction, suggesting that the mechanisms involved in neuromuscular junction maintenance might be disturbed during aging. In addition, there is now evidence that behavioral paradigms and signaling pathways that are involved in longevity also affect neuromuscular junction stability and sarcopenia.

scholarly journals HumanAPPGene Expression Alters Active Zone Distribution and Spontaneous Neurotransmitter Release at theDrosophilaLarval Neuromuscular Junction

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Ekaterina A. Saburova ◽  
Alexander N. Vasiliev ◽  
Violetta V. Kravtsova ◽  
Elena V. Ryabova ◽  
Andrey L. Zefirov ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Motor Neurons ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Molecular Mechanisms ◽  
Neuromuscular Junctions ◽  
Functional Organization ◽  
Functional Changes ◽  
Human Genes ◽  
Active Zones

This study provides further insight into the molecular mechanisms that control neurotransmitter release. Experiments were performed on larval neuromuscular junctions of transgenicDrosophila melanogasterlines with different levels of human amyloid precursor protein (APP) production. To express human genes in motor neurons ofDrosophila, the UAS-GAL4 system was used. HumanAPPgene expression increased the number of synaptic boutons per neuromuscular junction. The total number of active zones, detected by Bruchpilot protein puncta distribution, remained unchanged; however, the average number of active zones per bouton decreased. These disturbances were accompanied by a decrease in frequency of miniature excitatory junction potentials without alteration in random nature of spontaneous quantal release. Similar structural and functional changes were observed with co-overexpression of humanAPPandβ-secretasegenes. InDrosophilaline with expression of human amyloid-β42 peptide itself, parameters analyzed did not differ from controls, suggesting the specificity of APP effects. These results confirm the involvement of APP in synaptogenesis and provide evidence to suggest that humanAPPoverexpression specifically disturbs the structural and functional organization of active zone and results in altered Bruchpilot distribution and lowered probability of spontaneous neurotransmitter release.

scholarly journals GAL4 drivers specific for Type Ib and Type Is motor neurons in Drosophila

2018 ◽  
Author(s):  
Juan J. Perez-Moreno ◽  
Cahir J. O’Kane
Keyword(s):  
Neuromuscular Junction ◽  
Motor Neurons ◽  
Cell Biology ◽  
Neuronal Cell ◽  
Model System ◽  
High Expression ◽  
Neuromuscular System ◽  
Type I ◽  
Physiological Properties ◽  
Synaptic Level

ABSTRACTThe Drosophila larval neuromuscular system is extensively used by researchers to study neuronal cell biology, and Drosophila glutamatergic motor neurons (MNs) have become a major model system. There are two main Types of glutamatergic MNs, Ib and Is, with different structural and physiological properties at synaptic level at the neuromuscular junction. To generate genetic tools to identify and manipulate MNs of each Type, we screened for GAL4 driver lines for this purpose. Here we describe GAL4 drivers specific for examples of neurons within each Type, Ib or Is. These drivers showed high expression levels and were expressed in only few MNs, making them amenable tools for specific studies of both axonal and synapse biology in identified Type I MNs.

scholarly journals The Vesicular Acetylcholine Transporter Is Required for Neuromuscular Development and Function

2009 ◽  
Vol 29 (19) ◽  
pp. 5238-5250 ◽  
Author(s):  
Braulio M. de Castro ◽  
Xavier De Jaeger ◽  
Cristina Martins-Silva ◽  
Ricardo D. F. Lima ◽  
Ernani Amaral ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Motor Neurons ◽  
Choline Acetyltransferase ◽  
Knockout Mice ◽  
Synaptic Vesicles ◽  
Electrophysiological Recordings ◽  
Physiological Relevance ◽  
And Function ◽  
Neuromuscular Development ◽  
High Affinity Choline Transporter

ABSTRACT The vesicular acetylcholine (ACh) transporter (VAChT) mediates ACh storage by synaptic vesicles. However, the VAChT-independent release of ACh is believed to be important during development. Here we generated VAChT knockout mice and tested the physiological relevance of the VAChT-independent release of ACh. Homozygous VAChT knockout mice died shortly after birth, indicating that VAChT-mediated storage of ACh is essential for life. Indeed, synaptosomes obtained from brains of homozygous knockouts were incapable of releasing ACh in response to depolarization. Surprisingly, electrophysiological recordings at the skeletal-neuromuscular junction show that VAChT knockout mice present spontaneous miniature end-plate potentials with reduced amplitude and frequency, which are likely the result of a passive transport of ACh into synaptic vesicles. Interestingly, VAChT knockouts exhibit substantial increases in amounts of choline acetyltransferase, high-affinity choline transporter, and ACh. However, the development of the neuromuscular junction in these mice is severely affected. Mutant VAChT mice show increases in motoneuron and nerve terminal numbers. End plates are large, nerves exhibit abnormal sprouting, and muscle is necrotic. The abnormalities are similar to those of mice that cannot synthesize ACh due to a lack of choline acetyltransferase. Our results indicate that VAChT is essential to the normal development of motor neurons and the release of ACh.

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