c-Jun NH2-terminal Kinase (JNK)-interacting Protein-3 (JIP3) Regulates Neuronal Axon Elongation in a Kinesin- and JNK-dependent Manner

The development of neuronal polarity is essential for the establishment of the accurate patterning of neuronal circuits in the brain. However, little is known about the underlying molecular mechanisms that control rapid axon elongation during neuronal development. Here, we report that c-Jun NH2-terminal kinase (JNK)-interacting protein-3 (JIP3) is highly expressed at axon tips during the critical period for axon development. Using gain- and loss-of-function approaches, immunofluorescence analysis, and in utero electroporation, we find that JIP3 can enhance axon elongation in primary hippocampal neurons and cortical neurons in vivo. We further demonstrate that JIP3 promotes axon elongation in a kinesin- and JNK-dependent manner using several deletion mutants of JIP3. Next, we demonstrate that the successful transportation of JIP3 to axon tips by kinesin is a prerequisite for enhancing JNK phosphorylation in this area and therefore promotes axon elongation, constituting a novel mechanism for coupling JIP3 anterograde transport with JNK signaling at the distal axons and axon elongation. Finally, our immunofluorescence data suggest that the activation of JNK at axon tips facilitates axon elongation by modulating cofilin activity and actin filament dynamics. These findings may have important implications for our understanding of neuronal axon elongation during development.

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Nogo-A Modulates the Synaptic Excitation of Hippocampal Neurons in a Ca2+-Dependent Manner

Cells ◽

10.3390/cells10092299 ◽

2021 ◽

Vol 10 (9) ◽

pp. 2299

Author(s):

Kristin Metzdorf ◽

Steffen Fricke ◽

Maria Teresa Balia ◽

Martin Korte ◽

Marta Zagrebelsky

Keyword(s):

Synaptic Plasticity ◽

Hippocampal Neurons ◽

Molecular Mechanisms ◽

Growth Inhibitor ◽

Neurite Growth ◽

Excitatory Synapses ◽

Dependent Manner ◽

Loss Of Function ◽

Synaptic Excitation ◽

Primary Mouse

A tight regulation of the balance between inhibitory and excitatory synaptic transmission is a prerequisite for synaptic plasticity in neuronal networks. In this context, the neurite growth inhibitor membrane protein Nogo-A modulates synaptic plasticity, strength, and neurotransmitter receptor dynamics. However, the molecular mechanisms underlying these actions are unknown. We show that Nogo-A loss-of-function in primary mouse hippocampal cultures by application of a function-blocking antibody leads to higher excitation following a decrease in GABAARs at inhibitory and an increase in the GluA1, but not GluA2 AMPAR subunit at excitatory synapses. This unbalanced regulation of AMPAR subunits results in the incorporation of Ca2+-permeable GluA2-lacking AMPARs and increased intracellular Ca2+ levels due to a higher Ca2+ influx without affecting its release from the internal stores. Increased neuronal activation upon Nogo-A loss-of-function prompts the phosphorylation of the transcription factor CREB and the expression of c-Fos. These results contribute to the understanding of the molecular mechanisms underlying the regulation of the excitation/inhibition balance and thereby of plasticity in the brain.

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Cylindromatosis Drives Synapse Pruning and Weakening by Promoting Macroautophagy through Akt-mTOR Signaling

10.1101/2021.12.08.471792 ◽

2021 ◽

Author(s):

Wei-Dong Yao ◽

Alexis S Zajicek ◽

Huihui Dai ◽

Mary Catherine Skolfield ◽

Hannah L Phillips ◽

...

Keyword(s):

Molecular Mechanisms ◽

Mtor Signaling ◽

Mammalian Brain ◽

Autophagic Flux ◽

Dependent Manner ◽

Synapse Elimination ◽

Loss Of Function ◽

Synapse Maintenance ◽

Behavioral Impairments

The lysine-63 deubiquitinase cylindromatosis (CYLD) is long recognized as a tumor suppressor in immunity and inflammation and its loss-of-function mutations lead to familial cylindromatosis. However, recent studies reveal that CYLD is enriched in mammalian brain postsynaptic densities, and a gain-of-function mutation causes frontotemporal dementia (FTD), suggesting critical roles at excitatory synapses. Here we report that CYLD drives synapse elimination and weakening by acting on the Akt-mTOR-autophagy axis. Mice lacking CYLD display abnormal sociability, anxiety- and depression-like behaviors, and cognitive inflexibility. These behavioral impairments are accompanied by excessive synapse numbers, increased postsynaptic efficacy, augmented synaptic summation, and impaired NMDA receptor-dependent hippocampal long-term depression (LTD). Exogenous expression of CYLD results in removal of established dendritic spines from mature neurons in a deubiquitinase activity-dependent manner. In search of underlying molecular mechanisms, we find that CYLD knockout mice display marked overactivation of Akt and mTOR and reduced autophagic flux and, conversely, CYLD overexpression potently suppresses Akt and mTOR activity and promotes autophagy. Consequently, abrogating the Akt-mTOR-autophagy signaling pathway abolishes CYLD-induced spine loss, whereas enhancing autophagy in vivo by the mTOR inhibitor rapamycin rescues the synaptic pruning and LTD deficits in mutant mice. Our findings establish CYLD, via Akt-mTOR signaling, as a synaptic autophagy activator that exerts critical modulations on synapse maintenance, function, and plasticity.

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A specific Ret receptor isoform is required for pioneer axon outgrowth and growth cone dynamics

10.1101/424432 ◽

2018 ◽

Author(s):

Adam M. Tuttle ◽

Catherine M. Drerup ◽

Molly H. Marra ◽

Alex V. Nechiporuk

Keyword(s):

Growth Cone ◽

Axon Growth ◽

Retrograde Transport ◽

Growth Cones ◽

Axon Outgrowth ◽

Loss Of Function ◽

Anterograde Transport ◽

Interacting Protein ◽

Pioneer Neurons

AbstractIn many cases, axon growth and guidance are driven by pioneer axons, the first axons to grow in a particular region. Despite their dynamic pathfinding capabilities and developmental importance, there are very few pioneer neuron specific markers and thus their in vivo identification and functional interrogation have been difficult. We found that a Ret receptor isoform, Ret51, is highly enriched in peripheral sensory pioneer neurons and is required for pioneer axon outgrowth. Ret null mutant pioneer neurons differentiate normally; however, they displayed defects in growth cone morphology and formation of filopodia before pioneer axon extension prematurely halts. We also demonstrate loss-of-function of a retrograde cargo adaptor, JNK-interacting protein 3 (Jip3), phenocopied many of these axonal defects. We further found that loss of Jip3 led to accumulation of activated Ret receptor in pioneer growth cones, indicating a failure in the clearance of activated Ret from growth cones. Using an axon sever approach as well as in vivo analysis of axonal transport, we showed Jip3 specifically mediates retrograde, but not anterograde, transport of activated Ret51. Finally, live imaging revealed that Jip3 and Ret51 were retrogradely co-transported in pioneer axons, suggesting Jip3 functions as an adapter for retrograde transport of Ret51. Taken together, these results identify Ret51 as a molecular marker of pioneer neurons and elucidate an important isoform-specific role for Ret51 in axon growth and growth cone dynamics during development.

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Phosphorylation of CRMP2 by Cdk5 Regulates Dendritic Spine Development of Cortical Neuron in the Mouse Hippocampus

Neural Plasticity ◽

10.1155/2016/6790743 ◽

2016 ◽

Vol 2016 ◽

pp. 1-7 ◽

Cited By ~ 19

Author(s):

Xiaohua Jin ◽

Kodai Sasamoto ◽

Jun Nagai ◽

Yuki Yamazaki ◽

Kenta Saito ◽

...

Keyword(s):

Mouse Brain ◽

Dendritic Spines ◽

Dendritic Spine ◽

Cortical Neurons ◽

Hippocampal Neurons ◽

Molecular Mechanisms ◽

Brain Functions ◽

Spine Development ◽

Mouse Hippocampus

Proper density and morphology of dendritic spines are important for higher brain functions such as learning and memory. However, our knowledge about molecular mechanisms that regulate the　development and maintenance of dendritic spines is limited. We recently reported that cyclin-dependent kinase 5 (Cdk5) is required for the development and maintenance of dendritic spines of cortical neurons in the mouse brain. Previousin vitrostudies have suggested the involvement of Cdk5 substrates in the formation of dendritic spines; however, their role in spine development has not been testedin vivo. Here, we demonstrate that Cdk5 phosphorylates collapsin response mediator protein 2 (CRMP2) in the dendritic spines of cultured hippocampal neurons andin vivoin the mouse brain. When we eliminated CRMP2 phosphorylation inCRMP2KI/KImice, the densities of dendritic spines significantly decreased in hippocampal CA1 pyramidal neurons in the mouse brain. These results indicate that phosphorylation of CRMP2 by Cdk5 is important for dendritic spine development in cortical neurons in the mouse hippocampus.

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Decoding the temporal nature of brain GR activity in the NFκB signal transition leading to depressive-like behavior

Molecular Psychiatry ◽

10.1038/s41380-021-01016-1 ◽

2021 ◽

Author(s):

Young-Min Han ◽

Min Sun Kim ◽

Juyeong Jo ◽

Daiha Shin ◽

Seung-Hae Kwon ◽

...

Keyword(s):

Inhibitory Action ◽

Time Course ◽

Molecular Mechanisms ◽

Late Phase ◽

Fine Tuning ◽

Dependent Manner ◽

Middle Phase ◽

Temporal Shift

AbstractThe fine-tuning of neuroinflammation is crucial for brain homeostasis as well as its immune response. The transcription factor, nuclear factor-κ-B (NFκB) is a key inflammatory player that is antagonized via anti-inflammatory actions exerted by the glucocorticoid receptor (GR). However, technical limitations have restricted our understanding of how GR is involved in the dynamics of NFκB in vivo. In this study, we used an improved lentiviral-based reporter to elucidate the time course of NFκB and GR activities during behavioral changes from sickness to depression induced by a systemic lipopolysaccharide challenge. The trajectory of NFκB activity established a behavioral basis for the NFκB signal transition involved in three phases, sickness-early-phase, normal-middle-phase, and depressive-like-late-phase. The temporal shift in brain GR activity was differentially involved in the transition of NFκB signals during the normal and depressive-like phases. The middle-phase GR effectively inhibited NFκB in a glucocorticoid-dependent manner, but the late-phase GR had no inhibitory action. Furthermore, we revealed the cryptic role of basal GR activity in the early NFκB signal transition, as evidenced by the fact that blocking GR activity with RU486 led to early depressive-like episodes through the emergence of the brain NFκB activity. These results highlight the inhibitory action of GR on NFκB by the basal and activated hypothalamic-pituitary-adrenal (HPA)-axis during body-to-brain inflammatory spread, providing clues about molecular mechanisms underlying systemic inflammation caused by such as COVID-19 infection, leading to depression.

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Neuron-specific activation of necroptosis signaling in multiple sclerosis cortical grey matter

Acta Neuropathologica ◽

10.1007/s00401-021-02274-7 ◽

2021 ◽

Vol 141 (4) ◽

pp. 585-604 ◽

Cited By ~ 1

Author(s):

Carmen Picon ◽

Anusha Jayaraman ◽

Rachel James ◽

Catriona Beck ◽

Patricia Gallego ◽

...

Keyword(s):

Multiple Sclerosis ◽

Signaling Pathway ◽

Cortical Neurons ◽

Grey Matter ◽

Molecular Mechanisms ◽

Fold Increase ◽

Cell Types ◽

Meningeal Inflammation ◽

Cortical Grey Matter

AbstractSustained exposure to pro-inflammatory cytokines in the leptomeninges is thought to play a major role in the pathogenetic mechanisms leading to cortical pathology in multiple sclerosis (MS). Although the molecular mechanisms underlying neurodegeneration in the grey matter remain unclear, several lines of evidence suggest a prominent role for tumour necrosis factor (TNF). Using cortical grey matter tissue blocks from post-mortem brains from 28 secondary progressive MS subjects and ten non-neurological controls, we describe an increase in expression of multiple steps in the TNF/TNF receptor 1 signaling pathway leading to necroptosis, including the key proteins TNFR1, FADD, RIPK1, RIPK3 and MLKL. Activation of this pathway was indicated by the phosphorylation of RIPK3 and MLKL and the formation of protein oligomers characteristic of necrosomes. In contrast, caspase-8 dependent apoptotic signaling was decreased. Upregulation of necroptotic signaling occurred predominantly in macroneurons in cortical layers II–III, with little expression in other cell types. The presence of activated necroptotic proteins in neurons was increased in MS cases with prominent meningeal inflammation, with a 30-fold increase in phosphoMLKL+ neurons in layers I–III. The density of phosphoMLKL+ neurons correlated inversely with age at death, age at progression and disease duration. In vivo induction of chronically elevated TNF and INFγ levels in the CSF in a rat model via lentiviral transduction in the meninges, triggered inflammation and neurodegeneration in the underlying cortical grey matter that was associated with increased neuronal expression of TNFR1 and activated necroptotic signaling proteins. Exposure of cultured primary rat cortical neurons to TNF induced necroptosis when apoptosis was inhibited. Our data suggest that neurons in the MS cortex are dying via TNF/TNFR1 stimulated necroptosis rather than apoptosis, possibly initiated in part by chronic meningeal inflammation. Neuronal necroptosis represents a pathogenetic mechanism that is amenable to therapeutic intervention at several points in the signaling pathway.

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Rgs4 is a regulator of mTOR activity required for motoneuron axon outgrowth and neuronal development in zebrafish

Scientific Reports ◽

10.1038/s41598-021-92758-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Aya Mikdache ◽

Marie-José Boueid ◽

Lorijn van der Spek ◽

Emilie Lesport ◽

Brigitte Delespierre ◽

...

Keyword(s):

Nervous System ◽

G Protein ◽

Neural Development ◽

Neuronal Development ◽

Axon Outgrowth ◽

Rgs Proteins ◽

Protein Signaling ◽

Loss Of Function ◽

G Protein Coupled

AbstractThe Regulator of G protein signaling 4 (Rgs4) is a member of the RGS proteins superfamily that modulates the activity of G-protein coupled receptors. It is mainly expressed in the nervous system and is linked to several neuronal signaling pathways; however, its role in neural development in vivo remains inconclusive. Here, we generated and characterized a rgs4 loss of function model (MZrgs4) in zebrafish. MZrgs4 embryos showed motility defects and presented reduced head and eye sizes, reflecting defective motoneurons axon outgrowth and a significant decrease in the number of neurons in the central and peripheral nervous system. Forcing the expression of Rgs4 specifically within motoneurons rescued their early defective outgrowth in MZrgs4 embryos, indicating an autonomous role for Rgs4 in motoneurons. We also analyzed the role of Akt, Erk and mechanistic target of rapamycin (mTOR) signaling cascades and showed a requirement for these pathways in motoneurons axon outgrowth and neuronal development. Drawing on pharmacological and rescue experiments in MZrgs4, we provide evidence that Rgs4 facilitates signaling mediated by Akt, Erk and mTOR in order to drive axon outgrowth in motoneurons and regulate neuronal numbers.

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High Glucose and Lipopolysaccharide Prime NLRP3 Inflammasome via ROS/TXNIP Pathway in Mesangial Cells

Journal of Diabetes Research ◽

10.1155/2016/6973175 ◽

2016 ◽

Vol 2016 ◽

pp. 1-11 ◽

Cited By ~ 48

Author(s):

Hong Feng ◽

Junling Gu ◽

Fang Gou ◽

Wei Huang ◽

Chenlin Gao ◽

...

Keyword(s):

Diabetic Nephropathy ◽

Nlrp3 Inflammasome ◽

High Glucose ◽

Mesangial Cells ◽

Central Component ◽

Dependent Manner ◽

Glomerular Mesangial Cells ◽

Interacting Protein

While inflammation is considered a central component in the development in diabetic nephropathy, the mechanism remains unclear. The NLRP3 inflammasome acts as both a sensor and a regulator of the inflammatory response. The NLRP3 inflammasome responds to exogenous and endogenous danger signals, resulting in cleavage of procaspase-1 and activation of cytokines IL-1β, IL-18, and IL-33, ultimately triggering an inflammatory cascade reaction. This study observed the expression of NLRP3 inflammasome signaling stimulated by high glucose, lipopolysaccharide, and reactive oxygen species (ROS) inhibitor N-acetyl-L-cysteine in glomerular mesangial cells, aiming to elucidate the mechanism by which the NLRP3 inflammasome signaling pathway may contribute to diabetic nephropathy. We found that the expression of thioredoxin-interacting protein (TXNIP), NLRP3, and IL-1βwas observed by immunohistochemistry in vivo. Simultaneously, the mRNA and protein levels of TXNIP, NLRP3, procaspase-1, and IL-1βwere significantly induced by high glucose concentration and lipopolysaccharide in a dose-dependent and time-dependent manner in vitro. This induction by both high glucose and lipopolysaccharide was significantly inhibited by N-acetyl-L-cysteine. Our results firstly reveal that high glucose and lipopolysaccharide activate ROS/TXNIP/ NLRP3/IL-1βinflammasome signaling in glomerular mesangial cells, suggesting a mechanism by which inflammation may contribute to the development of diabetic nephropathy.

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ADP-ribosylation factor–like 4A interacts with Robo1 to promote cell migration by regulating Cdc42 activation

Molecular Biology of the Cell ◽

10.1091/mbc.e18-01-0001 ◽

2019 ◽

Vol 30 (1) ◽

pp. 69-81 ◽

Cited By ~ 2

Author(s):

Tsai-Shin Chiang ◽

Ming-Chieh Lin ◽

Meng-Chen Tsai ◽

Chieh-Hsin Chen ◽

Li-Ting Jang ◽

...

Keyword(s):

Cell Migration ◽

Molecular Mechanisms ◽

Small Gtpase ◽

Dependent Manner ◽

Amino Acid Residues ◽

Adp Ribosylation ◽

Promote Cell Migration ◽

Cytoskeleton Remodeling ◽

Adp Ribosylation Factor

Cell migration is a highly regulated event that is initiated by cell membrane protrusion and actin reorganization. Robo1, a single-pass transmembrane receptor, is crucial for neuronal guidance and cell migration. ADP-ribosylation factor (Arf)–like 4A (Arl4A), an Arf small GTPase, functions in cell morphology, cell migration, and actin cytoskeleton remodeling; however, the molecular mechanisms of Arl4A in cell migration are unclear. Here, we report that the binding of Arl4A to Robo1 modulates cell migration by promoting Cdc42 activation. We found that Arl4A interacts with Robo1 in a GTP-dependent manner and that the Robo1 amino acid residues 1394–1398 are required for this interaction. The Arl4A-Robo1 interaction is essential for Arl4A-induced cell migration and Cdc42 activation but not for the plasma membrane localization of Robo1. In addition, we show that the binding of Arl4A to Robo1 decreases the association of Robo1 with the Cdc42 GTPase-activating protein srGAP1. Furthermore, Slit2/Robo1 binding down-regulates the Arl4A-Robo1 interaction in vivo, thus attenuating Cdc42-mediated cell migration. Therefore, our study reveals a novel mechanism by which Arl4A participates in Slit2/Robo1 signaling to modulate cell motility by regulating Cdc42 activity.

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DIP-2 suppresses ectopic neurite sprouting and axonal regeneration in mature neurons

The Journal of Cell Biology ◽

10.1083/jcb.201804207 ◽

2018 ◽

Vol 218 (1) ◽

pp. 125-133 ◽

Cited By ~ 6

Author(s):

Nathaniel Noblett ◽

Zilu Wu ◽

Zhao Hua Ding ◽

Seungmee Park ◽

Tony Roenspies ◽

...

Keyword(s):

Axonal Regeneration ◽

Neuronal Development ◽

Adult Life ◽

Progressive Increase ◽

Binding Domain ◽

Neuronal Morphology ◽

Loss Of Function ◽

Neuron Morphology ◽

Interacting Protein ◽

Mature Neurons

Neuronal morphology and circuitry established during early development must often be maintained over the entirety of animal lifespans. Compared with neuronal development, the mechanisms that maintain mature neuronal structures and architecture are little understood. The conserved disco-interacting protein 2 (DIP2) consists of a DMAP1-binding domain and two adenylate-forming domains (AFDs). We show that the Caenorhabditis elegans DIP-2 maintains morphology of mature neurons. dip-2 loss-of-function mutants display a progressive increase in ectopic neurite sprouting and branching during late larval and adult life. In adults, dip-2 also inhibits initial stages of axon regeneration cell autonomously and acts in parallel to DLK-1 MAP kinase and EFA-6 pathways. The function of DIP-2 in maintenance of neuron morphology and in axon regrowth requires its AFD domains and is independent of its DMAP1-binding domain. Our findings reveal a new conserved regulator of neuronal morphology maintenance and axon regrowth after injury.

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