Zika Virus Enters Soma of Neuron through NGF/TrkA-Like Endosomal Signaling Pathway

Infection with the Zika virus results in severe neurological disease in adults or congenital Zika syndrome in newborns. We employed the domain search strategy to study the Zika virus glycoprotein E in this work. The results revealed that immature E contains a NGF domain (“MNKCYIQIMDLGHMCDATMSYECPMLDEGVEPDDVDCWCNTTSTWVVYGTCHH”) and is capable of interacting with TrkA. The E/TrkA complex increased E's interaction with receptors such as Axl and facilitated Zika virus endocytosis via clathrin. Rab5 retrograded transmission of Zika virus-containing E/TrkA endosomal signals to neuronal soma. Rab7 helped dissociation of E/TrkA in late acidic endosomes, and then E became mature after the NGF domain was cut. After membrane fusion with the endosome, the Zika virus was released into the neuron cell body. It showed only the immature E protein of Zika had NGF activity. The retrograde trafficking of endosomal signals (E/TrkA) similar to NGF/TrkA enabled Zika virus to infect neuronal cells. E's interference with the TrkA signal impaired neuronal cell growth and results in neuronal cell apoptosis.

Neuroprotection effects of ethyl acetate and n-butanol fractions of the hydroalcoholic extract of Tanacetum bodjnordens on sciatic nerve compression in male rats

Background and Aims: When a neuronal axon is damaged, it returns to the neuron cell body and destroys it. Tanacetum bodjnordens as antioxidant and anti-apoptotic effects. This study aimed to determine the neuroprotective effects of ethyl acetate and n-butanol and hydroalcoholic extracts of Tanacetum bodjnordens on sciatic nerve compression in male rats. Materials and Methods: In this experimental study, 36 male Wistar rats weighing 200-250 g were randomly divided into 6 groups )n=6). In the control group, the right thigh muscle of the rats was split after the anesthetization of the rats, while in the compression and treatment groups, the sciatic nerve was compressed for 60 seconds. The plant extract was injected intraperitoneally on the day of compression and seven days later. After 28 days, samples were taken from the lumbar spinal cord subsequent to performing the perfusion method. Afterward, 7-μm serial sections were prepared and stained using toluidine blue stain after tissue passage. Eventually, the neuronal density of rats in the six groups was compared. Results: Based on the results, the neuronal density in the compression group decreased significantly compared to controls and showed a significant increase in the hydroalcoholic, n-butanol, and aqueous phase treatment groups compared to that in the compression group (P<0.001). Conclusion: According to the results, it seems that Tanacetum bodjnordens leaf extract has neuroprotective effects that promote the regeneration process in damaged neurons and these effects are higher in the aqueous phase fraction.

Crosstalk Between Epithelial Cells, Neurons and Immune Mediators in HSV-1 Skin Infection

Herpes simplex virus type 1 (HSV-1) infection is highly prevalent in humans, with approximately two-thirds of the world population living with this virus. However, only a fraction of those carrying HSV-1, which elicits lifelong infections, are symptomatic. HSV-1 mainly causes lesions in the skin and mucosae but reaches the termini of sensory neurons innervating these tissues and travels in a retrograde manner to the neuron cell body where it establishes persistent infection and remains in a latent state until reactivated by different stimuli. When productive reactivations occur, the virus travels back along axons to the primary infection site, where new rounds of replication are initiated in the skin, in recurrent or secondary infections. During this process, new neuron infections occur. Noteworthy, the mechanisms underlying viral reactivations and the exit of latency are somewhat poorly understood and may be regulated by a crosstalk between the infected neurons and components of the immune system. Here, we review and discuss the immune responses that occur at the skin during primary and recurrent infections by HSV-1, as well as at the interphase of latently-infected neurons. Moreover, we discuss the implications of neuronal signals over the priming and migration of immune cells in the context of HSV-1 infection.

SUN-247 GABA Receptor-Dependent Inhibition and Excitation of GnRH Neuron Dendrons near the Median Eminence in Mice

The gonadotrophin-releasing hormone (GnRH) neuron cell bodies are scattered throughout the basal forebrain but funnel their projections to the median eminence to control fertility in all mammals. In mice, these long projections, termed “dendrons”, have characteristics of both dendrites and axons and are found to receive large numbers of synaptic inputs just prior to entering the median eminence. While the effects of many neurotransmitters have been documented at the GnRH neuron cell body, very little is known about the neural control of the distal dendron. To examine the role of amino acid neurotransmitters in the regulation of the thin GnRH neuron distal dendrons, we used confocal microscopy in combination with real-time GCaMP6 calcium imaging in acute horizontal brain slices. Adult male and female GnRH-Cre mice were given stereotaxic injections of a Cre-dependent AAV expressing GCaMP6s and, &gt; 3 weeks later, the brain removed and a single thick horizontal brain slice prepared that included the base of the brain and median eminence. The intracellular calcium levels of multiple dendrons were monitored simultaneously while puffs of amino acid receptor agonists were applied. Surprisingly, GABA exhibited a dual action on calcium concentrations with an initial transient increase followed by a prolonged decrease and subsequent rebound. The administration of GABAA and GABAB receptor agonist and antagonists revealed that the transient increase resulted from a quickly desensitizing activation of GABAA receptors while the decrease and subsequent rebound was dependent upon the slower kinetics of the GABAB receptor. Kisspeptin exerts a potent long-lasting elevation of calcium levels in GnRH dendrons and this was robustly inhibited by subsequent GABAB receptor activation. In contrast to GABA, glutamate was not found to have any impact on intracellular calcium levels in the distal dendrons and, similarly, the activation of NMDA or AMPA receptors was found to be ineffective. The results show that GABA exerts particularly potent modulatory actions upon basal and evoked calcium concentrations within the GnRH neuron distal dendron. This suggests that acute brief activation of the dendron by GABA would facilitate GnRH release through GABAA receptor activation whereas prolonged GABA release would suppress activity through the GABAB receptor. As such, GABA inputs to the distal dendron appear likely to play a major role in the control of GnRH secretion in the mouse.

Coherent-hybrid STED: a tunable photo-physical pinhole for super-resolution imaging at high contrast

Resolution in microscopy is not limited by diffraction as long as a nonlinear sample response is exploited. In a paradigmatic example, stimulated-emission depletion (STED) fluorescence microscopy fundamentally ‘breaks’ the diffraction limit by using a structured optical pattern to saturate depletion on a previously excited sample area. Two-dimensional (2D) STED, the canonical low-noise STED mode, structures the STED beam by using a vortex phase mask, achieving a significant lateral resolution improvement over confocal fluorescence microscopy. However, axial resolution and optical sectioning remain bound to diffraction. Here we use a tunable coherent-hybrid (CH) beam to improve optical sectioning, markedly reducing background fluorescence. CH-STED, which inherits the 2D-STED immunity to spherical aberration, diversifies the depletion strategy, allowing an optimal balance between two key metrics (lateral resolution and background suppression) to be found. CH-STED is used to perform high-contrast imaging of complex biological structures, such as the mitotic spindle and the neuron cell body.

Diseases of the peripheral nerves

Case History—A 34 yr old man presenting with jaundice, lymphadenopathy, sensory symptoms and muscular weakness. Disorders of peripheral nerve function can be categorized in terms of the site of the primary disturbance. (1) Neuronopathies—conditions that lead to death of the neuron cell body and axon. (2) Axonal neuropathies—conditions that affect axons which may be focal, as in local injury, multifocal, as in vasculitis, or diffuse as in metabolic or toxic disorders often cause selective degeneration of the axons towards the cell bodies (‘dying-back’); (3) Demyelinating neuropathies—conditions in which the myelin sheaths are supporting Schwann cells damaged and the axons are relatively preserved. Combinations of axonal and demyelinating pathology are common. (4) Interstitial neuropathies—conditions in which there is infiltration of the endoneurium for instance by granuloma or amyloid....

Anterograde Spread of Herpes Simplex Virus Type 1 Requires Glycoprotein E and Glycoprotein I but Not Us9

ABSTRACT Anterograde neuronal spread (i.e., spread from the neuron cell body toward the axon terminus) is a critical component of the alphaherpesvirus life cycle. Three viral proteins, gE, gI, and Us9, have been implicated in alphaherpesvirus anterograde spread in several animal models and neuron culture systems. We sought to better define the roles of gE, gI, and Us9 in herpes simplex virus type 1 (HSV-1) anterograde spread using a compartmentalized primary neuron culture system. We found that no anterograde spread occurred in the absence of gE or gI, indicating that these proteins are essential for HSV-1 anterograde spread. However, we did detect anterograde spread in the absence of Us9 using two independent Us9-deleted viruses. We confirmed the Us9 finding in different murine models of neuronal spread. We examined viral transport into the optic nerve and spread to the brain after retinal infection; the production of zosteriform disease after flank inoculation; and viral spread to the spinal cord after flank inoculation. In all models, anterograde spread occurred in the absence of Us9, although in some cases at reduced levels. This finding contrasts with gE- and gI-deleted viruses, which displayed no anterograde spread in any animal model. Thus, gE and gI are essential for HSV-1 anterograde spread, while Us9 is dispensable.

Herpes Simplex Virus gE/gI and US9 Proteins Promote Transport of both Capsids and Virion Glycoproteins in Neuronal Axons

ABSTRACT Following reactivation from latency, alphaherpesviruses replicate in sensory neurons and assemble capsids that are transported in the anterograde direction toward axon termini for spread to epithelial tissues. Two models currently describe this transport. The Separate model suggests that capsids are transported in axons independently from viral envelope glycoproteins. The Married model holds that fully assembled enveloped virions are transported in axons. The herpes simplex virus (HSV) membrane glycoprotein heterodimer gE/gI and the US9 protein are important for virus anterograde spread in the nervous systems of animal models. It was not clear whether gE/gI and US9 contribute to the axonal transport of HSV capsids, the transport of membrane proteins, or both. Here, we report that the efficient axonal transport of HSV requires both gE/gI and US9. The transport of both capsids and glycoproteins was dramatically reduced, especially in more distal regions of axons, with gE−, gI−, and US9-null mutants. An HSV mutant lacking just the gE cytoplasmic (CT) domain displayed an intermediate reduction in capsid and glycoprotein transport. We concluded that HSV gE/gI and US9 promote the separate transport of both capsids and glycoproteins. gE/gI was transported in association with other HSV glycoproteins, gB and gD, but not with capsids. In contrast, US9 colocalized with capsids and not with membrane glycoproteins. Our observations suggest that gE/gI and US9 function in the neuron cell body to promote the loading of capsids and glycoprotein-containing vesicles onto microtubule motors that ferry HSV structural components toward axon tips.

Local Gene Expression in Axons and Nerve Endings: The Glia-Neuron Unit

Neurons have complex and often extensively elongated processes. This unique cell morphology raises the problem of how remote neuronal territories are replenished with proteins. For a long time, axonal and presynaptic proteins were thought to be exclusively synthesized in the cell body, which delivered them to peripheral sites by axoplasmic transport. Despite this early belief, protein has been shown to be synthesized in axons and nerve terminals, substantially alleviating the trophic burden of the perikaryon. This observation raised the question of the cellular origin of the peripheral RNAs involved in protein synthesis. The synthesis of these RNAs was initially attributed to the neuron soma almost by default. However, experimental data and theoretical considerations support the alternative view that axonal and presynaptic RNAs are also transcribed in the flanking glial cells and transferred to the axon domain of mature neurons. Altogether, these data suggest that axons and nerve terminals are served by a distinct gene expression system largely independent of the neuron cell body. Such a local system would allow the neuron periphery to respond promptly to environmental stimuli. This view has the theoretical merit of extending to axons and nerve terminals the marginalized concept of a glial supply of RNA (and protein) to the neuron cell body. Most long-term plastic changes requiring de novo gene expression occur in these domains, notably in presynaptic endings, despite their intrinsic lack of transcriptional capacity. This review enlightens novel perspectives on the biology and pathobiology of the neuron by critically reviewing these issues.