scholarly journals Lrig1 and Lrig3 cooperate to control Ret receptor signaling, sensory axonal growth and epidermal innervation

Development ◽  
2021 ◽  
Author(s):  
Ana Paula De Vincenti ◽  
Fernando C. Alsina ◽  
Facundo Ferrero Restelli ◽  
Håkan Hedman ◽  
Fernanda Ledda ◽  
...  

Negative feedback-loop represents a regulatory mechanism that guarantees signaling thresholds compatible with a physiological response. Previously, we established that Lrig1, acts through this mechanism to inhibit Ret activity. However, it is unclear whether other Lrig-family members play similar roles. Here, we show that Lrig1 and Lrig3 are co-expressed in Ret-positive dorsal root ganglion (DRG) neurons. Lrig3, like Lrig1, interacts with Ret and inhibits GDNF/Ret signaling. Treatment of DRG neurons with GDNF ligands induces a significant increase in the expression of Lrig1 and Lrig3. Our findings show that whereas single deletion of either Lrig1 or Lrig3 fails to promote Ret-mediated axonal growth, haploinsufficiency of Lrig1 in Lrig3 mutants significantly potentiates Ret signaling and axonal growth of DRG neurons in response to GDNF ligands. We observe that Lrig1 and Lrig3 act redundantly to ensure proper cutaneous innervation of nonpeptidergic axons and behavioral sensitivity to cold, which correlate with a significant increase in the expression of the cold-responsive channel, TrpA1. Together our findings provide novel insights into the in vivo functions through which Lrig genes control morphology, connectivity and function in sensory neurons.

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1607 ◽  
Author(s):  
Manikowski ◽  
Jakobs ◽  
Jboor ◽  
Grobe

Sonic hedgehog (Shh) signaling plays a tumor-promoting role in many epithelial cancers. Cancer cells produce soluble a Shh that signals to distant stromal cells that express the receptor Patched (Ptc). These receiving cells respond by producing other soluble factors that promote cancer cell growth, generating a positive feedback loop. To interfere with reinforced Shh signaling, we examined the potential of defined heparin and heparan sulfate (HS) polysaccharides to block Shh solubilization and Ptc receptor binding. We confirm in vitro and in vivo that proteolytic cleavage of the N-terminal Cardin–Weintraub (CW) amino acid motif is a prerequisite for Shh solubilization and function. Consistent with the established binding of soluble heparin or HS to the Shh CW target motif, both polysaccharides impaired proteolytic Shh processing and release from source cells. We also show that HS and heparin bind to, and block, another set of basic amino acids required for unimpaired Shh binding to Ptc receptors on receiving cells. Both modes of Shh activity downregulation depend more on HS size and overall charge than on specific HS sulfation modifications. We conclude that heparin oligosaccharide interference in the physiological roles of HS in Shh release and reception may be used to expand the field of investigation to pharmaceutical intervention of tumor-promoting Shh functions.


1998 ◽  
Vol 79 (5) ◽  
pp. 2668-2676 ◽  
Author(s):  
S. D. Dib-Hajj ◽  
J. A. Black ◽  
T. R. Cummins ◽  
A. M. Kenney ◽  
J. D. Kocsis ◽  
...  

Dib-Hajj, S. D., J. A. Black, T. R. Cummins, A. M. Kenney, J. D. Kocsis, and S. G. Waxman. Rescue of α-SNS sodium channel expression in small dorsal root ganglion neurons after axotomy by nerve growth factor in vivo. J. Neurophysiol. 79: 2668–2676, 1998. Small (18–25 μm diam) dorsal root ganglion (DRG) neurons are known to express high levels of tetrodotoxin-resistant (TTX-R) sodium current and the mRNA for the α-SNS sodium channel, which encodes a TTX-R channel when expressed in oocytes. These neurons also preferentially express the high affinity receptor for nerve growth factor (NGF), TrkA. Levels of TTX-R sodium current and of α-SNS mRNA are reduced in these cells after axotomy. To determine whether NGF participates in the regulation of TTX-R current and α-SNS mRNA in small DRG neurons in vivo, we axotomized small lumbar DRG neurons by sciatic nerve transection and administered NGF or Ringer solution to the proximal nerve stump using osmotic pumps. Ten to 12 days after pump implant, whole cell patch-clamp recording demonstrated that TTX-R current density was decreased in Ringer-treated axotomized neurons (154 ± 45 pA/pF; mean ± SE) compared with nonaxotomized control neurons (865 ± 123 pA/pF) and was restored partially toward control levels in NGF-treated axotomized neurons (465 ± 78 pA/pF). The V 1/2 for steady-state activation and inactivation of TTX-R currents were similar in control, Ringer- and NGF-treated axotomized neurons. Reverse transcription polymerase chain reaction revealed an upregulation of α-SNS mRNA levels in NGF-treated compared with Ringer-treated axotomized DRG. In situ hybridization showed that α-SNS mRNA levels were decreased significantly in small Ringer-treated axotomized DRG neurons in vivo and also in small DRG neurons that were dissociated and maintained in vitro, so as to correspond to the patch-clamp conditions. NGF-treated axotomized neurons had a significant increase in α-SNS mRNA expression, compared with Ringer-treated axotomized cells. These results show that the administration of exogenous NGF in vivo, to the proximal nerve stump of the transected sciatic nerve, results in an upregulation of TTX-R sodium current and of α-SNS mRNA levels in small DRG neurons. Retrogradely transported NGF thus appears to participate in the control of excitability in these cells via actions that include the regulation of sodium channel gene expression in vivo.


2003 ◽  
Vol 89 (3) ◽  
pp. 1588-1602 ◽  
Author(s):  
Chao Ma ◽  
Yousheng Shu ◽  
Zheng Zheng ◽  
Yong Chen ◽  
Hang Yao ◽  
...  

We investigated electrophysiological changes in chronically axotomized and neighboring intact dorsal root ganglion (DRG) neurons in rats after either a peripheral axotomy consisting of an L5 spinal nerve ligation (SNL) or a central axotomy produced by an L5 partial rhizotomy (PR). SNL produced lasting hyperalgesia to punctate indentation and tactile allodynia to innocuous stroking of the foot ipsilateral to the injury. PR produced ipsilateral hyperalgesia without allodynia with recovery by day 10. Intracellular recordings were obtained in vivo from the cell bodies (somata) of axotomized and intact DRG neurons, some with functionally identified peripheral receptive fields. PR produced only minor electrophysiological changes in both axotomized and intact somata in L5 DRG. In contrast, extensive changes were observed after SNL in large- and medium-sized, but not small-sized, somata of intact (L4) as well as axotomized (L5) DRG neurons. These changes included (in relation to sham values) higher input resistance, lower current and voltage thresholds, and action potentials with longer durations and slower rising and falling rates. The incidence of spontaneous activity, recorded extracellularly from dorsal root fibers in vitro, was significantly higher (in relation to sham) after SNL but not after PR, and occurred in myelinated but not unmyelinated fibers from both L4 (9.1%) and L5 (16.7%) DRGs. We hypothesize that the changes in the electrophysiological properties of axotomized and intact DRG neurons after SNL are produced by a mechanism associated with Wallerian degeneration and that the hyperexcitability of intact neurons may contribute to SNL-induced hyperalgesia and allodynia.


Endocrinology ◽  
2008 ◽  
Vol 149 (7) ◽  
pp. 3452-3460 ◽  
Author(s):  
Anuradha Chakrabarty ◽  
Audrey Blacklock ◽  
Stanislav Svojanovsky ◽  
Peter G. Smith

Many painful conditions occur more frequently in women, and estrogen is a predisposing factor. Estrogen may contribute to some pain syndromes by enhancing axon outgrowth by sensory dorsal root ganglion (DRG) neurons. The objective of the present study was to define mechanisms by which estrogen elicits axon sprouting. The estrogen receptor-α agonist propyl pyrazole triol induced neurite outgrowth from cultured neonatal DRG neurons, whereas the estrogen receptor-β agonist diarylpropionitrile was ineffective. 17β-Estradiol (E2) elicited sprouting from peripherin-positive unmyelinated neurons, but not larger NF200-positive myelinated neurons. Microarray analysis showed that E2 up-regulates angiotensin II (ANGII) receptor type 2 (AT2) mRNA in vitro, and studies in adult rats confirmed increased DRG mRNA and protein in vivo. AT2 plays a central role in E2-induced axon sprouting because AT2 blockade by PD123,319 eliminated estrogen-mediated sprouting in vitro. We assessed whether AT2 may be responding to locally synthesized ANGII. DRG from adult rats expressed mRNA for renin, angiotensinogen, and angiotensin converting enzyme (ACE), and protein products were present and occasionally colocalized within neurons and other DRG cells. We determined if locally synthesized ANGII plays a role in estrogen-mediated sprouting by blocking its formation using the ACE inhibitor enalapril. ACE inhibition prevented estrogen-induced neuritogenesis. These findings support the hypothesis that estrogen promotes DRG nociceptor axon sprouting by up-regulating the AT2 receptor, and that locally synthesized ANGII can induce axon formation. Therefore, estrogen may contribute to some pain syndromes by enhancing the pro-neuritogenic effects of AT2 activation by ANGII.


Author(s):  
Kristina Rodionova ◽  
Karl F. Hilgers ◽  
Salman Rafii-Tabrizi ◽  
Johannes Doellner ◽  
Nada Cordasic ◽  
...  

AbstractPrevious data suggest that renal afferent nerve activity is increased in hypertension exerting sympathoexcitatory effects. Hence, we wanted to test the hypothesis that in renovascular hypertension, the activity of dorsal root ganglion (DRG) neurons with afferent projections from the kidneys is augmented depending on the degree of intrarenal inflammation. For comparison, a nonhypertensive model of mesangioproliferative nephritis was investigated. Renovascular hypertension (2-kidney, 1-clip [2K1C]) was induced by unilateral clipping of the left renal artery and mesangioproliferative glomerulonephritis (anti-Thy1.1) by IV injection of a 1.75-mg/kg BW OX-7 antibody. Neuronal labeling (dicarbocyanine dye [DiI]) in all rats allowed identification of renal afferent dorsal root ganglion (DRG) neurons. A current clamp was used to characterize neurons as tonic (sustained action potential [AP] firing) or phasic (1–4 AP) upon stimulation by current injection. All kidneys were investigated using standard morphological techniques. DRG neurons exhibited less often tonic response if in vivo axonal input from clipped kidneys was received (30.4% vs. 61.2% control, p < 0.05). However, if the nerves to the left clipped kidneys were cut 7 days prior to investigation, the number of tonic renal neurons completely recovered to well above control levels. Interestingly, electrophysiological properties of neurons that had in vivo axons from the right non-clipped kidneys were not distinguishable from controls. Renal DRG neurons from nephritic rats also showed less often tonic activity upon current injection (43.4% vs. 64.8% control, p < 0.05). Putative sympathoexcitatory and impaired sympathoinhibitory renal afferent nerve fibers probably contribute to increased sympathetic activity in 2K1C hypertension.


2019 ◽  
Author(s):  
Paolo La Montanara ◽  
Arnau Hervera ◽  
Lucas Baltussen ◽  
Thomas Hutson ◽  
Ilaria Palmisano ◽  
...  

AbstractCyclin-dependent-like kinase 5 (Cdkl5) gene mutations lead to an X-linked disorder that is characterized by infantile epileptic encephalopathy, developmental delay and hypotonia. However, we found that a substantial percentage of these patients also report a previously unrecognised anamnestic deficiency in pain perception. Consistent with a role in nociception, we discovered that Cdkl5 is expressed selectively in nociceptive dorsal root ganglia (DRG) neurons in mice and in iPS-derived human nociceptors. CDKL5 deficient mice display defective epidermal innervation and conditional deletion of Cdkl5 in DRG sensory neurons significantly impairs nociception, phenocopying CDKL5 deficiency disorder in patients. Mechanistically, Cdkl5 interacts with CaMKIIα to control outgrowth as well as TRPV1-dependent signalling, which are disrupted in both Cdkl5 mutant murine DRG and human iPS-derived nociceptors. Together, these findings unveil a previously unrecognized role for Cdkl5 in nociception, proposing an original regulatory mechanism for pain perception with implications for future therapeutics in CDKL5 deficiency disorder.One Sentence SummaryCyclin-dependent-like kinase 5 (Cdkl5) controls nociception in patients and murine models of Cdkl5 deficiency disorder via CaMKII-dependent mechanisms


2020 ◽  
Author(s):  
Sampurna Chakrabarti ◽  
Luke A. Pattison ◽  
Balint Doleschall ◽  
Rebecca H. Rickman ◽  
Helen Blake ◽  
...  

AbstractObjectiveJoint pain is the major clinical symptom of arthritis that affects millions of people. Controlling the excitability of knee-innervating dorsal root ganglion (DRG) neurons (knee neurons) could potentially provide pain relief. Therefore, our objective was to evaluate whether the newly engineered adeno-associated virus (AAV) serotype, AAV-PHP.S, can deliver functional artificial receptors to control knee neuron excitability following intra-articular knee injection.MethodsAAV-PHP.S virus packaged with dTomato fluorescent protein and either excitatory (Gq) or inhibitory (Gi) designer receptors activated by designer drugs (DREADDs) was injected into the knee joint of adult mice. Labelling of DRG neurons by AAV-PHP.S from the knee was evaluated using immunohistochemistry. Functionality of Gq- and Gi-DREADDs was evaluated using whole-cell patch clamp electrophysiology on acutely cultured DRG neurons. Pain behavior in mice was assessed using a digging assay, dynamic weight bearing and rotarod, before and after intra-peritoneal administration of the DREADD activator, Compound 21.ResultsWe show that AAV-PHP.S can deliver functional genes into the DRG neurons when injected into the knee joint in a similar manner to the well-established retrograde tracer, fast blue. Short-term activation of AAV-PHP.S delivered Gq-DREADD increases excitability of knee neurons in vitro, without inducing overt pain in mice when activated in vivo. By contrast, in vivo Gi-DREADD activation alleviated complete Freund’s adjuvant mediated knee inflammation-induced deficits in digging behavior, with a concomitant decrease in knee neuron excitability observed in vitro.ConclusionsWe describe an AAV-mediated chemogenetic approach to specifically control joint pain, which may be utilized in translational arthritic pain research.


2020 ◽  
Author(s):  
Tao Wang ◽  
Jin Tao ◽  
Yehong Fang ◽  
Chao Ma

Abstract Background: Chronic pruritus is a symptom that commonly observed in neurological diseases. It has been hypothesized that the chronic pruritus may result from sensitization of itch-signaling pathways but the mechanisms remain obscure.Methods: In this study, we established a mouse model of chronic compression of dorsal root ganglion (CCD) and injected various pruritogenic and algogenic agents intradermally to the calf skin ipsilateral to the compressed DRG. We additionally investigated if pruritogen-evoked activities of dorsal root ganglion (DRG) neurons is enhanced in this model. The expression of TRPV1, CGRP and H1R was detected with immunoflorescent staining. DRG neurons response to four agents using in vivo calcium imaging.Results: Compared to the naïve mice, a significant increase in itch-related behaviors was observed in the CCD mice after the injection of pruritogens including histamine and BAM8-22, but not after the injection of algogenic agents including capsaicine and 5-HT, although all the above agents evoked enhanced pain-related behaviors toward the injected site. In vivo calcium imaging revealed that compressed DRG neurons exhibited significantly enhanced responses to histamine and BAM8-22. Immunoflorescent staining also showed that the histamine receptor H1 and the capsaicin receptor TRPV1 were significantly upregulated in DRG neurons.Conclusions: Our findings indicated that sensitization of primary pruriceptive neurons may underlie the enhanced itch sensation after chronic compression of DRG neurons in mice, and may play a role in chronic pruritus in neurological diseases.


2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Di Wu ◽  
Ying Jin ◽  
Tatiana M. Shapiro ◽  
Abhishek Hinduja ◽  
Peter W. Baas ◽  
...  

AbstractAfter a dorsal root crush injury, centrally-projecting sensory axons fail to regenerate across the dorsal root entry zone (DREZ) to extend into the spinal cord. We find that chemogenetic activation of adult dorsal root ganglion (DRG) neurons improves axon growth on an in vitro model of the inhibitory environment after injury. Moreover, repeated bouts of daily chemogenetic activation of adult DRG neurons for 12 weeks post-crush in vivo enhances axon regeneration across a chondroitinase-digested DREZ into spinal gray matter, where the regenerating axons form functional synapses and mediate behavioral recovery in a sensorimotor task. Neuronal activation-mediated axon extension is dependent upon changes in the status of tubulin post-translational modifications indicative of highly dynamic microtubules (as opposed to stable microtubules) within the distal axon, illuminating a novel mechanism underlying stimulation-mediated axon growth. We have identified an effective combinatory strategy to promote functionally-relevant axon regeneration of adult neurons into the CNS after injury.


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