Project description:Acute and chronic trigeminal (TG) neuropathies are the cause of considerable distress, with limited treatments available at present. Nociceptive neurons enriched with the vanilloid type 1 receptor (VR1) partake in pain sensation and sensitization in the TG system. While VR1 blockers with anti-nociceptive potential are of substantial medical interest, their use remains limited due to poor selectivity and lack of cell-targeting capabilities. This study describes a methodology for the alleviation of nociception via targeted depletion of VR1 in TG sensory neurons in rats. In cultured TG ganglion neurons, VR1 expression was virtually abolished by lentiviral short hairpin RNA (LV-VR1). By decorating GFP encoding LV (LV-GFP) and LV-VR1 with IgG192 for targeting TG sensory neurons enriched with the p75 neurotrophin receptor (p75NTR), transduction of a reporter GFP and VR1 depletion was achieved after injection of targeted vectors into the whisker pad. In IgG192/LV-VR1-injected rats, the behavioral response to capsaicin exposure as well as Erk 1/2 phosphorylation and VR1 current activation by capsaicin were significantly reduced. This pioneering investigation, thus, provides a proof of principle for a means of attenuating TG nociception, revealing therapeutic potential.
Project description:Obesity and metabolic syndrome reflect the dysregulation of molecular pathways that control energy homeostasis. Here, we show that the p75 neurotrophin receptor (p75(NTR)) controls energy expenditure in obese mice on a high-fat diet (HFD). Despite no changes in food intake, p75(NTR)-null mice were protected from HFD-induced obesity and remained lean as a result of increased energy expenditure without developing insulin resistance or liver steatosis. p75(NTR) directly interacts with the catalytic subunit of protein kinase A (PKA) and regulates cAMP signaling in adipocytes, leading to decreased lipolysis and thermogenesis. Adipocyte-specific depletion of p75(NTR) or transplantation of p75(NTR)-null white adipose tissue (WAT) into wild-type mice fed a HFD protected against weight gain and insulin resistance. Our results reveal that signaling from p75(NTR) to cAMP/PKA regulates energy balance and suggest that non-CNS neurotrophin receptor signaling could be a target for treating obesity and the metabolic syndrome.
Project description:A member of the TNF receptor family, the p75 neurotrophin receptor (p75(NTR)) has been previously shown to play a role in the regulation of fibrin deposition in the lung. However, the role of p75(NTR) in the regulation of pulmonary vascular tone in the lung is unknown. In the present study, we evaluated the expression of p75(NTR) in mouse pulmonary arteries and the putative role of p75(NTR) in modulating pulmonary vascular tone and agonist responsiveness using wild-type (WT) and p75(NTR) knockout (p75(-/-)) mice. Our data indicated that p75(NTR) is expressed in both smooth muscle and endothelial cells within the pulmonary vascular wall in WT mice. Pulmonary artery rings from p75(-/-) mice exhibited significantly elevated active tension due to endothelin-1-mediated Ca(2+) influx. Furthermore, the contraction due to capacitative Ca(2+) entry (CCE) in response to phenylephrine-mediated active depletion of intracellular Ca(2+) stores was significantly enhanced compared with WT rings. The contraction due to CCE induced by passive store depletion, however, was comparable between WT and p75(-/-) rings. Active tension induced by serotonin, U-46619 (a thromboxane A(2) analog), thrombin, 4-aminopyridine (a K(+) channel blocker), and high extracellular K(+) in p75(-/-) rings was similar to that in WT rings. Deletion of p75(NTR) did not alter pulmonary vasodilation to sodium nitroprusside (a nitric oxide donor). These data suggest that intact p75(NTR) signaling may play a role in modulating pulmonary vasoconstriction induced by endothelin-1 and by active store depletion.
Project description:P75 neurotrophic receptor (p75NTR) is an important receptor for the role of neurotrophins in modulating brain plasticity and apoptosis. The current understanding of the role of p75NTR in cellular adaptation following pathological insults remains blurred, which makes p75NTR's related signaling networks an interesting and challenging initial point of investigation. We identified p75NTR and related genes through extensive data mining of a PubMed literature search including published works related to p75NTR from the past 20 years. Bioinformatic network and pathway analyses of identified genes (n = 235) were performed using ReactomeFIViz in Cytoscape based on the highly reliable Reactome functional interaction network algorithm. This approach merges interactions extracted from human curated pathways with predicted interactions from machine learning. Genome-wide pathway analysis showed total of 16 enriched hierarchical clusters. A total of 278 enriched single pathways were also identified (p < 0.05, false discovery rate corrected). Gene network analyses showed multiple known and new targets in the p75NTR gene network. This study provides a comprehensive analysis and investigation into the current knowledge of p75NTR signaling networks and pathways. These results also identify several genes and their respective protein products as involved in the p75NTR network, which have not previously been clearly studied in this pathway. These results can be used to generate novel hypotheses to gain a greater understanding of p75NTR in acute brain injuries, neurodegenerative diseases and general response to cellular damage.
Project description:Neurotrophins (NTs) promotes angiogenesis and EC survival, via tropomyosin kinase trkA and trkB receptors. A different p75NTR receptor of NTs, which belongs to the TNF-alfa receptor superfamily, is not or scarcely expressed by endothelial cells (EC) and endothelial progenitor cells (EPC) under basal conditions. Both diabetes and muscular ischemia induce p75NTR in capillary EC. In this study, by gene transfer, we forced the expression of p75NTR in EC and EPC to study the effect on cell survival, proliferation, adhesion, migration, and capillary-like tubes formation on matrigel, which all resulted impaired by p75NTR. We identified that p75NTR inhibits the VEGF-A/Akt/eNOS/NO pro-angiogenesis/pro-EC survival pathway and reduces the mRNA contents of survivin and securin in EC. By Illumina technology and real-time PCR, we found that p75-NTR alters the expression of VEGF-A and beta-1 integrin, which are implicated in angiogenesis and cell survival. p75NTR transfer to ischemic murine limb muscles impaired neoangiogenesis and blood flow recovery and induced apoptosis of bone marrow Sca-1+/Lin- progenitor cells. Diabetes induced p75NTR in bone marrow Sca-1+/Lin- cells and this correlated with apoptosis. Finally, inhibition of p75NTR signaling in diabetic ischemic limb muscles restored proper muscular neovascularization and blood flow recovery. Keywords: Response to ectopic receptor expression on angiogenesis
Project description:Insulin resistance is a key factor in the etiology of type 2 diabetes. Insulin-stimulated glucose uptake is mediated by the glucose transporter 4 (GLUT4), which is expressed mainly in skeletal muscle and adipose tissue. Insulin-stimulated translocation of GLUT4 from its intracellular compartment to the plasma membrane is regulated by small guanosine triphosphate hydrolases (GTPases) and is essential for the maintenance of normal glucose homeostasis. Here we show that the p75 neurotrophin receptor (p75(NTR)) is a regulator of glucose uptake and insulin resistance. p75(NTR) knockout mice show increased insulin sensitivity on normal chow diet, independent of changes in body weight. Euglycemic-hyperinsulinemic clamp studies demonstrate that deletion of the p75(NTR) gene increases the insulin-stimulated glucose disposal rate and suppression of hepatic glucose production. Genetic depletion or shRNA knockdown of p75(NTR) in adipocytes or myoblasts increases insulin-stimulated glucose uptake and GLUT4 translocation. Conversely, overexpression of p75(NTR) in adipocytes decreases insulin-stimulated glucose transport. In adipocytes, p75(NTR) forms a complex with the Rab5 family GTPases Rab5 and Rab31 that regulate GLUT4 trafficking. Rab5 and Rab31 directly interact with p75(NTR) primarily via helix 4 of the p75(NTR) death domain. Adipocytes from p75(NTR) knockout mice show increased Rab5 and decreased Rab31 activities, and dominant negative Rab5 rescues the increase in glucose uptake seen in p75(NTR) knockout adipocytes. Our results identify p75(NTR) as a unique player in glucose metabolism and suggest that signaling from p75(NTR) to Rab5 family GTPases may represent a unique therapeutic target for insulin resistance and diabetes.
Project description:Neurotrophins (NTs) promotes angiogenesis and EC survival, via tropomyosin kinase trkA and trkB receptors. A different p75NTR receptor of NTs, which belongs to the TNF-alfa receptor superfamily, is not or scarcely expressed by endothelial cells (EC) and endothelial progenitor cells (EPC) under basal conditions. Both diabetes and muscular ischemia induce p75NTR in capillary EC. In this study, by gene transfer, we forced the expression of p75NTR in EC and EPC to study the effect on cell survival, proliferation, adhesion, migration, and capillary-like tubes formation on matrigel, which all resulted impaired by p75NTR. We identified that p75NTR inhibits the VEGF-A/Akt/eNOS/NO pro-angiogenesis/pro-EC survival pathway and reduces the mRNA contents of survivin and securin in EC. By Illumina technology and real-time PCR, we found that p75-NTR alters the expression of VEGF-A and beta-1 integrin, which are implicated in angiogenesis and cell survival. p75NTR transfer to ischemic murine limb muscles impaired neoangiogenesis and blood flow recovery and induced apoptosis of bone marrow Sca-1+/Lin- progenitor cells. Diabetes induced p75NTR in bone marrow Sca-1+/Lin- cells and this correlated with apoptosis. Finally, inhibition of p75NTR signaling in diabetic ischemic limb muscles restored proper muscular neovascularization and blood flow recovery. Keywords: Response to ectopic receptor expression on angiogenesis Two series of 4 mice each were treated with either control adenovirus (AdNull) or adenovirus expressing neurotrophin p75 receptor (AdP75). Anaesthetized mice received 3 adenovirus injections (for a total of 109 p.f.u. virus in 20 micro L) into 3 equidistant sites of the normoperfused or ischemic left adductor muscles, as described (2. Emanueli C, Graiani G, Salis MB, Gadau S, Desortes E, Madeddu P. Prophylactic gene therapy with human tissue kallikrein ameliorates limb ischemia recovery in type 1 diabetic mice. Diabetes. 2004 Apr;53(4):1096-103. )
Project description:The intracellular domain of the p75 neurotrophin receptor (p75ICD) can be released by gamma-secretase in response to the previous activation of alpha-secretase by phorbol esters. However, ligand-dependent release of p75ICD has yet to be described. We show here that nerve growth factor can induce the release of p75ICD and facilitate its translocation to the nucleus in a gamma-secretase-dependent manner. This effect was observed in RN22 schwannoma cells cultured under serum-free conditions, as well as in Schwann cells, and it was mimicked by other neurotrophins, such as brain-derived neurotrophic factor or neurotrophin-3. Unlike other known examples of regulated intramembrane proteolysis, ligand-dependent release of p75ICD did not need the previous activation of alpha-secretase. These results suggest that nuclear translocation of p75ICD may represent a novel neurotrophin-mediated signaling pathway.
Project description:Facilitation of nerve growth factor (NGF) signaling by the p75 neurotrophin receptor (p75(NTR)) is critical for neuronal survival and differentiation. However, the interaction between p75(NTR) and TrkA receptors required for this activity is not understood. Here, we report that a specific 29-amino acid peptide derived from the intracellular domain fragment of p75(NTR) interacts with and potentiates binding of NGF to TrkA-expressing cells, leading to increased neurite outgrowth in sympathetic neurons as a result of enhanced Erk1/2 and Akt signaling. An endogenous intracellular domain fragment of p75(NTR) (p75(ICD)) containing these 29 amino acids is produced by regulated proteolysis of the full-length receptor. We demonstrate that generation of this fragment is a requirement for p75(NTR) to facilitate TrkA signaling in neurons and propose that the juxtamembrane region of p75(ICD) acts to cause a conformational change within the extracellular domain of TrkA. This finding provides new insight into the mechanism by which p75(NTR) and TrkA interact to enhance neurotrophic signaling.
Project description:The invasive nature of glioblastoma renders them incurable by current therapeutic interventions. Using a novel invasive human glioma model, we previously identified the neurotrophin receptor p75(NTR) (aka CD271) as a mediator of glioma invasion. Herein, we provide evidence that preventing phosphorylation of p75(NTR) on S303 by pharmacological inhibition of PKA, or by a mutational strategy (S303G), cripples p75(NTR)-mediated glioma invasion resulting in serine phosphorylation within the C-terminal PDZ-binding motif (SPV) of p75(NTR). Consistent with this, deletion (ΔSPV) or mutation (SPM) of the PDZ motif results in abrogation of p75(NTR)-mediated invasion. Using a peptide-based strategy, we identified PDLIM1 as a novel signaling adaptor for p75(NTR) and provide the first evidence for a regulated interaction via S425 phosphorylation. Importantly, PDLIM1 was shown to interact with p75(NTR) in highly invasive patient-derived glioma stem cells/tumor-initiating cells and shRNA knockdown of PDLIM1 in vitro and in vivo results in complete ablation of p75(NTR)-mediated invasion. Collectively, these data demonstrate a requirement for a regulated interaction of p75(NTR) with PDLIM1 and suggest that targeting either the PDZ domain interactions and/or the phosphorylation of p75(NTR) by PKA could provide therapeutic strategies for patients with glioblastoma.