151
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Eglen R, Reisine T. Drug discovery and the human kinome: Recent trends. Pharmacol Ther 2011; 130:144-56. [DOI: 10.1016/j.pharmthera.2011.01.007] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 01/03/2011] [Indexed: 01/04/2023]
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152
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Ochodnický P, Cruz CD, Yoshimura N, Michel MC. Nerve growth factor in bladder dysfunction: Contributing factor, biomarker, and therapeutic target. Neurourol Urodyn 2011; 30:1227-41. [DOI: 10.1002/nau.21022] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Accepted: 09/21/2010] [Indexed: 12/11/2022]
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153
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Taking pain out of NGF: a "painless" NGF mutant, linked to hereditary sensory autonomic neuropathy type V, with full neurotrophic activity. PLoS One 2011; 6:e17321. [PMID: 21387003 PMCID: PMC3046150 DOI: 10.1371/journal.pone.0017321] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 01/28/2011] [Indexed: 01/07/2023] Open
Abstract
During adulthood, the neurotrophin Nerve Growth Factor (NGF) sensitizes
nociceptors, thereby increasing the response to noxious stimuli. The
relationship between NGF and pain is supported by genetic evidence: mutations in
the NGF TrkA receptor in patients affected by an hereditary rare disease
(Hereditary Sensory and Autonomic Neuropathy type IV, HSAN IV) determine a
congenital form of severe pain insensitivity, with mental retardation, while a
mutation in NGFB gene, leading to the aminoacid substitution
R100W in mature NGF, determines a similar loss of pain
perception, without overt cognitive neurological defects (HSAN V). The R100W
mutation provokes a reduced processing of proNGF to mature NGF in cultured cells
and a higher percentage of neurotrophin secreted is in the proNGF form.
Moreover, using Surface Plasmon Resonance we showed that the R100W mutation does
not affect NGF binding to TrkA, while it abolishes NGF binding to p75NTR
receptors. However, it remains to be clarified whether the major impact of the
mutation is on the biological function of proNGF or of mature NGF and to what
extent the effects of the R100W mutation on the HSAN V clinical phenotype are
developmental, or whether they reflect an impaired effectiveness of NGF to
regulate and mediate nociceptive transmission in adult sensory neurons. Here we
show that the R100 mutation selectively alters some of the signaling pathways
activated downstream of TrkA NGF receptors. NGFR100 mutants maintain identical
neurotrophic and neuroprotective properties in a variety of cell assays, while
displaying a significantly reduced pain-inducing activity in
vivo (n = 8–10 mice/group). We also show
that proNGF has a significantly reduced nociceptive activity, with respect to
NGF. Both sets of results jointly contribute to elucidating the mechanisms
underlying the clinical HSAN V manifestations, and to clarifying which receptors
and intracellular signaling cascades participate in the pain sensitizing action
of NGF.
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154
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Stanzione F, Esposito L, Paladino A, Pedone C, Morelli G, Vitagliano L. Role of the conformational versatility of the neurotrophin N-terminal regions in their recognition by Trk receptors. Biophys J 2011; 99:2273-8. [PMID: 20923662 DOI: 10.1016/j.bpj.2010.07.054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Revised: 07/14/2010] [Accepted: 07/23/2010] [Indexed: 01/08/2023] Open
Abstract
Neurotrophins (NTs) represent a family of proteins that play an important role in the survival, development, and function of neurons. Extensive efforts are currently being made to develop small molecules endowed with agonist or antagonist NT activity. The structurally versatile N-termini of these proteins are considered regions of interest for the design of new molecules. By combining experimental and computational approaches, we analyzed the intrinsic conformational preferences of the N-termini of two of the most important NTs: NGF (NGF-Nter) and NT4 (NT4-Nter). Circular dichroism spectra clearly indicate that both peptides show a preference for random coil states. Because this finding does not preclude the possibility that structured forms may occur in solution as minor conformational states, we performed molecular-dynamics simulations to gain insights into the structural features of populated species. In line with the circular dichroism analysis, the simulations show a preference for unstructured states for both peptides. However, the simulations also show that for NT4-Nter, and to a lesser extent for NGF-Nter, helical conformations, which are required for binding to the Trk receptor, are present in the repertoire of structures that are intrinsically accessible to these peptides. Accordingly, molecular recognition of NTs by the Trk receptor is accomplished by the general mechanism known as population shift. These findings provide a structural rationale for the observed activity of synthetic peptides based on these NT regions. They also suggest strategies for the development of biologically active peptide-based compounds.
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Affiliation(s)
- Francesca Stanzione
- Istituto di Biostrutture e Bioimmagini, Consiglio Nazionale delle Recerche, Naples, Italy
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155
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Michaelsen K, Zagrebelsky M, Berndt-Huch J, Polack M, Buschler A, Sendtner M, Korte M. Neurotrophin receptors TrkB.T1 and p75NTR cooperate in modulating both functional and structural plasticity in mature hippocampal neurons. Eur J Neurosci 2010; 32:1854-65. [PMID: 20955473 DOI: 10.1111/j.1460-9568.2010.07460.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
Tropomyosin-related kinase (Trk) receptors modulate neuronal structure and function both during development and in the mature nervous system. Interestingly, TrkB and TrkC are expressed as full-length and as truncated splice variants. The cellular function of the kinase-lacking isoforms remains so far unclear. We investigated the role of the truncated receptor TrkB.T1 in the hippocampus of transgenic mice overexpressing this splice variant by analyzing both neuronal structure and function. We observed an impairment in activity-dependent synaptic plasticity as indicated by deficits in long-term potentiation and long-term depression in acute hippocampal slices of transgenic TrkB.T1 mice. In addition, dendritic complexity and spine density were significantly altered in TrkB.T1-overexpressing CA1 neurons. We found that the effect of TrkB.T1 overexpression differs between subgroups of CA1 neurons. Remarkably, overexpression of p75(NTR) and its activation by chemical induction of long-term depression in slice cultures rescued the TrkB.T1-dependent morphological alterations specifically in one of the two subgroups observed. These findings suggest that the TrkB.T1 and p75(NTR) receptor signaling systems might be cross-linked. Our findings demonstrate that TrkB.T1 regulates the function and the structure of mature pyramidal neurons. In addition, we showed that the ratio of expression levels of p75(NTR) and TrkB.T1 plays an important role in modulating dendritic architecture and synaptic plasticity in the adult rodent hippocampus, and, indeed, that the endogenous expression patterns of both receptors change reciprocally over time. We therefore propose a new function of TrkB.T1 as being dominant-negative to p75(NTR).
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Affiliation(s)
- K Michaelsen
- TU Braunschweig, Zoological Institute, Cellular Neurobiology, Braunschweig, Germany
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156
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Abstract
Recent structural studies of receptor tyrosine kinases (RTKs) have revealed unexpected diversity in the mechanisms of their activation by growth factor ligands. Strategies for inducing dimerization by ligand binding are surprisingly diverse, as are mechanisms that couple this event to activation of the intracellular tyrosine kinase domains. As our understanding of these details becomes increasingly sophisticated, it provides an important context for therapeutically countering the effects of pathogenic RTK mutations in cancer and other diseases. Much remains to be learned, however, about the complex signaling networks downstream from RTKs and how alterations in these networks are translated into cellular responses.
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157
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Montaño JA, Pérez-Piñera P, García-Suárez O, Cobo J, Vega JA. Development and neuronal dependence of cutaneous sensory nerve formations: Lessons from neurotrophins. Microsc Res Tech 2010; 73:513-29. [PMID: 19839059 DOI: 10.1002/jemt.20790] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Null mutations of genes from the NGF family of NTs and their receptors (NTRs) lead to loss/reduction of specific neurons in sensory ganglia; conversely, cutaneous overexpression of NTs results in skin hyperinnervation and increase or no changes in the number of sensory neurons innervating the skin. These neuronal changes are paralleled with loss of specific types of sensory nerve formations in the skin. Therefore, mice carrying mutations in NT or NTR genes represent an ideal model to identify the neuronal dependence of each type of cutaneous sensory nerve ending from a concrete subtype of sensory neuron, since the development, maintenance, and structural integrity of sensory nerve formations depend upon sensory neurons. Results obtained from these mouse strains suggest that TrkA positive neurons are connected to intraepithelial nerve fibers and other sensory nerve formations depending from C and Adelta nerve fibers; the neurons expressing TrkB and responding to BDNF and NT-4 innervate Meissner corpuscles, a subpopulation of Merkell cells, some mechanoreceptors of the piloneural complex, and the Ruffini's corpuscles; finally, a subpopulation of neurons, which are responsive to NT-3, support postnatal survival of some intraepithelial nerve fibers and Merkel cells in addition to the muscle mechanoreceptors. On the other hand, changes in NTs and NTRs affect the structure of non-nervous structures of the skin and are at the basis of several cutaneous pathologies. This review is an update about the role of NTs and NTRs in the maintenance of normal cutaneous innervation and maintenance of skin integrity.
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Affiliation(s)
- Juan A Montaño
- Departamento de Ciencias de la Salud, Universidad Católica San Antonio, Murcia, Spain
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158
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Simi A, Ibáñez CF. Assembly and activation of neurotrophic factor receptor complexes. Dev Neurobiol 2010; 70:323-31. [PMID: 20186713 DOI: 10.1002/dneu.20773] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Neurotrophic factors play important roles in the development and function of both neuronal and glial elements of the central and peripheral nervous systems. Their functional diversity is in part based on their ability to interact with alternative complexes of receptor molecules. This review focuses on our current understanding of the mechanisms that govern the assembly and activation of neurotrophic factor receptor complexes. The realization that many, if not the majority, of these complexes exist in a preassembled form at the plasma membrane has forced the revision of classical ligand-mediated oligomerization models, and led to the discovery of novel mechanisms of receptor activation and generation of signaling diversity which are likely to be shared by many different classes of receptors.
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Affiliation(s)
- Anastasia Simi
- Division of Molecular Neurobiology, Department of Neuroscience, Karolinska Institutet, Stockholm S-17177, Sweden
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159
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Teng KK, Felice S, Kim T, Hempstead BL. Understanding proneurotrophin actions: Recent advances and challenges. Dev Neurobiol 2010; 70:350-9. [PMID: 20186707 DOI: 10.1002/dneu.20768] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neurotrophins are initially synthesized as larger precursors (proneurotrophins), which undergo proteolytic cleavage to yield mature forms. Although the functions of the mature neurotrophins have been well established during neural development and in the adult nervous system, roles for the proneurotrophins in developmental and injury-induced cell death, as well as in synaptic plasticity, have only recently been appreciated. Interestingly, both mature neurotrophins and proneurotrophins utilize dual-receptor complexes to mediate their actions. The mature neurotrophin coreceptors consist of the Trk receptor tyrosine kinases and p75(NTR), wherein Trk transduces survival and differentiative signaling, and p75(NTR) modulates the affinity and selectivity of Trk activation. On the other hand, proneurotrophins engage p75(NTR) and the structurally distinct coreceptor sortilin, to initiate p75(NTR)-dependent signal transduction cascade. Although the specificity of mature neurotrophins vs. proneurotrophins actions is due in part to the formation of distinct coreceptor complexes, a number of recent studies highlight how different p75(NTR)-mediated cellular actions are modulated. Here, we review emerging evidence for a novel transmembrane mechanism for ligand-specific p75(NTR) activation and several mechanisms by which p75(NTR)-dependent apoptotic and nonapoptotic responses can be selective activated.
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Affiliation(s)
- Kenneth K Teng
- Department of Medicine, Weill Cornell Medical College, New York, New York 10065, USA
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160
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Fobian K, Owczarek S, Budtz C, Bock E, Berezin V, Pedersen MV. Peptides derived from the solvent-exposed loops 3 and 4 of BDNF bind TrkB and p75(NTR) receptors and stimulate neurite outgrowth and survival. J Neurosci Res 2010; 88:1170-81. [PMID: 19908279 DOI: 10.1002/jnr.22285] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Brain-derived neurotrophic factor (BDNF) is critically involved in modeling the developing nervous system and is an important regulator of a variety of crucial functions in the mature CNS. BDNF exerts its action through interactions with two transmembrane receptors, either separately or in concert. BDNF has been implicated in several neurological disorders, and irregularities in BDNF function may have severe consequences. Administration of BDNF as a drug has thus far yielded few practicable results, and the potential side effects when using a multifunctional protein are substantial. In an effort to produce more specific compounds without side effects, small peptides mimicking protein function have been developed. The present study characterized two mimetic peptides, Betrofin 3 and Betrofin 4, derived from the BDNF sequence. Both Betrofins bound the cognate BDNF receptors, TrkB and p75(NTR), and induced neurite outgrowth and enhanced neuronal survival, probably by inducing signaling through tha Akt and MAPK pathways. Distinct, charged residues within the Betrofin sequences were identified as important for generating the neuritogenic response, which was also inhibited when BDNF was added together with either Betrofin, indicating partial agonistic effects of the peptides. Thus, two peptides derived from BDNF induced neurite outgrowth and enhanced neuronal survival, probably through binding to BDNF receptors.
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Affiliation(s)
- Kristina Fobian
- Protein Laboratory, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Denmark
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161
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Brahimi F, Liu J, Malakhov A, Chowdhury S, Purisima EO, Ivanisevic L, Caron A, Burgess K, Saragovi HU. A monovalent agonist of TrkA tyrosine kinase receptors can be converted into a bivalent antagonist. Biochim Biophys Acta Gen Subj 2010; 1800:1018-26. [PMID: 20600627 DOI: 10.1016/j.bbagen.2010.06.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 05/28/2010] [Accepted: 06/11/2010] [Indexed: 01/18/2023]
Abstract
BACKGROUND Receptor tyrosine kinases (RTK) act through dimerization. Previously it was thought that only bivalent ligands could be agonistic, whereas monovalent ligands should be antagonistic. This notion changed after the demonstration that monovalent ligands can be agonistic, including our report of a small molecule monovalent ligand "D3" that is a partial agonist of the NGF receptor TrkA. A bivalent "D3-linker-D3" was expected to increase agonism. METHODS Dimeric analogs were synthesized and tested in binding, biochemical, and biological assays. RESULTS One analog, 1-ss, binds TrkA with higher affinity than D3 and induces or stabilizes receptor dimers. However, 1-ss exhibited antagonistic activity, through two mechanisms. One mechanism is that 1-ss blocks NGF binding, unlike D3 which is non-competitive. Inhibition of NGF binding may be due to the linker of 1-ss filling the inter-receptor space that NGF traverses before docking. In a second mechanism, 1-ss acts as a pure antagonist, inhibiting NGF-independent TrkA activity in cells over-expressing receptors. Inhibition is likely due to 1-ss "freezing" the TrkA dimer in the inactive state. CONCLUSIONS Dimerization of an RTK can result in antagonism, through two independent mechanisms. GENERAL SIGNIFICANCE we report a small molecule monovalent agonist being converted to a bivalent antagonist.
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Affiliation(s)
- Fouad Brahimi
- Lady Davis Institute-Jewish General Hospital, Pharmacology and Therapeutics, Oncology and the Cancer Center. McGill University, Canada
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162
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Ceni C, Kommaddi RP, Thomas R, Vereker E, Liu X, McPherson PS, Ritter B, Barker PA. The p75NTR intracellular domain generated by neurotrophin-induced receptor cleavage potentiates Trk signaling. J Cell Sci 2010; 123:2299-307. [PMID: 20530577 DOI: 10.1242/jcs.062612] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The p75 neurotrophin receptor (p75NTR) potentiates Trk signaling, but the underlying mechanisms remain uncertain. Here, we examine the relationship between p75NTR cleavage and Trk signaling. We found that, in PC12 cells, nerve growth factor (NGF) induces rapid and robust alpha-secretase- and gamma-secretase-dependent cleavage of p75NTR, releasing the resulting intracellular domain into the cytosol. Brain-derived neurotrophic factor similarly induces p75NTR cleavage in primary cerebellar granule neurons. p75NTR cleavage occurs by means of Trk-dependent activation of MEK-Erk signaling and induction of alpha-secretase activity, and is independent of ligand binding to p75NTR. Neurons and PC12 cells lacking p75NTR display defects in neurotrophin-dependent Akt activation. Normal Akt activation is rescued using full-length p75NTR or the p75 intracellular domain, but not cleavage-resistant p75NTR. We then demonstrate that NGF-dependent growth arrest of PC12 cells requires p75NTR cleavage and generation of the intracellular domain. We conclude that generation of the soluble p75NTR intracellular domain by Trk-induced cleavage plays a fundamental role in Trk-dependent signaling events.
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Affiliation(s)
- Claire Ceni
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Quebec H3A 2B4, Canada
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163
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Reddy EM, Chettiar ST, Kaur N, Shepal V, Shiras A. Dlxin-1, a MAGE family protein, induces accelerated neurite outgrowth and cell survival by enhanced and early activation of MEK and Akt signalling pathways in PC12 cells. Exp Cell Res 2010; 316:2220-36. [PMID: 20595047 DOI: 10.1016/j.yexcr.2010.05.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 04/30/2010] [Accepted: 05/25/2010] [Indexed: 10/19/2022]
Abstract
Dlxin-1 (also known as NRAGE or MAGED1) is a member of Type II melanoma-associated antigen (MAGE) family of proteins characterized by presence of a unique region of about 200 amino acids known as the MAGE homology domain (MHD). Dlxin-1 is associated with a large number of diverse cellular functions ranging from transcriptional regulation, cell cycle progression and differentiation to developmental apoptosis. While there are numerous studies reporting the role of NRAGE in facilitating cell death by interaction with p75NTR, we found varied effects of Dlxin-1 over-expression on PC12 cells grown in presence of NGF. These include induction of increased cell survival in presence of NGF and accelerated neuronal differentiation. We here categorically demonstrate that the effects on neuritogenesis are promoted through interactions of Dlxin-1 with the neurotrophin receptor TrkA. Further, using pharmacological inhibitors to specific pathways, we delineate the effects on enhanced neuritogenesis to the early and sustained activation of MEK pathway whereas the effects on cell survival to the early activation of Akt pathway. Next, we demonstrate a physical interaction of necdin with Dlxin-1 in PC12 cells. Our results establish that Dlxin-1 is an enhancer of neuronal differentiation and suggests that its possible interaction with NGF and necdin is critical in mediating pathways involved in neuronal survival and differentiation. Further in-depth analyses of the activation of various signalling pathways mediated through interaction with Dlxin-1 may provide valuable insight on the mechanisms that govern decisions regarding neuronal survival, growth, differentiation or apoptosis.
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Affiliation(s)
- E Maheswara Reddy
- National Centre for Cell Science (NCCS), NCCS Complex, University of Pune Campus, Ganeshkhind, Pune 411007, Maharashtra, India.
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164
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Arrighi N, Bodei S, Zani D, Simeone C, Cunico SC, Missale C, Spano P, Sigala S. Nerve growth factor signaling in prostate health and disease. Growth Factors 2010; 28:191-201. [PMID: 20166899 DOI: 10.3109/08977190903578678] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The prostate is one of the most abundant sources of nerve growth factor (NGF) in different species, including humans. NGF and its receptors are implicated in the control of prostate cell proliferation and apoptosis and it can either support or suppress cell growth. The co-expression of both NGF receptors, p75(NGFR) and tropomyosin-related kinase A (trkA), represents a crucial condition for the antiproliferative effect of NGF; indeed, p75(NGFR) is progressively lost during prostate tumorigenesis and its disappearance represents a malignancy marker of prostate adenocarcinoma (PCa). Interestingly, a dysregulation of NGF signal transduction was found in a number of human tumors. This review summarizes the current knowledge on the role of NGF and its receptors in prostate and in PCa. Conclusions bring to the hypothesis that the NGF network could be a candidate for future pharmacological manipulation in the PCa therapy: in particular the re-expression of p75(NTR) and/or the negative modulation of trkA could represent a target to induce apoptosis and to reduce proliferation and invasiveness of PCa.
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Affiliation(s)
- Nicola Arrighi
- Division of Urology, University of Brescia Medical School, P.le Spedali Civili 1, 25124 Brescia, Italy
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165
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Sugiura A, Ohtori S, Yamashita M, Yamauchi K, Inoue G, Suzuki M, Norimoto M, Orita S, Eguchi Y, Kuniyoshi K, Ochiai N, Kishida S, Takaso M, Aoki Y, Ishikawa T, Arai G, Miyagi M, Kamoda H, Nakamura J, Takahashi K. Effect of applying p75NTR saporin to a punctured intervertebral disc on calcitonin gene-related peptide expression in rat dorsal root ganglion neurons. J Orthop Sci 2010; 15:407-13. [PMID: 20559810 DOI: 10.1007/s00776-010-1469-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2009] [Accepted: 02/26/2010] [Indexed: 10/19/2022]
Abstract
BACKGROUND Recent studies have revealed that the low-affinity nerve growth factor receptor, p75 neurotrophin receptor (p75NTR), is important in inflammatory pain. Moreover, p75NTR immunoreactive sensory nerve and dorsal root ganglion (DRG) neurons have been found to innervate lumbar intervertebral discs. The purpose of the current study was to investigate the effect of p75NTR saporin, a toxin used to destroy p75NTR, on calcitonin gene-related peptide (CGRP), an inflammatory neuropeptide associated with pain, in DRG neurons innervating punctured intervertebral discs in rats. METHODS The neurotracer fluorogold (FG) was applied to the surfaces of L5/6 discs to label their innervating DRG neurons (n = 30). Of 30 rats, 10 were in a nonpunctured disc sham surgery control group (nonpuncture group), and the other 20 were in experimental groups in which intervertebral discs were punctured with a 23-gauge needle. p75NTR saporin was applied to the discs of 10 rats (puncture + p75NTR saporin group) and the other 10 received the same volume of saline (puncture + saline group). At 14 days after surgery, DRGs from L1 to L6 were harvested, sectioned, and immunostained for CGRP, and the proportions of CGRP-immunoreactive DRG neurons was evaluated. RESULTS Of the FG-labeled neurons innervating the L5/6 disc, the proportion of CGRP-immunoreactive neurons was 32% +/- 6% (mean +/- SE) in the nonpuncture group, 47.2% +/- 8% in the puncture + saline group, and 34.6% +/- 9% in the puncture + p75NTR saporin group. The proportion of CGRP-immunoreactive neurons was significantly greater in the puncture + saline group compared with the nonpuncture and puncture + p75NTR saporin groups (P < 0.01). CONCLUSIONS Half of the DRG neurons innervating the discs were positive for CGRP in the puncture + saline group. CGRP is important for mediating inflammatory and nerve-injured pain and may be important in discogenic pain. However, p75NTR saporin suppressed CGRP expression in DRG neurons. Therefore, p75NTR may be an important receptor for mediating discogenic pain via CGRP expression.
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Affiliation(s)
- Ai Sugiura
- Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, Chuo-ku, Chiba, Japan
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166
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Lamour G, Eftekhari-Bafrooei A, Borguet E, Souès S, Hamraoui A. Neuronal adhesion and differentiation driven by nanoscale surface free-energy gradients. Biomaterials 2010; 31:3762-71. [DOI: 10.1016/j.biomaterials.2010.01.099] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Accepted: 01/15/2010] [Indexed: 11/29/2022]
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167
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Massa SM, Yang T, Xie Y, Shi J, Bilgen M, Joyce JN, Nehama D, Rajadas J, Longo FM. Small molecule BDNF mimetics activate TrkB signaling and prevent neuronal degeneration in rodents. J Clin Invest 2010; 120:1774-85. [PMID: 20407211 DOI: 10.1172/jci41356] [Citation(s) in RCA: 301] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 02/17/2010] [Indexed: 02/01/2023] Open
Abstract
Brain-derived neurotrophic factor (BDNF) activates the receptor tropomyosin-related kinase B (TrkB) with high potency and specificity, promoting neuronal survival, differentiation, and synaptic function. Correlations between altered BDNF expression and/or function and mechanism(s) underlying numerous neurodegenerative conditions, including Alzheimer disease and traumatic brain injury, suggest that TrkB agonists might have therapeutic potential. Using in silico screening with a BDNF loop-domain pharmacophore, followed by low-throughput in vitro screening in mouse fetal hippocampal neurons, we have efficiently identified small molecules with nanomolar neurotrophic activity specific to TrkB versus other Trk family members. Neurotrophic activity was dependent on TrkB and its downstream targets, although compound-induced signaling activation kinetics differed from those triggered by BDNF. A selected prototype compound demonstrated binding specificity to the extracellular domain of TrkB. In in vitro models of neurodegenerative disease, it prevented neuronal degeneration with efficacy equal to that of BDNF, and when administered in vivo, it caused hippocampal and striatal TrkB activation in mice and improved motor learning after traumatic brain injury in rats. These studies demonstrate the utility of loop modeling in drug discovery and reveal what we believe to be the first reported small molecules derived from a targeted BDNF domain that specifically activate TrkB.We propose that these compounds constitute a novel group of tools for the study of TrkB signaling and may provide leads for developing new therapeutic agents for neurodegenerative diseases.
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Affiliation(s)
- Stephen M Massa
- Department of Neurology and Laboratory for Computational Neurochemistry and Drug Discovery, UCSF, San Francisco, California, USA
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168
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Baeza JL, Bonache MÁ, García-López MT, González-Muñiz R, Martín-Martínez M. 2-Alkyl-2-carboxyazetidines as γ-turn inducers: incorporation into neurotrophin fragments. Amino Acids 2010; 39:1299-307. [DOI: 10.1007/s00726-010-0569-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Accepted: 03/13/2010] [Indexed: 10/19/2022]
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169
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Cazorla M, Jouvenceau A, Rose C, Guilloux JP, Pilon C, Dranovsky A, Prémont J. Cyclotraxin-B, the first highly potent and selective TrkB inhibitor, has anxiolytic properties in mice. PLoS One 2010; 5:e9777. [PMID: 20333308 PMCID: PMC2841647 DOI: 10.1371/journal.pone.0009777] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Accepted: 02/19/2010] [Indexed: 11/19/2022] Open
Abstract
In the last decades, few mechanistically novel therapeutic agents have been developed to treat mental and neurodegenerative disorders. Numerous studies suggest that targeting BDNF and its TrkB receptor could be a promising therapeutic strategy for the treatment of brain disorders. However, the development of potent small ligands for the TrkB receptor has proven to be difficult. By using a peptidomimetic approach, we developed a highly potent and selective TrkB inhibitor, cyclotraxin-B, capable of altering TrkB-dependent molecular and physiological processes such as synaptic plasticity, neuronal differentiation and BDNF-induced neurotoxicity. Cyclotraxin-B allosterically alters the conformation of TrkB, which leads to the inhibition of both BDNF-dependent and -independent (basal) activities. Finally, systemic administration of cyclotraxin-B to mice results in TrkB inhibition in the brain with specific anxiolytic-like behavioral effects and no antidepressant-like activity. This study demonstrates that cyclotraxin-B might not only be a powerful tool to investigate the role of BDNF and TrkB in physiology and pathology, but also represents a lead compound for the development of new therapeutic strategies to treat brain disorders.
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Affiliation(s)
- Maxime Cazorla
- Neurobiology & Molecular Pharmacology, Centre de Psychiatrie et de Neurosciences, UMR-894 INSERM/Université Paris Descartes, Paris, France.
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170
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Guillemard V, Ivanisevic L, Garcia AG, Scholten V, Lazo OM, Bronfman FC, Saragovi HU. An agonistic mAb directed to the TrkC receptor juxtamembrane region defines a trophic hot spot and interactions with p75 coreceptors. Dev Neurobiol 2010; 70:150-64. [PMID: 19953569 DOI: 10.1002/dneu.20776] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The D5 domain of TrkC receptors is a docking site for Neurotrophin-3 (NT-3), but other domains may be relevant for function or harmonizing signals with p75(NTR) coreceptors. We report a monoclonal antibody (mAb) 2B7 targeting the juxtamembrane domain of TrkC. mAb 2B7 binds to murine and human TrkC receptors and is a functional agonist that affords activation of TrkC, AKT, and MAPK. These signals result in cell survival but not in cellular differentiation. Monomeric 2B7 Fabs also affords cell survival. Binding of 2B7 mAb and 2B7 Fabs to TrkC are blocked by NT-3 in a dose-dependent manner but not by pro-NT-3. Expression of p75(NTR) coreceptors on the cell surface block the binding and function of mAb 2B7, whereas NT-3 binding and function are enhanced. mAb 2B7 defines a previously unknown neurotrophin receptor functional hot spot; that exclusively generates survival signals; that can be activated by non-dimeric ligands; and potentially unmasks a site for p75-TrkC interactions.
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Affiliation(s)
- Veronique Guillemard
- Department of Pharmacology and Therapeutics, Lady Davis Research Institute-Jewish General Hospital, McGill University, Montreal, Quebec, Canada
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171
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Scott ALM, Ramer MS. Schwann cell p75NTR prevents spontaneous sensory reinnervation of the adult spinal cord. Brain 2010; 133:421-32. [PMID: 20047901 DOI: 10.1093/brain/awp316] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Schwann cells are attractive candidates for repair of the injured spinal cord. Transplanted Schwann cells are permissive to regeneration, but their ability to promote regeneration into distal spinal cord remains weak despite their production of growth-promoting neurotrophins. Schwann cell activation such as that which accompanies peripheral nerve injury results in massive upregulation of the p75(NTR) pan-neurotrophin-receptor. Here we test the hypothesis that this p75(NTR) upregulation following dorsal root injury limits availability of endogenous neurotrophin to axons and restricts regeneration of injured axons into the spinal cord. We injured dorsal roots (fourth cervical to second thoracic) in mice lacking the neurotrophin-binding domain of p75(NTR) and in wild-type littermates. Axonal regeneration was assessed by selective tracing of neurotrophin-responsive and non-responsive dorsal root ganglion neurons. Functional reinnervation of the spinal cord was assessed in behavioural experiments and via Fos immunohistochemistry following formalin injection into the forepaw. We also measured levels of nerve growth factor and neurotrophin-3 following nerve injury in knockout and wild-type mice, and used Trk-Fc receptor chimeras to block nerve growth factor and neurotrophin-3 signalling in dorsal root ganglion/Schwann cell co-cultures and following dorsal root injury in vivo. The roles of neuronal and glial p75(NTR) were assessed in transplant experiments in vivo and in co-cultures. We found that nerve growth factor and neurotrophin-3-responsive axons regenerated into the spinal cord of p75(NTR) knockout mice where they made functional connections with dorsal horn neurons. Despite equivalent levels of nerve growth factor and neurotrophin-3 in wild-type and knockout mice, successful regeneration in knockouts was neurotrophin-dependent. Transplantation of p75(-/-) neurons into a wild-type environment, p75(-/-) peripheral nerve grafts into the injured p75(+/+) spinal cord, and dissociated sensory neuron/Schwann cell co-cultures showed that the absence of p75(NTR) from glia, not from neurons, promotes regeneration. These findings indicate that Schwann cell p75(NTR) restricts neurotrophin availability to the extent that it prevents spontaneous sensory axon regeneration into the spinal cord. The implication is that inactivating p75(NTR) in Schwann (or olfactory ensheathing) cells may enable axons to grow beyond transplants, improving the outcome of spinal cord injury.
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172
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Iwakura N, Ohtori S, Orita S, Yamashita M, Takahashi K, Kuniyoshi K. Role of low-affinity nerve growth factor receptor inhibitory antibody in reducing pain behavior and calcitonin gene-related Peptide expression in a rat model of wrist joint inflammatory pain. J Hand Surg Am 2010; 35:267-73. [PMID: 20060234 DOI: 10.1016/j.jhsa.2009.10.030] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 10/23/2009] [Accepted: 10/26/2009] [Indexed: 02/02/2023]
Abstract
PURPOSE Nerve growth factor (NGF), via the high-affinity receptor, tyrosine kinase A, has been widely reported as a mediator of pain caused by inflammation. A clinical trial has suggested that anti-NGF antibody is effective for pain caused by osteoarthritis of the knee. However, adverse events such as headache (8.9%), upper respiratory tract infection (7.3%), and paresthesia (6.8%) were reported. We hypothesized that inhibition of the low-affinity NGF receptor, p75 neurotrophin receptor (p75NTR), is also effective for joint pain and may reduce side effects. This study examined suppression of pain behavior and expression of pain-inducing neuropeptides such as calcitonin gene-related peptide (CGRP) and p75NTR in dorsal root ganglia neurons by a p75NTR inhibitory antibody in a rat model of wrist joint inflammatory pain. METHODS We injected complete Freund's adjuvant (CFA) into the wrist joint of rats and used this as a model of inflammatory pain. We applied 10 microL of saline (CFA + saline group; n = 20) or 1, 10, or 50 microL of a p75NTR inhibitory antibody (CFA + p75NTR inhibitory antibody group; n = 40) directly to the inflamed joint in the rats. Mechanical hyperalgesia was measured for 2 weeks using von Frey filaments. We assessed CGRP and p75NTR expression in C8 dorsal root ganglia immunochemically. Adverse events such as loss of weight and/or appetite, constipation, and infection were examined. RESULTS p75NTR inhibitory antibody reduced mechanical hyperalgesia caused by CFA (p<.05 vs controls) in the rat model (p<.01 vs saline), without any adverse events. We found that 10 and 50 microL of a p75NTR inhibitory antibody were more effective for pain, without a significant difference between doses. CGRP and p75NTR immunoreactivity was upregulated in the CFA + saline groups compared with a control group (p<.01). However, direct p75NTR inhibitory antibody application decreased CGRP and p75NTR expression after wrist inflammation (p<.01). CONCLUSIONS p75NTR inhibition may be a therapeutic target for inflamed joint pain treatment with reduced adverse events.
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Affiliation(s)
- Nahoko Iwakura
- Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
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173
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Covaceuszach S, Capsoni S, Marinelli S, Pavone F, Ceci M, Ugolini G, Vignone D, Amato G, Paoletti F, Lamba D, Cattaneo A. In vitro receptor binding properties of a “painless” NGF mutein, linked to hereditary sensory autonomic neuropathy type V. Biochem Biophys Res Commun 2010; 391:824-9. [DOI: 10.1016/j.bbrc.2009.11.146] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Accepted: 11/21/2009] [Indexed: 01/03/2023]
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174
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Feng D, Kim T, Ozkan E, Light M, Torkin R, Teng KK, Hempstead BL, Garcia KC. Molecular and structural insight into proNGF engagement of p75NTR and sortilin. J Mol Biol 2009; 396:967-84. [PMID: 20036257 PMCID: PMC2847487 DOI: 10.1016/j.jmb.2009.12.030] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Accepted: 12/15/2009] [Indexed: 12/21/2022]
Abstract
Nerve growth factor (NGF) is initially synthesized as a precursor, proNGF, that is cleaved to release its C-terminal mature form. Recent studies suggested that proNGF is not an inactive precursor but acts as a signaling ligand distinct from its mature counterpart. proNGF and mature NGF initiate opposing biological responses by utilizing both distinct and shared receptor components. In this study, we carried out structural and biochemical characterization of proNGF interactions with p75NTR and sortilin. We crystallized proNGF complexed to p75NTR and present the structure at 3.75-A resolution. The structure reveals a 2:2 symmetric binding mode, as compared with the asymmetric structure of a previously reported crystal structure of mature NGF complexed to p75NTR and the 2:2 symmetric complex of neurotrophin-3 (NT-3) and p75NTR. Here, we discuss the possible origins and implications of the different stoichiometries. In the proNGF-p75NTR complex, the pro regions of proNGF are mostly disordered and two hairpin loops (loop 2) at the top of the NGF dimer have undergone conformational changes in comparison with mature NT structures, suggesting possible interactions with the propeptide. We further explored the binding characteristics of proNGF to sortilin using surface plasmon resonance and cell-based assays and determined that calcium ions promote the formation of a stable ternary complex of proNGF-sortilin-p75NTR. These results, together with those of previous structural and mechanistic studies of NT-receptor interactions, suggest the potential for distinct signaling activities through p75NTR mediated by different NT-induced conformational changes.
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Affiliation(s)
- Dan Feng
- Department of Cellular and Molecular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
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175
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Eibl JK, Chapelsky SA, Ross GM. Multipotent Neurotrophin Antagonist Targets Brain-Derived Neurotrophic Factor and Nerve Growth Factor. J Pharmacol Exp Ther 2009; 332:446-54. [DOI: 10.1124/jpet.109.159079] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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176
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Hindle KL, Bella J, Lovell SC. Quantitative analysis and prediction of curvature in leucine-rich repeat proteins. Proteins 2009; 77:342-58. [PMID: 19452560 DOI: 10.1002/prot.22440] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Leucine-rich repeat (LRR) proteins form a large and diverse family. They have a wide range of functions most of which involve the formation of protein-protein interactions. All known LRR structures form curved solenoids, although there is large variation in their curvature. It is this curvature that determines the shape and dimensions of the inner space available for ligand binding. Unfortunately, large-scale parameters such as the overall curvature of a protein domain are extremely difficult to predict. Here, we present a quantitative analysis of determinants of curvature of this family. Individual repeats typically range in length between 20 and 30 residues and have a variety of secondary structures on their convex side. The observed curvature of the LRR domains correlates poorly with the lengths of their individual repeats. We have, therefore, developed a scoring function based on the secondary structure of the convex side of the protein that allows prediction of the overall curvature with a high degree of accuracy. We also demonstrate the effectiveness of this method in selecting a suitable template for comparative modeling. We have developed an automated, quantitative protocol that can be used to predict accurately the curvature of leucine-rich repeat proteins of unknown structure from sequence alone. This protocol is available as an online resource at http://www.bioinf.manchester.ac.uk/curlrr/.
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Affiliation(s)
- K Lauren Hindle
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
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177
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Ely LK, Fischer S, Garcia KC. Structural basis of receptor sharing by interleukin 17 cytokines. Nat Immunol 2009; 10:1245-51. [PMID: 19838198 PMCID: PMC2783927 DOI: 10.1038/ni.1813] [Citation(s) in RCA: 142] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Accepted: 09/17/2009] [Indexed: 11/30/2022]
Abstract
T helper type 17 (TH-17) cells, together with their effector cytokines including interleukin 17 (IL-17) family members, are emerging as key mediators of chronic inflammatory and autoimmune disorders. Here we present the crystal structure of a 1:2 complex of IL-17RA bound to IL-17F. The manner of complex formation is unique for cytokines, and involves two fibronectin-type domains of IL-17RA engaging IL-17 within a groove between the IL-17 homodimer interface in a knob-and-hole fashion. The first receptor-binding event to the IL-17 cytokines modulates the affinity and specificity of the second receptor-binding event, thereby promoting heterodimeric versus homodimeric complex formation. IL-17RA utilizes a common recognition strategy to bind to several IL-17 family members, allowing it to potentially act as a shared receptor within multiple different signaling complexes.
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Affiliation(s)
- Lauren K Ely
- Howard Hughes Medical Institute, Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California, USA
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178
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Haas SL, Fitzner B, Jaster R, Wiercinska E, Gaitantzi H, Jesnowski R, Löhr JM, Singer MV, Dooley S, Breitkopf K. Transforming growth factor-beta induces nerve growth factor expression in pancreatic stellate cells by activation of the ALK-5 pathway. Growth Factors 2009; 27:289-99. [PMID: 19639490 DOI: 10.1080/08977190903132273] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Nerve growth factor (NGF), a survival factor for neurons enforces pain by sensitizing nociceptors. Also in the pancreas, NGF was associated with pain and it can stimulate the proliferation of pancreatic cancer cells. Hepatic stellate cells (HSC) respond to NGF with apoptosis. Transforming growth factor (TGF)-beta, one of the strongest pro-fibrogenic activators of pancreatic stellate cells (PSC) induced NGF and its two receptors in an immortalized human cell line (ihPSC) and primary rat PSC (prPSC) as determined by RT-PCR, western blot, and immunofluorescence. In contrast to HSC, PSC expressed both NGF receptors, although p75(NTR) expression was weak in prPSC. In contrast to ihPSC TGF-beta activated both Smad signaling cascades in prPSC. NGF secretion was diminished by the activin-like kinase (ALK)-5 inhibitor SB431542, indicating the predominant role of ALK5 in activating the NGF system in PSC. While NGF did not affect proliferation or survival of PSC it induced expression of Inhibitor of Differentiation-1. We conclude that under conditions of upregulated TGF-beta, like fibrosis, NGF levels will also increase in PSC which might contribute to pancreatic wound healing responses.
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Affiliation(s)
- Stephan L Haas
- Department of Medicine II, Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
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179
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Mahapatra S, Mehta H, Woo SB, Neet KE. Identification of critical residues within the conserved and specificity patches of nerve growth factor leading to survival or differentiation. J Biol Chem 2009; 284:33600-13. [PMID: 19762468 DOI: 10.1074/jbc.m109.058420] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Afflicted neurons in Alzheimer disease have been shown to display an imbalance in the expression of TrkA and p75(NTR) at the cell surface, and administration of nerve growth factor (NGF) has been considered and attempted for treatment. However, wild-type NGF causes extensive elaboration of neurites while providing survival support. This study was aimed at developing recombinant NGF muteins that did not support neuritogenesis while maintaining the survival response. Critical residues were identified at the ligand-receptor interface by point mutagenesis that played a greater importance in neuritogenesis versus survival. By combining point mutations, two survival-selective recombinant NGF muteins, i.e./7-84-103 and KKE/7-84-103, were generated. Both muteins reduced neuritogenesis in PC12 (TrkA(+)/p75(NTR+)) cells by >90%, while concurrently retaining near wild-type survival activity in MG139 (TrkA(+) only) and PCNA fibroblast (p75(NTR+)-only) cells. Additionally, survival in both naive and terminally differentiated PC12 cells was shown to be intermediate between NGF and negative controls. Dose-response curves with 7-84-103 showed that the differentiation curve was shifted by about 100-fold, whereas the EC(50) for survival was only increased by 3.3-fold. Surface plasmon resonance analysis revealed a 200-fold decrease in binding of 7-84-103 to TrkA. The retention of cell survival was attributed to maintenance of signaling through the Akt survival pathway with reduced MAPK signaling for differentiation. The effect of key mutations along the NGF receptor interface are transmitted inside the cell to enable the generation of survival-selective recombinant NGF muteins that may represent novel pharmacologic lead agents for the amelioration of Alzheimer disease.
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Affiliation(s)
- Sidharth Mahapatra
- Department of Biochemistry and Molecular Biology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
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180
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Hower AE, Beltran PJ, Bixby JL. Dimerization of tyrosine phosphatase PTPRO decreases its activity and ability to inactivate TrkC. J Neurochem 2009; 110:1635-47. [PMID: 19573017 DOI: 10.1111/j.1471-4159.2009.06261.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Receptor-protein tyrosine phosphatases (RPTPs), like receptor tyrosine kinases, regulate neuronal differentiation. While receptor tyrosine kinases are dimerized and activated by extracellular ligands, the extent to which RPTPs dimerize, and the effects of dimerization on phosphatase activity, are poorly understood. We have examined a neuronal type III RPTP, PTPRO; we find that PTPRO can form dimers in living cells, and that disulfide linkages in PTPROs intracellular domain likely regulate dimerization. Dimerization of PTPROs transmembrane and intracellular domains, achieved by ligand binding to a chimeric fusion protein, decreases activity toward artificial peptides and toward a putative substrate, tropomyosin-related kinase C (TrkC). Dephosphorylation of TrkC by PTPRO may be physiologically relevant, as it is efficient, and TrkC and PTPRO can be co-precipitated from transfected cells. Inhibition of PTPROs phosphatase activity by dimerization is interesting, as dimerization of a related RPTP, CD148/PTPRJ, increases activity. Thus, our results suggest a complex relationship between dimerization and activity in type III RPTPs.
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181
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Butowt R, von Bartheld CS. Fates of neurotrophins after retrograde axonal transport: phosphorylation of p75NTR is a sorting signal for delayed degradation. J Neurosci 2009; 29:10715-29. [PMID: 19710323 PMCID: PMC2761711 DOI: 10.1523/jneurosci.2512-09.2009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 07/15/2009] [Accepted: 07/20/2009] [Indexed: 12/16/2022] Open
Abstract
Neurotrophins can mediate survival or death of neurons. Opposing functions of neurotrophins are based on binding of these ligands to two distinct types of receptors: trk receptors and p75NTR. Previous work showed that target-derived NGF induces cell death, whereas BDNF and NT-3 enhance survival of neurons in the isthmo-optic nucleus of avian embryos. To determine the fate of retrogradely transported neurotrophins and test whether their sorting differs between neurotrophins mediating survival- or death-signaling pathways, we traced receptor-binding, sorting, and degradation kinetics of target-applied radiolabeled neurotrophins that bind in this system to trk receptors (BDNF, NT-3) or only to p75NTR (NGF). At the ultrastructural level, the p75NTR-bound NGF accumulates with a significant delay in multivesicular bodies and organelles of the degradation pathway on arrival in the cell body when compared with trk-bound BDNF or NT-3. This delayed lysosomal accumulation was restricted to target-derived NGF, but was not seen when NGF was supplied to the soma in vitro. The kinase inhibitors K252a and Gö6976 alter the kinetics of organelle accumulation: phosphorylation of p75NTR is a sorting signal for delayed sequestering of p75NTR-bound NGF in multivesicular bodies and delayed degradation in lysosomes when compared with trk-bound neurotrophins. Mutagenesis and mass spectrometry studies indicate that p75NTR is phosphorylated by conventional protein kinase C on serine 266. We conclude that, in addition to the known phosphorylation of trks, the phosphorylation of p75NTR can also significantly affect neuronal survival in vivo by changing the intracellular sorting and degradation kinetics of its ligands and thus signaling duration.
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Affiliation(s)
- Rafal Butowt
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557
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182
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Bayesian model predicts the response of axons to molecular gradients. Proc Natl Acad Sci U S A 2009; 106:10296-301. [PMID: 19541606 DOI: 10.1073/pnas.0900715106] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Axon guidance by molecular gradients plays a crucial role in wiring up the nervous system. However, the mechanisms axons use to detect gradients are largely unknown. We first develop a Bayesian "ideal observer" analysis of gradient detection by axons, based on the hypothesis that a principal constraint on gradient detection is intrinsic receptor binding noise. Second, from this model, we derive an equation predicting how the degree of response of an axon to a gradient should vary with gradient steepness and absolute concentration. Third, we confirm this prediction quantitatively by performing the first systematic experimental analysis of how axonal response varies with both these quantities. These experiments demonstrate a degree of sensitivity much higher than previously reported for any chemotacting system. Together, these results reveal both the quantitative constraints that must be satisfied for effective axonal guidance and the computational principles that may be used by the underlying signal transduction pathways, and allow predictions for the degree of response of axons to gradients in a wide variety of in vivo and in vitro settings.
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183
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Paoletti F, Covaceuszach S, Konarev PV, Gonfloni S, Malerba F, Schwarz E, Svergun DI, Cattaneo A, Lamba D. Intrinsic structural disorder of mouse proNGF. Proteins 2009; 75:990-1009. [PMID: 19089979 DOI: 10.1002/prot.22311] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The unprocessed precursor of the Nerve Growth Factor (NGF), proNGF, has additional functions, besides its initially described role as a chaperone for NGF folding. The precursor protein endows apoptotic and/or neurotrophic properties, in contrast to the mature part. The structural and molecular basis for such distinct activities are presently unknown. Aiming to gain insights into the specific molecular interactions that govern rm-proNGF biological activities versus those of its mature counterpart, a structural study by synchrotron small angle X-ray scattering (SAXS) in solution was carried out. The different binding properties of the two proteins were investigated by surface plasmon resonance (SPR) using, as structural probes, a panel of anti-NGF antibodies and the soluble forms of TrkA and p75(NTR) receptors. SAXS measurements revealed the rm-proNGF to be dimeric and anisometric, with the propeptide domain being intrinsically unstructured. Ab initio reconstructions assuming twofold symmetry generated two types of structural models, a globular "crab-like" and an elongated shape that resulted in equally good fits of the scattering data. A novel method accounting for possible coexistence of different conformations contributing to the experimental scattering pattern, with no symmetry constraints, suggests the "crab-like" to be a more likely proNGF conformation. To exploit the potential of chemical stabilizers affecting the existing conformational protein populations, SAXS data were also collected in the presence of ammonium sulphate. An increase of the proNGF compactness was observed. SPR data pinpoints that the propeptide of proNGF may act as an intrinsically unstructured protein domain, characterized by a molecular promiscuity in the interaction/binding to multiple partners (TrkA and p75(NTR) receptors and a panel of neutralizing anti-NGF antibodies) depending on the physiological conditions of the cell. These data provide a first insight into the structural basis for the selectivity of mouse short proNGF, versus NGF, towards its binding partners.
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Affiliation(s)
- Francesca Paoletti
- SISSA-ISAS, Building Q1, Area Science Park - Basovizza, S.S 14 Km 163.5, 34012 Trieste, Italy.
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184
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Abstract
The p75 neurotrophin receptor (p75(NTR)) is involved in numerous neuronal signaling paths but its fundamental signaling mechanisms are unknown. In this issue of Neuron, Vilar et al. show that p75NTR functions as a covalently crosslinked dimer to transduce NGF-induced signaling events.
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Affiliation(s)
- Philip A Barker
- Centre for Neuronal Survival, Montreal Neurological Institute, McGill University, 3801 University Avenue, Montreal, QC H3A 2B4, Canada.
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185
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Vilar M, Charalampopoulos I, Kenchappa RS, Simi A, Karaca E, Reversi A, Choi S, Bothwell M, Mingarro I, Friedman WJ, Schiavo G, Bastiaens PIH, Verveer PJ, Carter BD, Ibáñez CF. Activation of the p75 neurotrophin receptor through conformational rearrangement of disulphide-linked receptor dimers. Neuron 2009; 62:72-83. [PMID: 19376068 DOI: 10.1016/j.neuron.2009.02.020] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 11/14/2008] [Accepted: 02/25/2009] [Indexed: 11/27/2022]
Abstract
Ligand-mediated dimerization has emerged as a universal mechanism of growth factor receptor activation. Neurotrophins interact with dimers of the p75 neurotrophin receptor (p75(NTR)), but the mechanism of receptor activation has remained elusive. Here, we show that p75(NTR) forms disulphide-linked dimers independently of neurotrophin binding through the highly conserved Cys(257) in its transmembrane domain. Mutation of Cys(257) abolished neurotrophin-dependent receptor activity but did not affect downstream signaling by the p75(NTR)/NgR/Lingo-1 complex in response to MAG, indicating the existence of distinct, ligand-specific activation mechanisms for p75(NTR). FRET experiments revealed a close association of p75(NTR) intracellular domains that was transiently disrupted by conformational changes induced upon NGF binding. Although mutation of Cys(257) did not alter the oligomeric state of p75(NTR), the mutant receptor was no longer able to propagate conformational changes to the cytoplasmic domain upon ligand binding. We propose that neurotrophins activate p75(NTR) by a mechanism involving rearrangement of disulphide-linked receptor subunits.
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Affiliation(s)
- Marçal Vilar
- Division of Molecular Neurobiology, Department of Neuroscience, Karolinska Institute, 17177 Stockholm, Sweden
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186
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Lamour G, Journiac N, Souès S, Bonneau S, Nassoy P, Hamraoui A. Influence of surface energy distribution on neuritogenesis. Colloids Surf B Biointerfaces 2009; 72:208-18. [PMID: 19419846 DOI: 10.1016/j.colsurfb.2009.04.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 03/18/2009] [Accepted: 04/03/2009] [Indexed: 01/11/2023]
Abstract
PC12 cells are a useful model to study neuronal differentiation, as they can undergo terminal differentiation, typically when treated with nerve growth factor (NGF). In this study we investigated the influence of surface energy distribution on PC12 cell differentiation, by atomic force microscopy (AFM) and immunofluorescence. Glass surfaces were modified by chemisorption: an aminosilane, n-[3-(trimethoxysilyl)propyl]ethylendiamine (C(8)H(22)N(2)O(3)Si; EDA), was grafted by polycondensation. AFM analysis of substrate topography showed the presence of aggregates suggesting that the adsorption is heterogeneous, and generates local gradients in energy of adhesion. PC12 cells cultured on these modified glass surfaces developed neurites in absence of NGF treatment. In contrast, PC12 cells did not grow neurites when cultured in the absence of NGF on a relatively smooth surface such as poly-L-lysine substrate, where amine distribution is rather homogeneous. These results suggest that surface energy distribution, through cell-substrate interactions, triggers mechanisms that will drive PC12 cells to differentiate and to initiate neuritogenesis. We were able to create a controlled physical nano-structuration with local variations in surface energy that allowed the study of these parameters on neuritogenesis.
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Affiliation(s)
- Guillaume Lamour
- Laboratoire de Neuro-Physique Cellulaire, EA 3817, UFR Biomédicale, Université Paris Descartes, 45 rue des Saints-Pères, 75270 Paris Cedex 06, France
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187
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Johnson EC, Guo Y, Cepurna WO, Morrison JC. Neurotrophin roles in retinal ganglion cell survival: lessons from rat glaucoma models. Exp Eye Res 2009; 88:808-15. [PMID: 19217904 PMCID: PMC2704056 DOI: 10.1016/j.exer.2009.02.004] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 01/13/2009] [Accepted: 02/03/2009] [Indexed: 12/19/2022]
Abstract
The neurotrophin (NT) hypothesis proposes that the obstruction of retrograde transport at the optic nerve head results in the deprivation of neurotrophic support to retinal ganglion cells (RGC) leading to apoptotic cell death in glaucoma. An important corollary to this concept is the implication that appropriate enhancement of neurotrophic support will prolong the survival of injured RGC indefinitely. This hypothesis is, perhaps, the most widely recognized theory to explain RGC loss resulting from exposure of the eye to elevated intraocular pressure (IOP). Recent studies of NT signaling using rat glaucoma models, have examined the endogenous responses of the retina to pressure exposure as well as studies designed to augment NT signaling in order to rescue RGC from apoptosis following pressure-induced injury. The examination of these studies in this review reveals a number of consistent observations and provides direction for further investigations of this hypothesis.
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Affiliation(s)
- Elaine C Johnson
- The Kenneth C. Swan Ocular Neurobiology Laboratory, Casey Eye Institute, CERES, Oregon Health and Science University, Portland, OR 97239, USA.
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188
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Colquhoun A, Eibl JK, Krol KM, Chan HM, Ross GM. Conformational analysis of the effects of methylmercury on nerve growth factor and brain derived neurotrophic factor. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2009; 27:298-302. [PMID: 21783956 DOI: 10.1016/j.etap.2008.10.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 10/02/2008] [Accepted: 10/17/2008] [Indexed: 05/31/2023]
Abstract
Methylmercury is a neurotoxicant that is detrimental to the development and physiology of the nervous system. One possible mechanism for methylmercury's toxicity stems from its ability to interfere with the signaling of the neurotrophins nerve growth factor and brain derived neurotrophic factor. In this study, we examine the effect of methylmercury to determine if it interferes with neurotrophin conformation in a manner similar to Hg(2+), or if it occurs via an alternate mechanism. Our findings indicate that although MeHg inhibits neurotrophin signaling, its toxic effects are not mediated via an induced conformational change, as seen with other metal ions, including Hg(2+).
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Affiliation(s)
- Amy Colquhoun
- Northern Ontario School of Medicine, Laurentian University, Sudbury, Ontario, Canada P3E 2C6
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189
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Chen Y, Zeng J, Cen L, Chen Y, Wang X, Yao G, Wang W, Qi W, Kong K. Multiple roles of the p75 neurotrophin receptor in the nervous system. J Int Med Res 2009; 37:281-8. [PMID: 19383220 DOI: 10.1177/147323000903700201] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The p75 neurotrophin receptor (p75NTR) is a transmembrane protein that binds nerve growth factor (NGF) and has multiple functions in the nervous system where it is expressed widely during the developmental stages of life, although expression decreases dramatically by adulthood. Expression of p75NTR can increase in pathological states related to neural cell death. p75NTR is a member of the tumour necrosis factor (TNF) receptor family and it consists of intracellular, transmembrane and extracellular domains which are different from other TNF receptors. Either by interacting with tropomyosin receptor kinase (Trk) receptors or via the independent binding of neurotrophin, p75NTR can induce neurite outgrowth and cellular survival or cell apoptosis through several complicated signal transduction pathways. Most of these signalling pathways remain to be elucidated. By interacting with different cellular factors, p75NTR can induce neuron growth cone collapse or regrowth. p75NTR is also expressed in a variety of glial populations. The many functions of p75NTR require further study.
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Affiliation(s)
- Y Chen
- Department of Orthopaedics, The Second Affiliated Hospital, ShanTou University Medical College, Guangdong, China
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190
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Abstract
Neurotrophins were christened in consideration of their actions on the nervous system and, for a long time, they were the exclusive interest of neuroscientists. However, more recently, this family of proteins has been shown to possess essential cardiovascular functions. During cardiovascular development, neurotrophins and their receptors are essential factors in the formation of the heart and critical regulator of vascular development. Postnatally, neurotrophins control the survival of endothelial cells, vascular smooth muscle cells, and cardiomyocytes and regulate angiogenesis and vasculogenesis, by autocrine and paracrine mechanisms. Recent studies suggest the capacity of neurotrophins, via their tropomyosin-kinase receptors, to promote therapeutic neovascularization in animal models of hindlimb ischemia. Conversely, the neurotrophin low-affinity p75(NTR) receptor induces apoptosis of endothelial cells and vascular smooth muscle cells and impairs angiogenesis. Finally, nerve growth factor looks particularly promising in treating microvascular complications of diabetes or reducing cardiomyocyte apoptosis in the infarcted heart. These seminal discoveries have fuelled basic and translational research and thus opened a new field of investigation in cardiovascular medicine and therapeutics. Here, we review recent progress on the molecular signaling and roles played by neurotrophins in cardiovascular development, function, and pathology, and we discuss therapeutic potential of strategies based on neurotrophin manipulation.
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Affiliation(s)
- Andrea Caporali
- Division of Experimental Cardiovascular Medicine, University of Bristol, Bristol, UK
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191
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Eglen RM, Reisine T. The Current Status of Drug Discovery Against the Human Kinome. Assay Drug Dev Technol 2009; 7:22-43. [DOI: 10.1089/adt.2008.164] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Richard M. Eglen
- Bio-discovery, PerkinElmer Life and Analytical Sciences, Waltham, Massachusetts
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192
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Trypanosoma cruzi promotes neuronal and glial cell survival through the neurotrophic receptor TrkC. Infect Immun 2009; 77:1368-75. [PMID: 19179422 DOI: 10.1128/iai.01450-08] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Trypanosoma cruzi, the agent of Chagas' disease, promotes neuron survival through receptor tyrosine kinase TrkA and glycosylphosphatidylinositol-anchored glial cell-derived family ligand receptors (GFRalpha). However, these receptors are expressed by only a subset of neurons and at low levels or not at all in glial cells. Thus, T. cruzi might exploit an additional neurotrophic receptor(s) to maximize host-parasite equilibrium in the nervous system. We show here that T. cruzi binds TrkC, a neurotrophic receptor expressed by glial cells and many types of neurons, and that the binding is specifically inhibited by neurotrophin-3, the natural TrkC ligand. Coimmunoprecipitation and competition assays show that the trans-sialidase/parasite-derived neurotrophic factor (PDNF), previously identified as a TrkA ligand, mediates the T. cruzi-TrkC interaction. PDNF promotes TrkC-dependent mitogen-activated protein kinase signaling, neurite outgrowth, and survival of genetically engineered PC12 neuronal cells and glial Schwann cells in a TrkC-dependent manner. Thus, TrkC is a new neurotrophic receptor that T. cruzi engages to promote the survival of neuronal and glial cells. The results raise the possibility that T. cruzi recognition of TrkC underlies regenerative events in nervous tissues of patients with Chagas' disease.
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193
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Lombardi L, De Stefano ME, Paggi P. Components of the NGF signaling complex are altered in mdx mouse superior cervical ganglion and its target organs. Neurobiol Dis 2008; 32:402-11. [PMID: 18725298 DOI: 10.1016/j.nbd.2008.07.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 07/11/2008] [Accepted: 07/29/2008] [Indexed: 01/19/2023] Open
Abstract
We previously reported that in the superior cervical ganglion (SCG) of dystrophic mdx mice, which lack full-length dystrophin, there is a loss of neurons projecting to SCG muscular targets, like the iris. Nonetheless, surviving neurons, innervating either iris or submandibular gland (SuGl), a SCG non-muscular target, underwent reduced axon defasciculation and terminal branching. Here we report that, during early post-natal development, levels of pro-apoptotic proNGF in mdx mouse iris, but not in the SuGl, are higher than in the wild-type. This increase, along with reduced levels of NGF receptors (TrkA and p75NTR) in SCG, may be partly responsible for the observed loss of neurons projecting to the iris. These alterations, combined with a reduction in polysialylated-NCAM and neurofilament protein levels in SCG, may also account for reduced axon defasciculation and terminal branching in mdx mouse SCG targets.
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MESH Headings
- Animals
- Blotting, Western
- Dyneins/genetics
- Dyneins/metabolism
- Electrophoresis, Polyacrylamide Gel
- Enzyme-Linked Immunosorbent Assay
- Gene Expression
- Immunohistochemistry
- Iris/innervation
- Iris/metabolism
- Male
- Mice
- Mice, Inbred mdx
- Muscular Dystrophy, Animal/genetics
- Muscular Dystrophy, Animal/metabolism
- Nerve Growth Factor/biosynthesis
- Nerve Growth Factor/genetics
- Nerve Growth Factor/metabolism
- Neural Cell Adhesion Molecule L1/genetics
- Neural Cell Adhesion Molecule L1/metabolism
- Protein Precursors/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptor, trkA/biosynthesis
- Receptor, trkA/genetics
- Receptor, trkA/metabolism
- Receptors, Nerve Growth Factor/biosynthesis
- Receptors, Nerve Growth Factor/genetics
- Receptors, Nerve Growth Factor/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sialic Acids/genetics
- Sialic Acids/metabolism
- Signal Transduction
- Submandibular Gland/innervation
- Submandibular Gland/metabolism
- Superior Cervical Ganglion/metabolism
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Affiliation(s)
- Loredana Lombardi
- Dipartimento di Biologia Cellulare e dello Sviluppo, Sapienza Università di Roma, Italy
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194
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The protein phosphatase 2A regulatory subunits B'beta and B'delta mediate sustained TrkA neurotrophin receptor autophosphorylation and neuronal differentiation. Mol Cell Biol 2008; 29:662-74. [PMID: 19029245 DOI: 10.1128/mcb.01242-08] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nerve growth factor (NGF) is critical for the differentiation and maintenance of neurons in the peripheral and central nervous system. Sustained autophosphorylation of the TrkA receptor tyrosine kinase and long-lasting activation of downstream kinase cascades are hallmarks of NGF signaling, yet our knowledge of the molecular mechanisms underlying prolonged TrkA activity is incomplete. Protein phosphatase 2A (PP2A) is a heterotrimeric Ser/Thr phosphatase composed of a scaffolding, catalytic, and regulatory subunit (B, B', and B" gene families). Here, we employ a combination of pharmacological inhibitors, regulatory subunit overexpression, PP2A scaffold subunit exchange, and RNA interference to show that PP2A containing B' family regulatory subunits participates in sustained NGF signaling in PC12 cells. Specifically, two neuron-enriched regulatory subunits, B'beta and B'delta, recruit PP2A into a complex with TrkA to dephosphorylate the NGF receptor on Ser/Thr residues and to potentiate its intrinsic Tyr kinase activity. Acting at the receptor level, PP2A/ B'beta and B'delta enhance NGF (but not epidermal growth factor or fibroblast growth factor) signaling through the Akt and Ras-mitogen-activated protein kinase cascades and promote neuritogenesis and differentiation of PC12 cells. Thus, select PP2A heterotrimers oppose desensitization of the TrkA receptor tyrosine kinase, perhaps through dephosphorylation of inhibitory Ser/Thr phosphorylation sites on the receptor itself, to maintain neurotrophin-mediated developmental and survival signaling.
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195
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Induction of proneurotrophins and activation of p75NTR-mediated apoptosis via neurotrophin receptor-interacting factor in hippocampal neurons after seizures. J Neurosci 2008; 28:9870-9. [PMID: 18815271 DOI: 10.1523/jneurosci.2841-08.2008] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Seizure-induced damage elicits a loss of hippocampal neurons mediated to a great extent by the p75 neurotrophin receptor (NTR). Proneurotrophins, which are potent apoptosis-inducing ligands for p75(NTR), were increased in the hippocampus, particularly in astrocytes, by pilocarpine-induced seizures; and infusion of anti-pro-NGF dramatically attenuated neuronal loss after seizures. The p75(NTR) is expressed in many different cell types in the nervous system, and can mediate a variety of different cellular functions by recruiting specific intracellular binding proteins to activate distinct signaling pathways. In this study, we demonstrate that neurotrophin receptor-interacting factor (NRIF) mediates apoptotic signaling via p75(NTR) in hippocampal neurons in vitro and in vivo. After seizure-induced injury, NRIF(-/-) mice showed an increase in p75(NTR) expression in the hippocampus; however, these neurons failed to undergo apoptosis in contrast to wild-type mice. Treatment of cultured hippocampal neurons with proneurotrophins induced association of NRIF with p75(NTR) and subsequent translocation of NRIF to the nucleus, which was dependent on cleavage of the receptor. Neurons lacking NRIF were resistant to p75(NTR)-mediated apoptosis in vitro and in vivo. In addition, we demonstrate some mechanistic differences in p75(NTR) signaling in hippocampal neurons compared with other cell types. Overall, these studies demonstrate the requirement for NRIF to signal p75(NTR)-mediated apoptosis of hippocampal neurons and that blocking pro-NGF can inhibit neuronal loss after seizures.
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196
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Klinger MB, Vizzard MA. Role of p75NTR in female rat urinary bladder with cyclophosphamide-induced cystitis. Am J Physiol Renal Physiol 2008; 295:F1778-89. [PMID: 18842820 DOI: 10.1152/ajprenal.90501.2008] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Previous studies demonstrated changes in urinary bladder neurotrophin content and upregulation of neurotrophin receptors, TrkA and the p75 neurotrophin receptor (p75(NTR)), in micturition reflex pathways after cyclophosphamide (CYP)-induced cystitis. p75(NTR) can bind nerve growth factor (NGF) and modulate NGF-TrkA binding and signaling. We examined p75(NTR) expression and the role of p75(NTR) in the micturition reflex in control and CYP-treated rats. p75(NTR) Immunoreactivity was present throughout the urinary bladder. CYP-induced cystitis (4 h, 48 h, chronic) increased (P < or = 0.05) p75(NTR) expression in whole urinary bladder as shown by Western blotting. The role of p75(NTR) in bladder function in control and CYP-treated rats was determined using conscious cystometry and immunoneutralization or PD90780, a compound known to specifically block NGF binding to p75(NTR). An anti-p75(NTR) monoclonal antibody or PD90780 was infused intravesically and cystometric parameters were evaluated. Both methods of p75(NTR) blockade significantly (P < or = 0.05) decreased the intercontraction interval and void volume in control and CYP-treated rats. Intravesical infusion of PD90780 also significantly (P < or = 0.001) increased intravesical pressure and increased the number of nonvoiding contractions during the filling phase. Control intravesical infusions of isotype-matched IgG and vehicle were without effect. Intravesical instillation of PD90780 significantly (P < or = 0.01) reduced the volume threshold to elicit a micturition contraction in control rats (no inflammation) and CYP-treated in a closed urinary bladder system. These studies demonstrate 1) ubiquitous p75(NTR) expression in urinary bladder and increased expression with CYP-induced cystitis and 2) p75(NTR) blockade at the level of the urinary bladder produces bladder hyperreflexia in control and CYP-treated rats. The overall activity of the urinary bladder reflects the balance of NGF-p75(NTR) and NGF-TrkA signaling.
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Affiliation(s)
- Mary Beth Klinger
- Dept. of Neurology, Univ. of Vermont College of Medicine, D415A Given Research Bldg., Burlington, VT 05405, USA
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197
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Wong AW, Willingham M, Xiao J, Kilpatrick TJ, Murray SS. Neurotrophin receptor homolog-2 regulates nerve growth factor signaling. J Neurochem 2008; 106:1964-76. [PMID: 18624909 DOI: 10.1111/j.1471-4159.2008.05539.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The neurotrophin receptor homolog (NRH2) is closely related to the p75 neurotrophin receptor (p75NTR); however, its function and role in neurotrophin signaling are unclear. NRH2 does not bind to nerve growth factor (NGF), however, is able to form a receptor complex with tropomyosin-related kinase receptor A (TrkA) and to generate high-affinity NGF binding sites. Despite this, the mechanisms underpinning the interaction between NRH2 and TrkA remain unknown. Here, we identify that the intracellular domain of NRH2 is required to form an association with TrkA. Our data suggest extensive intracellular interaction between NRH2 and TrkA, as either the juxtamembrane or death domain regions of NRH2 are sufficient for interaction with TrkA. In addition, we demonstrate that TrkA signaling is dramatically influenced by the co-expression of NRH2. Importantly, NRH2 did not influence all downstream TrkA signaling pathways, but rather exerted a specific effect, enhancing src homology 2 domain-containing transforming protein (Shc) activation. Moreover, downstream of Shc, the co-expression of NRH2 resulted in TrkA specifically modulating mitogen-activated protein kinase pathway activation, but not the phosphatidylinositol 3-kinase/Akt pathway. These results indicate that NRH2 utilizes intracellular mechanisms to not only regulate NGF binding to TrkA, but also specifically modulate TrkA receptor signaling, thus adding further layers of complexity and specificity to neurotrophin signaling.
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Affiliation(s)
- Agnes W Wong
- Neurotrophin Signaling Laboratory, The Centre for Neuroscience, The University of Melbourne, Victoria, Australia
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198
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Gong Y, Cao P, Yu HJ, Jiang T. Crystal structure of the neurotrophin-3 and p75NTR symmetrical complex. Nature 2008; 454:789-93. [PMID: 18596692 DOI: 10.1038/nature07089] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 05/16/2008] [Indexed: 11/09/2022]
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199
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Covaceuszach S, Cassetta A, Konarev PV, Gonfloni S, Rudolph R, Svergun DI, Lamba D, Cattaneo A. Dissecting NGF interactions with TrkA and p75 receptors by structural and functional studies of an anti-NGF neutralizing antibody. J Mol Biol 2008; 381:881-96. [PMID: 18635195 DOI: 10.1016/j.jmb.2008.06.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 05/30/2008] [Accepted: 06/04/2008] [Indexed: 11/29/2022]
Abstract
The anti-nerve growth factor (NGF) monoclonal antibody alphaD11 is a potent antagonist that neutralizes the biological functions of its antigen in vivo. NGF antagonism is expected to be a highly effective and safe therapeutic approach in many pain states. A comprehensive functional and structural analysis of alphaD11 monoclonal antibody was carried out, showing its ability to neutralize NGF binding to either tropomyosine receptor kinase A (TrkA) or p75 receptors. The 3-D structure of the alphaD11 Fab fragment was solved at 1.7 A resolution. A computational docking model of the alphaD11 Fab-NGF complex, based on epitope mapping using a pool of 44 NGF mutants and experimentally validated by small-angle X-ray scattering, provided the structural basis for identifying the residues involved in alphaD11 Fab binding. The present study pinpoints loop II of NGF to be an important structural determinant for NGF biological activity mediated by TrkA receptor.
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200
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Abstract
Most of the previous work on the sphingolipid ceramide has been devoted to its function as an apoptosis inducer. Recent studies, however, have shown that in stem cells, ceramide has additional nonapoptotic functions. In this article, ceramide signaling will be reviewed in light of 'systems interface biology': as an interconnection of sphingolipid metabolism, membrane biophysics and cell signaling. The focus will be on the metabolic interconversion of ceramide and sphingomyelin or sphingosine-1-phosphate. Lipid rafts and sphingolipid-induced protein scaffolds will be discussed as a membrane interface for lipid-controlled cell signaling. Ceramide/sphingomyelin and ceramide/sphingosine-1-phosphate-interdependent cell-signaling pathways are significant for the regulation of cell polarity, apoptosis and/or proliferation, and as novel pharmacologic targets in cancer and stem cells.
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Affiliation(s)
- Erhard Bieberich
- Institute of Molecular Medicine & Genetics, School of Medicine, Medical College of Georgia, 1120 15th Street, Room CB-2803, Augusta, GA 30912, USA
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