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ABSTRACT: Nerve growth factor (NGF) is known to regulate the development and survival of select populations of neurons via its binding/activation of the TrkA and p75(NTR) receptors. However, in some physiological circumstances NGF dysregulation can result in debilitating pathologies, including diabetic neuropathies, interstitial cystitis and fibromyalgia. Thus, the identification of small molecules which inhibit NGF signalling have significant therapeutic potential. PD 90780, Ro 08-2750, and ALE 0540 are small molecules that have been reported to bind and inhibit NGF activity. Importantly, the docking site of these compounds is hypothesized to occur at the loop I/IV cleft of NGF - a region which is required for efficient and selective binding of this neurotrophin to its receptor(s). Molecular modeling predicts a number of previously reported NGF antagonists (PD 90780, ALE 0540, and Ro 08-2750) share conserved molecular features, and these drug-like small molecules have the ability to bind and modify the molecular topology of NGF. In order to understand the putative mechanism of binding, we synthesized a pyrazoloquinazolinecarboxilate analogue series and tested each compound in an NGF-dependent PC12 cell differentiation assay. In vitro data confirms that the pyrazoloquinazolinecarboxilate analogues functionally inhibit NGF's effects on PC12 cell differentiation. The results of this study provide evidence to refine the docking mode of pyrazoloquinazolinecarboxilate based compounds for the purposes of inhibiting NGF in vitro. In addition, we identified series analogue PQC 083 (IC50=7.0µM; CI=5.4-10.1µM) which displays markedly higher potency than previously described NGF antagonists.
European journal of pharmacology 03/2013; · 2.59 Impact Factor
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ABSTRACT: Nerve growth factor (NGF) is critical for the development and maintenance of sympathetic and sensory neurons in the developing nervous system, including nociceptors. In the adult nervous system, NGF is known to produce significant pain signals by binding to the TrkA and p75NTR receptors. Several pathological pain disorders are associated with nerve growth factor dysregulation, including neuropathic pain, osteoarthritic pain, and hyperalgesia. Currently, clinical management of these pathologies has relied on the use of opioid and non-steroidal anti-inflammatory drugs (NSAID). However, several chronic pain conditions demonstrate insensitivity to NSAID treatment or the development of detrimental opioid-related side effects, including addiction. As NGF plays an important role in pain generation; antibodies, small molecules and peptides have been designed to antagonize NGF. In this review, we discuss the structural biology of NGF ligand/receptor interaction, and we review current biological and pharmacological strategies to modulate NGF-related pathologies.
Neurochemistry International 10/2012; · 2.86 Impact Factor
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ABSTRACT: To investigate the beneficial properties associated with polyphenols, we screened 12 polyphenols for their ability to increase the viability of PC12 cells subjected to oxidative stress via CoCl2 and H2O2. Cell viability data demonstrate that 50 micromol/L methyl gallate and 50 micromol/L fisetin significantly increase viability of H2O2-stressed cells. Further, viability data suggest that 100 micromol/L epigallocatechin gallate (EGCG) increases basal viability, but has no rescue effect on cells stressed with CoCl2 or H2O2. Analysis of intracellular reactive oxygen species (ROS) shows that EGCG, methyl gallate, and gallic acid are effective in reducing CoCl2-derived ROS, and that methyl gallate is effective in attenuating H2O2-derived ROS. Examination of nitric oxide concentrations shows that methyl gallate significantly increases nitric oxide, both in nonstressed and H2O2-stressed cells, whereas EGCG results are consistent with the scavenging of nitric oxide under nonstressed and stressed conditions. Furthermore, analysis of total glutathione levels reveals that EGCG, methyl gallate, and gallic acid pretreatments with and without H2O2 stress have the ability to significantly alter glutathione metabolism. These findings suggest that EGCG, methyl gallate, and gallic acid may have potential therapeutic properties.
Canadian Journal of Physiology and Pharmacology 04/2010; 88(4):429-38. · 1.95 Impact Factor
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ABSTRACT: Clinically, Parkinson's disease (PD) is a neurodegenerative disorder characterized by the development of tremors and rigidity that is found primarily in patients over the age of 50. At the cellular level, it is clear that the pathology of PD results from the progressive loss of dopaminergic neurons in the substantia nigra. Several lines of evidence have implicated oxidative stress as a contributing factor to the depletion of dopaminergic neurons in PD. Under conditions of oxidative stress, the neurotransmitter dopamine can be oxidized to form neurotoxic quinone and semiquinone products. While dopaquinones are known to be extremely reactive towards sulfhydryl groups of many cellular substrates, mounting evidence suggests that their toxic effects can be quenched by intrinsic antioxidant mechanisms (e.g., glutathione). However, to respond appropriately to differing levels of oxidative stress, cells require a mechanism to regulate an appropriate response. This manuscript proposes metallothionein as a major cellular sensor of oxidized dopamine stress and metallothionein-mediated Zn2+ mobilization as an effecter signal that is used by the cell to manage oxidized dopamine as an intrinsic neurotoxin.
Canadian Journal of Physiology and Pharmacology 03/2010; 88(3):305-12. · 1.95 Impact Factor
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ABSTRACT: Neurodegenerative disorders are a class of diseases that have been linked to apoptosis induced by elevated levels of reactive oxygen species (ROS). ROS activates the apoptotic cascade through mitochondrial dysfunction and damage to lipids, proteins and DNA. Recently, fruit and tea-derived polyphenols have been found to be beneficial in decreasing oxidative stress and increasing overall health. Further, polyphenols including epigallocatechin gallate (EGCG) have been reported to inhibit apoptotic signaling and increase neural cell survival. In an effort to better understand the beneficial properties associated with polyphenol consumption, the aim of this study was to explore the neuroprotective effects of EGCG, methyl gallate (MG), gallic acid (GA) and N-acetylcysteine (NAC) on H(2)O(2)-induced apoptosis in PC12 cells and elucidate potential protective mechanisms. Cell viability data demonstrates that MG and NAC pre-treatments significantly increase viability of H(2)O(2)-stressed cells, while pre-treatments with EGCG and GA exacerbates stress. Quantitation of apoptosis and mitochondrial membrane potential shows that MG pre-treatment prevents mitochondria depolarization, however does not inhibit apoptosis and is thus evidence that MG can inhibit mitochondria-mediated apoptosis. Subsequent analysis of DNA degradation and caspase activation reveals that MG inhibits activation of caspase 9 and has a partial inhibitory effect on DNA degradation. These findings confirm the involvement of both intrinsic and extrinsic apoptotic pathways in H(2)O(2)-induced apoptosis and suggest that MG may have potential therapeutic properties against mitochondria-mediated apoptosis.
Biochemical and Biophysical Research Communications 02/2010; 393(4):773-8. · 2.48 Impact Factor
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ABSTRACT: Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are members of the neurotrophin family that normally play a role in the development and maintenance of the nervous system. However, neurotrophin dysregulation has been implicated in several neurodegenerative diseases and psychiatric disorders including Alzheimer's disease, Parkinson's disease, neuropathic pain, depression, and substance abuse. Despite their central role in the nervous system, neurotrophins have proved to be an elusive pharmacological target. Here, we describe a novel multipotent neurotrophin antagonist, 3-[(5E)-4-oxo-5-[[5-(4-sulfamoylphenyl)-2-furyl]methylene]-2-thioxo-thiazolidin-3-yl]propanoic acid (Y1036). Y1036 binds BDNF (K(D) = 3.5 +/- 0.3 microM) and NGF (K(D) = 3.0 +/- 0.4 microM) preventing either BDNF or NGF from interacting with their obligate receptor(s). Y1036 prevents both BDNF- and NGF-mediated trk activation, downstream activation of the p44/42 mitogen-activated protein kinase pathway, and neurotrophin-mediated differentiation of dorsal-root ganglion sensory neurons. Identification of a BDNF- and NGF-specific antagonist is of considerable interest in the study and treatment of diseases where dysregulation of multiple neurotrophins has been implicated.
Journal of Pharmacology and Experimental Therapeutics 11/2009; 332(2):446-54. · 3.83 Impact Factor
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ABSTRACT: Alpha-synuclein protein aggregates are a major component of Lewy bodies, the intracytoplasmic inclusions found in dopaminergic neurons that are a defining characteristic of Parkinson's disease. Other "synucleopathies" include dementia with Lewy bodies and multisystem atrophy. In vitro, the formation of these deposits can be induced by a number of substances, including metal ions. Fish provide a useful model to study the long-term biological effects of metal ion exposure, but to date no studies have been reported concerning such exposures with respect to alpha-synuclein aggregation. Mature white sucker fish (Catostomus commersoni; aged 5-8 years) were sampled from two sites within the Red Lake area of Northwestern Ontario, a region highly contaminated by metal ions due to mining activity. Individual fish were characterized with respect to liver metal ion uptake and metallothionein levels. Central nervous system (CNS) tissues of fish from test sites representing high and low metal ion contamination were examined immunohistochemically using a polyclonal antibody recognising alpha-synuclein protein. We demonstrate here that the CNS of fish exposed to elevated metal ion environments had increased alpha-synuclein-like immunoreactive aggregates, potentially reflecting metal ion exposure leading to CNS toxicity. These findings demonstrate that fish may be an important new model for studying environmental risk factors and the pathology associated with Parkinson's disease.
Aquatic toxicology (Amsterdam, Netherlands) 03/2009; 92(4):258-63. · 3.12 Impact Factor
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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+).
Environmental Toxicology and Pharmacology 03/2009; 27(2):298-302. · 1.47 Impact Factor
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ABSTRACT: Trypanosome trans-sialidase (TS) is a sialic acid-transferring enzyme that hydrolyzes alpha2,3-linked sialic acids and transfers them to acceptor molecules. Here we show that a highly purified recombinant TS derived from T. cruzi parasites targets TrkA receptors on TrkA-expressing PC12 cells and colocalizes with TrkA internalization and phosphorylation (pTrkA). Maackia amurensis lectin II (MAL-II) and Sambucus nigra lectin (SNA) block TS binding to TrkA-PC12 cells in a dose-dependent manner with subsequent inhibition of TS colocalization with pTrkA. Cells treated with lectins alone do not express pTrkA. The catalytically inactive mutant TSDeltaAsp98-Glu also binds to TrkA-expressing cells, but is unable to induce pTrkA. TrkA-PC12 cells treated with a purified recombinant alpha2,3-neuraminidase (Streptococcus pneumoniae) express pTrkA. Wild-type TS but not the mutant TSDeltaAsp98-Glu promotes neurite outgrowth in TrkA-expressing PC12 cells. In contrast, these effects are not observed in TrkA deficient PC12nnr5 cells but are reestablished in PC12nnr5 cells stably transfected with TrkA and are significantly blocked by inhibitors of tyrosine kinase (K-252a) and MAP/MEK protein kinase (PD98059). Together these observations suggest for the first time that hydrolysis of sialyl alpha2,3-linked beta-galactosyl residues of TrkA receptors plays an important role in TrkA receptor activation, sufficient to promote cell differentiation (neurite outgrowth) independent of nerve growth factor.
Glycobiology 12/2004; 14(11):987-98. · 3.58 Impact Factor
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ABSTRACT: The nucleus accumbens (NAc) plays a role in conditioned place preference (CPP). The authors tested the hypothesis that inhibition of mitogen-activated protein kinases (MAPKs) would inhibit NAc-amphetamine-produced CPP. Results confirmed that NAc amphetamine increased levels of the MAPK extracellular signal-regulated kinase (ERK). In CPP studies, NAc injections (0.5 microl per side) of the ERK inhibitor PD98059 (1.0-2.5 microg) or the p38 kinase inhibitor SB203580 (15-500 ng) dose dependently impaired CPP. The c-Jun-N-terminal kinase (JNK) inhibitor SP600125 (1.0-2.5 microg) failed to block the CPP effect. The drugs did not block amphetamine-induced motor activity. Results suggest that ERK and p38, but not JNK, MAPKs may be necessary for the establishment of NAc amphetamine-produced CPP and may also mediate other forms of reward-related learning dependent on NAc.
Behavioral Neuroscience 09/2004; 118(4):740-50. · 2.62 Impact Factor
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ABSTRACT: The neurotrophin nerve growth factor (NGF) binds to two receptor types: the tyrosine kinase receptor TrkA and the common neurotrophin receptor p75(NTR). Although many of the biological effects of NGF (such as neuronal growth and survival) are associated with TrkA activation, p75(NTR) also contributes to these activities by enhancing the action of TrkA when receptors are coexpressed. The NGF antagonist PD90780 [7-(benzolylamino)-4,9-dihydro-4-methyl-9-oxo-pyrazolo[5,1-b]quinazoline-2-carboxylic acid] interacts with NGF, preventing its binding to p75(NTR). In this study, the actions of this compound are further explored, and it is found that PD90780 is not able to inhibit the binding of either brain-derived neurotrophic factor or neurotrophin-3 to p75(NTR), consistent with the direct interactions of the antagonist with NGF. In addition, we demonstrate that the ability of PD90780 to inhibit NGF-p75(NTR) interactions is lower when receptors are coexpressed, compared with when p75(NTR) is the only neurotrophin receptor expressed. These results suggest that the interaction between NGF and the p75(NTR) receptor is altered when TrkA is coexpressed. This alteration can be exploited in the development of antagonists that will selectively inhibit the pro-apoptotic actions of p75(NTR) when expressed in the absence of TrkA, although having less effect on the pro-survival effects of p75(NTR) mediated by enhanced TrkA activation.
Journal of Pharmacology and Experimental Therapeutics 09/2004; 310(2):505-11. · 3.83 Impact Factor
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ABSTRACT: The ability of dopamine to induce apoptosis in a variety of cell types, including PC12 cells and neurons, has been well documented. Under non-reducing conditions, dopamine can be oxidized to semi-quinone and quinone species, which have the ability to arylate proteins and lead to the formation of covalent adducts. Potentially, it is the arylation of substrates critical to cell survival and/or the formation of toxic adducts which leads to the death observed after dopamine treatment. We have previously described the ability of a substituted monohydroxy-tetra-hydronaphthalene (DATN) to bind proteins that are susceptible to arylation by dopamine and related catecholamines. As DATN can prevent the covalent incorporation of dopamine into substrate molecules, we hypothesized that this compound could have a protective effect on cells that undergo apoptotic death in response to dopamine exposure. We report here that DATN prevents the dopamine-induced apoptotic death of PC12 cells in a dose-dependent manner. DATN did not prevent the oxidative stress associated with dopamine treatment, as lipid peroxide production was not influenced by DATN treatment. The ability of DATN to prevent dopamine-induced cell death was selective for this insult, as this compound did not influence the death of PC12 cells induced by hydrogen peroxide (H(2)O(2)). Consistent with this finding, DATN did not alter lipid peroxidation, nor oxidation of intracellular dichlorodihydrofluorescein subsequent to H(2)O(2) treatment. Consistent with a reduction in apoptotic death, the increase in caspase-3 activity associated with dopamine treatment was also prevented by DATN. These observations suggest that DATN may act to prevent one of the pathways linking dopamine and oxidative stress to caspase-3 activation. We propose that the inhibition of substrate arylation by the products of dopamine oxidation may provide a useful strategy for the prevention of dopamine-induced cell death.
Neuropharmacology 07/2004; 46(7):984-93. · 4.81 Impact Factor
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ABSTRACT: Nerve growth factor (NGF) promotes neuronal survival and differentiation and stimulates neurite outgrowth. NGF is synthesized as a precursor, proNGF, which undergoes post-translational processing to generate mature beta-NGF. It has been assumed that, in vivo, NGF is largely processed into the mature form and that mature NGF accounts for the biological activity. However, we recently showed that proNGF is abundant in CNS tissues whereas mature NGF is undetectable, suggesting that proNGF has biological functions beyond its role as a precursor. To determine whether proNGF exhibits biological activity, we mutagenized the precursor-processing site and expressed unprocessed, cleavage-resistant proNGF protein in insect cells. Survival and neurite outgrowth assays on murine superior cervical ganglion neurons and PC12 cells indicated that proNGF exhibits neurotrophic activity similar to mature 2.5S NGF, but is approximately fivefold less active. ProNGF binds to the high-affinity receptor, TrkA, as determined by cross-linking to PC12 cells, and is also slightly less active than mature NGF in promoting phosphorylation of TrkA and its downstream signaling effectors, Erk1/2, in PC12 and NIH3T3-TrkA cells. These data, coupled with our previous report that proNGF is the major form of NGF in the CNS, suggest that proNGF could be responsible for much of the biological activity normally attributed to mature NGF in vivo.
Journal of Neurochemistry 06/2004; 89(3):581-92. · 4.06 Impact Factor
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ABSTRACT: This study examined the effects of hypomorphic p75 neurotrophin receptor (p75NTR) expression and high levels of nerve growth factor (NGF) on trkA phosphorylation and downstream activation of p44/42 mitogen-activated protein kinase (MAPK). Post-ganglionic sympathetic neurons from postnatal day 1 p75NTR exon III null mutant (p75(-/-)) and 129/SvJ mice were cultured in the presence of 50 ng/mL NGF and analysed by Western blotting. Levels of phosphorylated trkA are increased in p75(-/-) neurons compared with 129/SvJ neurons, and these higher levels are maintained with continuous exposure to NGF. MAPK is also phosphorylated to a greater extent in p75(-/-) neurons than in 129/SvJ neurons, both within 10 min of exposure to NGF, and with continuous NGF treatment for 5 days. These data provide new insight into the mechanism underlying enhanced neurite outgrowth in p75(-/-) neurons, demonstrating that trkA and MAPK signalling in sympathetic neurons are increased when p75NTR function is disrupted.
European Journal of Neuroscience 06/2004; 19(10):2903-8. · 3.63 Impact Factor
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ABSTRACT: Genetic, neurochemical, and environmental factors have been implicated in neurodegenerative disease, and a combination of these factors is likely responsible for disease onset and progression. Environmental toxicants implicated in Parkinson's disease include organic compounds, reactive oxygen species, metal ions and others. Exposure to a combination of environmental toxicants may produce a synergistic insult leading to neuronal death, even though levels of individual toxicants may be below detection by conventional methods. Rodent models of toxicant-induced neurodegeneration are hampered by the high resistance of these animals to many environmental toxicants. Extensive literature on aquatic toxicology and the high homology between many human and fish neurotrophic factors makefish a useful model for investigating environmental toxicants and neurodegeneration. Skin color in salmonids is under catecholaminergic control; pigment-containing melanophores aggregate when stimulated, resulting in paling. We demonstrate that lesions to nerves innervating melanophores prevent aggregation and produce dark skin color. The time course for return of skin color corresponds to neuronal regeneration, a neurotrophin-dependent event. Observations from this model system may be useful for predicting risks associated with environmental toxicants and nervous system integrity, and may have important implications for the identification of risk factors.
NeuroToxicology 11/2002; 23(4-5):545-51. · 3.10 Impact Factor
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ABSTRACT: Neurotrophins are a family of proteins with pleiotropic effects mediated by two distinct receptor types, namely the trk family
and the common neurotrophin receptor p75NTR Binding of four mammalian neurotrophins, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3
(NT-3) and neurotrophin-4/5 (NT-4/5), to p75NTR is studied by large scale molecular dynamics simulations using CHARMM force field. Geometric match of neurotrophin/receptor
binding domains in the complexes is evaluated by the Lawrence & Colman’s shape complementarity statistic Sc. The model of neurotrophin/receptor interactions suggests that the receptor binding domains of neurotrophins (loops I and
IV) are geometrically and electrostatically complementary to a putative binding site of p75NTR formed by the second and part of the third cysteine-rich domains. All charged residues within the loops I and IV of the neurotrophins,
previously determined as being critical for p75NTR binding, directly participate in receptor binding in the framework of the model. Principal residues of the binding site of
p75NTR include Asp47, Lys56, Asp75, Asp76, Asp88 and Glu89. The additional involvement of Arg80 and Glu73 is specific for NGF and BDNF, respectively, and Glu73 participates in binding with NT-3 and NT-4/5. The model developed has utility in computer-aided molecular design.
12/2001: pages 99-113;
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ABSTRACT: It has recently been shown that transition metal cations Zn2+ and Cu2+ bind to histidine residues of nerve growth factor (NGF) and other neurotrophins (a family of proteins important for neuronal survival) leading to their inactivation. Experimental data and theoretical considerations indicate that transition metal cations may destabilize the ionic form of histidine residues within proteins, thereby decreasing their pKa values. Because the release of transition metal cations and acidification of the local environment represent important events associated with brain injury, the ability of Zn2+ and Cu2+ to bind to neurotrophins in acidic conditions may alter neuronal death following stroke or as a result of traumatic injury. To test the hypothesis that metal ion binding to neurotrophins is influenced by pH, the effects of Zn2+ and Cu2+ on NGF conformation, receptor binding and NGF tyrosine kinase (trkA) receptor signal transduction were examined under conditions mimicking cerebral acidosis (pH range 5.5–7.4). The inhibitory effect of Zn2+ on biological activities of NGF is lost under acidic conditions. Conversely, the binding of Cu2+ to NGF is relatively independent of pH changes within the studied range. These data demonstrate that Cu2+ has greater binding affinity to NGF than Zn2+ at reduced pH, consistent with the higher affinity of Cu2+ for histidine residues. These findings suggest that cerebral acidosis associated with stroke or traumatic brain injury could neutralize the Zn2+-mediated inactivation of NGF, whereas corresponding pH changes would have little or no influence on the inhibitory effects of Cu2+. The importance of His84 of NGF for transition metal cation binding is demonstrated, confirming the involvement of this residue in metal ion coordination.
Journal of Neurochemistry 12/2001; 78(3):515 - 523. · 4.06 Impact Factor
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ABSTRACT: Oxidative stress is considered to be a major contributor to dysfunction in a host of disease states. Reactive oxygen species (ROS) mediate distinct oxidative alterations in biopolymers, including DNA, proteins, lipids, and lipoproteins. Currently, the mechanisms of biochemical reactions underlying oxidative stress are poorly understood because of the instability of ROS. One of the consequences of oxidative stress is one-electron oxidation of tyrosine (Tyr) residues in proteins, which represents a hallmark of this insult and is implicated in the pathogenesis of a number of pathological processes leading to atherosclerosis, inflammatory conditions, multiple system atrophy and several neurodegenerative diseases. Major products of oxidation of Tyr include protein-bound dityrosine and isodityrosine. In this report, the mechanism of tyrosine coupling (including structure and stability of a number of proposed reaction intermediates) is studied by high-level density functional and conventional ab initio methods including B3LYP, MP2, CASSCF, and CASPT2. It is demonstrated that dityrosine and isodityrosine are the most stable structures at all theoretical levels applied. In addition to classical structures of the reaction intermediates, evidence is found for a novel transient structure of Tyr dimer, stacked dityrosyl. This dimer is predicted to exist because of strong electron correlation between two tyrosyl moieties. The counterpoise corrected energy of stacked dityrosyl is below the energy of two tyrosyl radicals by about 95 kJ/mol at the PUMP2/6-31G** level. High proton affinity of tyrosyl radical (about 9.4 eV) suggests that positively charged amino acids in the vicinity of a solvent-exposed Tyr residue may increase the probability of tyrosine coupling.
01/2001;
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ABSTRACT: Direct effects of Zn2+ on the conformation and biological activity of nerve growth factor (NGF) have previously been described. Zn2+ binds to specific coordination sites within NGF and induces conformational changes within domains that participate in receptor
recognition processes. Recent theoretical considerations indicate that other transition metal cations (particularly, Cu2+and Pd2+) are capable of forming similar complexes with NGF. Inactivation of NGF by transition metal cations is inhibitory to neuronal
regeneration and sprouting, and can lead to cell death under conditions where NGF is required for survival in PC12 cells.
In this study we investigated the influence of various metal ions on NGF conformation, geometry of NGF amino terminal peptide
and NGF-mediated biological effects in FC12 cells. A number of metal ions (Zn2+, Cu2+ and Pd2+) alter NGF conformation in cell-free assays and inhibit NGF-mediated cell survival. Other metals have been shown to be either
toxic to PC12 cells by mechanisms independent of NGF activity (e.g. Ag+, Hg2+) or non-toxic to the cells under conditions tested (e.g. Al3+, Cr3+). In conclusion, several metal cations are capable of inhibiting NGF activity, thereby blocking NGF-mediated cell survival
and plasticity.
Neurotoxicity Research 11/2000; 2(4):321-341. · 3.51 Impact Factor
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ABSTRACT: Right-handed twisting is a fundamental structural feature of β-pleated sheets in globular proteins which is critical for their geometry and function. The origin of this twisting is poorly understood and has represented a challenge for theoretical chemistry for almost 30 years. Density functional theory using the B3LYP exchange-correlation functional and the split-valence 6-31G** basis set has been utilized to investigate the structure and conformational transitions of single and double-stranded antiparallel β-sheet models to determine the driving force for the right-handed twisting. Right-handed twisting is found to be an intrinsic property of a peptide main chain because of the difference in rotational potentials around N(sp2)−Cα(sp3) and C(sp2)−Cα(sp3) bonds. The difference arises from a tendency of the single Cα(sp3)−C(sp2) bonds to eclipse the lone pair of atoms N(sp2), which results in decreasing absolute values of dihedral angles φ but not ψ. This tendency is suppressed by hydrogen bonding between adjacent CO and NH groups within single β-strands, and released only when these bonds are disrupted by the interstrand CO···HN hydrogen bonding. The results obtained constitute the following paradigm of the origin of β-sheet twist: although right-handed twisting of β-sheets in globular proteins is an inherent property of the peptide backbone within single β-strands, it is unleashed by the interstrand hydrogen bonding in multistranded β-sheets. The observed pleating, right-handed twisting, skewed mutual orientation of β-strands, and intrinsic conformational variability of double-stranded antiparallel β-sheet motifs in globular proteins are explained from the first principles.
10/2000;
