Lothar Gremer - Academia.edu (original) (raw)
Papers by Lothar Gremer
PloS one, 2016
Amyloid deposits formed from islet amyloid polypeptide (IAPP) are a hallmark of type 2 diabetes m... more Amyloid deposits formed from islet amyloid polypeptide (IAPP) are a hallmark of type 2 diabetes mellitus and are known to be cytotoxic to pancreatic β-cells. The molecular structure of the fibrillar form of IAPP is subject of intense research, and to date, different models exist. We present results of solid-state NMR experiments on fibrils of recombinantly expressed and uniformly 13C, 15N-labeled human IAPP in the non-amidated, free acid form. Complete sequential resonance assignments and resulting constraints on secondary structure are shown. A single set of chemical shifts is found for most residues, which is indicative of a high degree of homogeneity. The core region comprises three to four β-sheets. We find that the central 23-FGAILS-28 segment, which is of critical importance for amyloid formation, is part of the core region and forms a β-strand in our sample preparation. The eight N-terminal amino acid residues of IAPP, forming a ring-like structure due to a disulfide bridge b...
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Scientific reports, Jan 19, 2016
In type 2 diabetes, the formation of islet amyloid consisting of islet amyloid polypeptide (IAPP)... more In type 2 diabetes, the formation of islet amyloid consisting of islet amyloid polypeptide (IAPP) is associated with reduction in β-cell mass and contributes to the failure of islet cell transplantation. Rational design of inhibitors of IAPP amyloid formation has therapeutic potential, but is hampered by the lack of structural information on inhibitor complexes of the conformationally flexible, aggregation-prone IAPP. Here we characterize a β-hairpin conformation of IAPP in complex with the engineered binding protein β-wrapin HI18. The β-strands correspond to two amyloidogenic motifs, 12-LANFLVH-18 and 22-NFGAILS-28, which are connected by a turn established around Ser-20. Besides backbone hydrogen bonding, the IAPP:HI18 interaction surface is dominated by non-polar contacts involving hydrophobic side chains of the IAPP β-strands. Apart from monomers, HI18 binds oligomers and fibrils and inhibits IAPP aggregation and toxicity at low substoichiometric concentrations. The IAPP β-hairp...
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Biophysical journal, Jan 25, 2017
Pyroglutamate-modified amyloid-β (pEAβ) has been described as a relevant Aβ species in Alzheimer&... more Pyroglutamate-modified amyloid-β (pEAβ) has been described as a relevant Aβ species in Alzheimer's-disease-affected brains, with pEAβ (3-42) as a dominant isoform. Aβ (1-40) and Aβ (1-42) have been well characterized under various solution conditions, including aqueous solutions containing trifluoroethanol (TFE). To characterize structural properties of pEAβ (3-42) possibly underlying its drastically increased aggregation propensity compared to Aβ (1-42), we started our studies in various TFE-water mixtures and found striking differences between the two Aβ species. Soluble pEAβ (3-42) has an increased tendency to form β-sheet-rich structures compared to Aβ (1-42), as indicated by circular dichroism spectroscopy data. Kinetic assays monitored by thioflavin-T show drastically accelerated aggregation leading to large fibrils visualized by electron microscopy of pEAβ (3-42) in contrast to Aβ (1-42). NMR spectroscopy was performed for backbone and side-chain chemical-shift assignment...
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European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences, Jan 30, 2017
The aggregation of the amyloid β protein (Aβ) plays an important role in the pathology of Alzheim... more The aggregation of the amyloid β protein (Aβ) plays an important role in the pathology of Alzheimer's disease. Previously, we have developed the all-d-enantiomeric peptide D3, which is able to eliminate neurotoxic Aβ oligomers in vitro and improve cognition in a transgenic Alzheimer's disease mouse model in vivo even after oral administration. d-Peptides are expected to be more resistant against enzymatic proteolysis compared to their l-enantiomeric equivalents, and indeed, a pharmacokinetic study with tritiated D3 revealed the oral bioavailability to be about 58%. To further investigate the underlying properties, we examined the stability of D3 in comparison to its corresponding all-l-enantiomeric mirror image l-D3 in media simulating the gastrointestinal tract, blood and liver. Potential metabolization was followed by reversed-phase high-performance liquid chromatography. In simulated gastric fluid, D3 remained almost completely stable (89%) within 24h, while 70% of l-D3 w...
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ACS chemical neuroscience, Jan 5, 2017
Amyloid-beta (Aβ) oligomers are thought to be causative for the development and progression of Al... more Amyloid-beta (Aβ) oligomers are thought to be causative for the development and progression of Alzheimer's disease (AD). Starting from the Aβ oligomer eliminating D-enantiomeric peptide D3, we developed and applied a two-step procedure based on peptide microarrays to identify D3 derivatives with increased binding affinity and specificity for monomeric Aβ(1-42) to further enhance the Aβ oligomer elimination efficacy. Out of more than 1,000 D3 derivatives, we selected seven novel D-peptides, named ANK1 to ANK7, and characterized them in more detail in vitro. All ANK peptides bound to monomeric Aβ(1-42), eliminated Aβ(1-42) oligomers, inhibited Aβ(1-42) fibril formation, and reduced Aβ(1-42)-induced cytotoxicity more efficiently than D3. Additionally, ANK6 completely inhibited the prion-like propagation of pre-formed Aβ(1-42) seeds and showed a non-significant tendency for improving memory performance of tg-APPSwDI mice after i.p. application for 4 weeks. This supports the hypothes...
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The Journal of biological chemistry, Jan 16, 2016
IQ motif-containing GTPase activating protein 1 (IQGAP1) plays a central role in the physical ass... more IQ motif-containing GTPase activating protein 1 (IQGAP1) plays a central role in the physical assembly of relevant signaling networks that are responsible for various cellular processes, including cell adhesion, polarity, and transmigration. The RHO family proteins CDC42 and RAC1 have been shown to mainly interact with the GAP-related domain (GRD) of IQGAP1. However, the role of its RASGAP C-terminal (RGCT) and C-terminal domains in the interactions with RHO proteins has remained obscure. Here, we demonstrate that IQGAP1 interactions with RHO proteins underlie a multiple-step binding mechanism: (i) a high affinity, GTP-dependent binding of RGCT to the switch regions of CDC42 or RAC1 and (ii) a very low affinity binding of GRD and a C terminus adjacent to the switch regions. These data were confirmed by phosphomimetic mutation of serine 1443 to glutamate within RGCT, which led to a significant reduction of IQGAP1 affinity for CDC42 and RAC1, clearly disclosing the critical role of RG...
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Biochemistry, 2016
The interaction of the amyloid-β protein (Aβ) with neuronal cell membranes plays a crucial role i... more The interaction of the amyloid-β protein (Aβ) with neuronal cell membranes plays a crucial role in Alzheimer's disease. Aβ undergoes structural changes upon binding to ganglioside GM1 containing membranes leading to altered molecular characteristics of the protein. The physiological role of the Aβ interaction with the ganglioside GM1 is still unclear. In order to further elucidate the molecular requirements of Aβ membrane binding, we tested different nanodiscs varying in their lipid composition, regarding the charge of the headgroups as well as ganglioside GM1 concentration. Nanodiscs are excellent model membrane systems for studying protein membrane interactions, and we show here their suitability to investigate the membrane interaction of Aβ. In particular, we set out to investigate whether the binding activity of GM1 to Aβ is specific for the assembly state of Aβ and compared the binding affinities of monomeric with oligomeric Aβ. Using fluorescence titration experiments, we demonstrate high-affinity binding of Aβ(1-40) to GM1 containing nanodiscs, with dissociation constants, KD, in the range from 25 to 41 nM, in a GM1 concentration-dependent manner. Biolayer interferometry experiments confirmed the high-affinity binding of monomeric Aβ(1-40) (KD of 24 nM to 49 nM) as well as of Aβ(1-42) (KD of 30 nM) to GM1 containing nanodiscs, and no binding to phospholipid containing nanodiscs. Interestingly, and in contrast to monomeric Aβ, neither oligomeric Aβ(1-40) nor oligomeric Aβ(1-42) binds to GM1 nanodiscs. To the best of our knowledge, this is the first report of a loss of function for monomeric Aβ upon aggregation.
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PLOS ONE, 2016
[This corrects the article DOI: 10.1371/journal.pone.0147470.].
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J Mol Biol, 2000
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Biochemistry Usa, Feb 1, 2003
The structurally characterized molybdoenzyme carbon monoxide dehydrogenase (CODH) catalyzes the o... more The structurally characterized molybdoenzyme carbon monoxide dehydrogenase (CODH) catalyzes the oxidation of CO to CO2 in the aerobic bacterium Oligotropha carboxidovorans. The active site of the enzyme was studied by Mo- and Cu-K-edge X-ray absorption spectroscopy. This revealed a bimetallic [Cu(I)SMo(VI)(double bond O)2] cluster in oxidized CODH which was converted into a [Cu(I)SMo(IV)(double bond O)OH2] cluster upon reduction. The Cu...Mo distance is 3.70 A in the oxidized form and is increased to 4.23 A upon reduction. The bacteria contain CODH species with the complete and functional bimetallic cluster along with enzyme species deficient in Cu and/or bridging S. The latter are precursors in the posttranslational biosynthesis of the metal cluster. Cu-deficient CODH is the most prominent precursor and contains a [HSMo(double bond O)OH2] cluster. Se-K-edge X-ray absorption spectroscopy demonstrates that Se is coordinated by two C atoms at 1.94-1.95 A distance. This is interpreted as a replacement of the S in methionine residues. In contrast to a previous report [Dobbek, H., Gremer, L., Meyer, O., and Huber, R. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 8884-8889] Se was not identified in the active site of CODH.
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ACS chemical neuroscience, Jan 9, 2016
Alzheimer's disease (AD) is a neurodegenerative disorder and the most common type of dementia... more Alzheimer's disease (AD) is a neurodegenerative disorder and the most common type of dementia. Until now, there is no curative therapy available. Previously, we selected the amyloid-beta (Aβ) targeting peptide D3 consisting of 12 d-enantiomeric amino acid residues by mirror image phage display as a potential drug candidate for the treatment of AD. In the current approach, we investigated the optimization potential of linear D3 with free C-terminus (D3COOH) by chemical modifications. First, the impact of the net charge was investigated and second, cyclization was introduced which is a well-known tool for the optimization of peptides for enhanced target affinity. Following this strategy, three D3 derivatives in addition to D3COOH were designed: C-terminally amidated linear D3 (D3CONH2), cyclic D3 (cD3), and cyclic D3 with an additional arginine residue (cD3r) to maintain the net charge of linear D3CONH2. These four compounds were compared to each other according to their binding a...
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Science signaling, Jan 24, 2016
Cerebral amyloid angiopathy (CAA) is a vascular dysfunction disorder characterized by deposits of... more Cerebral amyloid angiopathy (CAA) is a vascular dysfunction disorder characterized by deposits of amyloid-β (Aβ) in the walls of cerebral vessels. CAA and Aβ deposition in the brain parenchyma contribute to dementia and Alzheimer's disease (AD). We investigated the contribution of platelets, which accumulate at vascular Aβ deposits, to CAA. We found that synthetic monomeric Aβ40 bound through its RHDS (Arg-His-Asp-Ser) sequence to integrin αIIbβ3, which is the receptor for the extracellular matrix protein fibrinogen, and stimulated the secretion of adenosine diphosphate (ADP) and the chaperone protein clusterin from platelets. Clusterin promoted the formation of fibrillar Aβ aggregates, and ADP acted through its receptors P2Y1 and P2Y12 on platelets to enhance integrin αIIbβ3 activation, further increasing the secretion of clusterin and Aβ40 binding to platelets. Platelets from patients with Glanzmann's thrombasthenia, a bleeding disorder in which platelets have little or dy...
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PLOS ONE, 2016
The aggregation of amyloid-β (Aβ) is postulated to be the crucial event in Alzheimer&... more The aggregation of amyloid-β (Aβ) is postulated to be the crucial event in Alzheimer's disease (AD). In particular, small neurotoxic Aβ oligomers are considered to be responsible for the development and progression of AD. Therefore, elimination of thesis oligomers represents a potential causal therapy of AD. Starting from the well-characterized d-enantiomeric peptide D3, we identified D3 derivatives that bind monomeric Aβ. The underlying hypothesis is that ligands bind monomeric Aβ and stabilize these species within the various equilibria with Aβ assemblies, leading ultimately to the elimination of Aβ oligomers. One of the hereby identified d-peptides, DB3, and a head-to-tail tandem of DB3, DB3DB3, were studied in detail. Both peptides were found to: (i) inhibit the formation of Thioflavin T-positive fibrils; (ii) bind to Aβ monomers with micromolar affinities; (iii) eliminate Aβ oligomers; (iv) reduce Aβ-induced cytotoxicity; and (v) disassemble preformed Aβ aggregates. The beneficial effects of DB3 were improved by DB3DB3, which showed highly enhanced efficacy. Our approach yielded Aβ monomer-stabilizing ligands that can be investigated as a suitable therapeutic strategy against AD.
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PLOS ONE, 2016
Alzheimer´s disease is the most prominent type of dementia and currently no causative treatment i... more Alzheimer´s disease is the most prominent type of dementia and currently no causative treatment is available. According to recent studies, oligomeric species of the amyloid beta (Aβ) peptide appear to be the most toxic Aβ assemblies. Aβ monomers, however, may be not toxic per se and may even have a neuroprotective role. Here we describe a competitive mirror image phage display procedure that allowed us to identify preferentially Aβ1-42 monomer binding and thereby stabilizing peptides, which destabilize and thereby eliminate toxic oligomer species. One of the peptides, called Mosd1 (monomer specific d-peptide 1), was characterized in more detail. Mosd1 abolished oligomers from a mixture of Aβ1-42 species, reduced Aβ1-42 toxicity in cell culture, and restored the physiological phenotype in neuronal cells stably transfected with the gene coding for human amyloid precursor protein.
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PloS one, 2015
A hallmark of Alzheimer's disease (AD) is the accumulation of extracellular amyloid-β (Aβ) pl... more A hallmark of Alzheimer's disease (AD) is the accumulation of extracellular amyloid-β (Aβ) plaques in the brains of patients. N-terminally truncated pyroglutamate-modified Aβ (pEAβ) has been described as a major compound of Aβ species in senile plaques. pEAβ is more resistant to degradation, shows higher toxicity and has increased aggregation propensity and β-sheet stabilization compared to non-modified Aβ. Here we characterized recombinant pEAβ(3-40) in aqueous trifluoroethanol (TFE) solution regarding its aggregation propensity and structural changes in comparison to its non-pyroglutamate-modified variant Aβ(1-40). Secondary structure analysis by circular dichroism spectroscopy suggests that pEAβ(3-40) shows an increased tendency to form β-sheet-rich structures in 20% TFE containing solutions where Aβ(1-40) forms α-helices. Aggregation kinetics of pEAβ(3-40) in the presence of 20% TFE monitored by thioflavin-T (ThT) assay showed a typical sigmoidal aggregation in contrast to A...
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PLOS ONE, 2015
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Scientific Reports, 2015
Strong evidence exists for a central role of amyloid β-protein (Aβ) oligomers in the pathogenesis... more Strong evidence exists for a central role of amyloid β-protein (Aβ) oligomers in the pathogenesis of Alzheimer's disease. We have developed a fast, reliable and robust in vitro assay, termed QIAD, to quantify the effect of any compound on the Aβ aggregate size distribution. Applying QIAD, we studied the effect of homotaurine, scyllo-inositol, EGCG, the benzofuran derivative KMS88009, ZAβ3W, the D-enantiomeric peptide D3 and its tandem version D3D3 on Aβ aggregation. The predictive power of the assay for in vivo efficacy is demonstrated by comparing the oligomer elimination efficiency of D3 and D3D3 with their treatment effects in animal models of Alzheimer´s disease.
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European Journal of Medical Research, 2014
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PLOS ONE, 2015
Targeting toxic amyloid beta (Aβ) oligomers is currently a very attractive drug development strat... more Targeting toxic amyloid beta (Aβ) oligomers is currently a very attractive drug development strategy for treatment of Alzheimer´s disease. Using mirror-image phage display against Aβ1-42, we have previously identified the fully D-enantiomeric peptide D3, which is able to eliminate Aβ oligomers and has proven therapeutic potential in transgenic Alzheimer´s disease animal models. However, there is little information on the pharmacokinetic behaviour of D-enantiomeric peptides in general. Therefore, we conducted experiments with the tritium labelled D-peptide D3 (3H-D3) in mice with different administration routes to study its distribution in liver, kidney, brain, plasma and gastrointestinal tract, as well as its bioavailability by i.p. and p.o. administration. In addition, we investigated the metabolic stability in liver microsomes, mouse plasma, brain, liver and kidney homogenates, and estimated the plasma protein binding. Based on its high stability and long biological half-life, our pharmacokinetic results support the therapeutic potential of D-peptides in general, with D3 being a new promising drug candidate for Alzheimer´s disease treatment.
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GBM Fall meeting Hamburg 2007, 2007
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PloS one, 2016
Amyloid deposits formed from islet amyloid polypeptide (IAPP) are a hallmark of type 2 diabetes m... more Amyloid deposits formed from islet amyloid polypeptide (IAPP) are a hallmark of type 2 diabetes mellitus and are known to be cytotoxic to pancreatic β-cells. The molecular structure of the fibrillar form of IAPP is subject of intense research, and to date, different models exist. We present results of solid-state NMR experiments on fibrils of recombinantly expressed and uniformly 13C, 15N-labeled human IAPP in the non-amidated, free acid form. Complete sequential resonance assignments and resulting constraints on secondary structure are shown. A single set of chemical shifts is found for most residues, which is indicative of a high degree of homogeneity. The core region comprises three to four β-sheets. We find that the central 23-FGAILS-28 segment, which is of critical importance for amyloid formation, is part of the core region and forms a β-strand in our sample preparation. The eight N-terminal amino acid residues of IAPP, forming a ring-like structure due to a disulfide bridge b...
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Scientific reports, Jan 19, 2016
In type 2 diabetes, the formation of islet amyloid consisting of islet amyloid polypeptide (IAPP)... more In type 2 diabetes, the formation of islet amyloid consisting of islet amyloid polypeptide (IAPP) is associated with reduction in β-cell mass and contributes to the failure of islet cell transplantation. Rational design of inhibitors of IAPP amyloid formation has therapeutic potential, but is hampered by the lack of structural information on inhibitor complexes of the conformationally flexible, aggregation-prone IAPP. Here we characterize a β-hairpin conformation of IAPP in complex with the engineered binding protein β-wrapin HI18. The β-strands correspond to two amyloidogenic motifs, 12-LANFLVH-18 and 22-NFGAILS-28, which are connected by a turn established around Ser-20. Besides backbone hydrogen bonding, the IAPP:HI18 interaction surface is dominated by non-polar contacts involving hydrophobic side chains of the IAPP β-strands. Apart from monomers, HI18 binds oligomers and fibrils and inhibits IAPP aggregation and toxicity at low substoichiometric concentrations. The IAPP β-hairp...
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Biophysical journal, Jan 25, 2017
Pyroglutamate-modified amyloid-β (pEAβ) has been described as a relevant Aβ species in Alzheimer&... more Pyroglutamate-modified amyloid-β (pEAβ) has been described as a relevant Aβ species in Alzheimer's-disease-affected brains, with pEAβ (3-42) as a dominant isoform. Aβ (1-40) and Aβ (1-42) have been well characterized under various solution conditions, including aqueous solutions containing trifluoroethanol (TFE). To characterize structural properties of pEAβ (3-42) possibly underlying its drastically increased aggregation propensity compared to Aβ (1-42), we started our studies in various TFE-water mixtures and found striking differences between the two Aβ species. Soluble pEAβ (3-42) has an increased tendency to form β-sheet-rich structures compared to Aβ (1-42), as indicated by circular dichroism spectroscopy data. Kinetic assays monitored by thioflavin-T show drastically accelerated aggregation leading to large fibrils visualized by electron microscopy of pEAβ (3-42) in contrast to Aβ (1-42). NMR spectroscopy was performed for backbone and side-chain chemical-shift assignment...
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European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences, Jan 30, 2017
The aggregation of the amyloid β protein (Aβ) plays an important role in the pathology of Alzheim... more The aggregation of the amyloid β protein (Aβ) plays an important role in the pathology of Alzheimer's disease. Previously, we have developed the all-d-enantiomeric peptide D3, which is able to eliminate neurotoxic Aβ oligomers in vitro and improve cognition in a transgenic Alzheimer's disease mouse model in vivo even after oral administration. d-Peptides are expected to be more resistant against enzymatic proteolysis compared to their l-enantiomeric equivalents, and indeed, a pharmacokinetic study with tritiated D3 revealed the oral bioavailability to be about 58%. To further investigate the underlying properties, we examined the stability of D3 in comparison to its corresponding all-l-enantiomeric mirror image l-D3 in media simulating the gastrointestinal tract, blood and liver. Potential metabolization was followed by reversed-phase high-performance liquid chromatography. In simulated gastric fluid, D3 remained almost completely stable (89%) within 24h, while 70% of l-D3 w...
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ACS chemical neuroscience, Jan 5, 2017
Amyloid-beta (Aβ) oligomers are thought to be causative for the development and progression of Al... more Amyloid-beta (Aβ) oligomers are thought to be causative for the development and progression of Alzheimer's disease (AD). Starting from the Aβ oligomer eliminating D-enantiomeric peptide D3, we developed and applied a two-step procedure based on peptide microarrays to identify D3 derivatives with increased binding affinity and specificity for monomeric Aβ(1-42) to further enhance the Aβ oligomer elimination efficacy. Out of more than 1,000 D3 derivatives, we selected seven novel D-peptides, named ANK1 to ANK7, and characterized them in more detail in vitro. All ANK peptides bound to monomeric Aβ(1-42), eliminated Aβ(1-42) oligomers, inhibited Aβ(1-42) fibril formation, and reduced Aβ(1-42)-induced cytotoxicity more efficiently than D3. Additionally, ANK6 completely inhibited the prion-like propagation of pre-formed Aβ(1-42) seeds and showed a non-significant tendency for improving memory performance of tg-APPSwDI mice after i.p. application for 4 weeks. This supports the hypothes...
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The Journal of biological chemistry, Jan 16, 2016
IQ motif-containing GTPase activating protein 1 (IQGAP1) plays a central role in the physical ass... more IQ motif-containing GTPase activating protein 1 (IQGAP1) plays a central role in the physical assembly of relevant signaling networks that are responsible for various cellular processes, including cell adhesion, polarity, and transmigration. The RHO family proteins CDC42 and RAC1 have been shown to mainly interact with the GAP-related domain (GRD) of IQGAP1. However, the role of its RASGAP C-terminal (RGCT) and C-terminal domains in the interactions with RHO proteins has remained obscure. Here, we demonstrate that IQGAP1 interactions with RHO proteins underlie a multiple-step binding mechanism: (i) a high affinity, GTP-dependent binding of RGCT to the switch regions of CDC42 or RAC1 and (ii) a very low affinity binding of GRD and a C terminus adjacent to the switch regions. These data were confirmed by phosphomimetic mutation of serine 1443 to glutamate within RGCT, which led to a significant reduction of IQGAP1 affinity for CDC42 and RAC1, clearly disclosing the critical role of RG...
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Biochemistry, 2016
The interaction of the amyloid-β protein (Aβ) with neuronal cell membranes plays a crucial role i... more The interaction of the amyloid-β protein (Aβ) with neuronal cell membranes plays a crucial role in Alzheimer's disease. Aβ undergoes structural changes upon binding to ganglioside GM1 containing membranes leading to altered molecular characteristics of the protein. The physiological role of the Aβ interaction with the ganglioside GM1 is still unclear. In order to further elucidate the molecular requirements of Aβ membrane binding, we tested different nanodiscs varying in their lipid composition, regarding the charge of the headgroups as well as ganglioside GM1 concentration. Nanodiscs are excellent model membrane systems for studying protein membrane interactions, and we show here their suitability to investigate the membrane interaction of Aβ. In particular, we set out to investigate whether the binding activity of GM1 to Aβ is specific for the assembly state of Aβ and compared the binding affinities of monomeric with oligomeric Aβ. Using fluorescence titration experiments, we demonstrate high-affinity binding of Aβ(1-40) to GM1 containing nanodiscs, with dissociation constants, KD, in the range from 25 to 41 nM, in a GM1 concentration-dependent manner. Biolayer interferometry experiments confirmed the high-affinity binding of monomeric Aβ(1-40) (KD of 24 nM to 49 nM) as well as of Aβ(1-42) (KD of 30 nM) to GM1 containing nanodiscs, and no binding to phospholipid containing nanodiscs. Interestingly, and in contrast to monomeric Aβ, neither oligomeric Aβ(1-40) nor oligomeric Aβ(1-42) binds to GM1 nanodiscs. To the best of our knowledge, this is the first report of a loss of function for monomeric Aβ upon aggregation.
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PLOS ONE, 2016
[This corrects the article DOI: 10.1371/journal.pone.0147470.].
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J Mol Biol, 2000
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Biochemistry Usa, Feb 1, 2003
The structurally characterized molybdoenzyme carbon monoxide dehydrogenase (CODH) catalyzes the o... more The structurally characterized molybdoenzyme carbon monoxide dehydrogenase (CODH) catalyzes the oxidation of CO to CO2 in the aerobic bacterium Oligotropha carboxidovorans. The active site of the enzyme was studied by Mo- and Cu-K-edge X-ray absorption spectroscopy. This revealed a bimetallic [Cu(I)SMo(VI)(double bond O)2] cluster in oxidized CODH which was converted into a [Cu(I)SMo(IV)(double bond O)OH2] cluster upon reduction. The Cu...Mo distance is 3.70 A in the oxidized form and is increased to 4.23 A upon reduction. The bacteria contain CODH species with the complete and functional bimetallic cluster along with enzyme species deficient in Cu and/or bridging S. The latter are precursors in the posttranslational biosynthesis of the metal cluster. Cu-deficient CODH is the most prominent precursor and contains a [HSMo(double bond O)OH2] cluster. Se-K-edge X-ray absorption spectroscopy demonstrates that Se is coordinated by two C atoms at 1.94-1.95 A distance. This is interpreted as a replacement of the S in methionine residues. In contrast to a previous report [Dobbek, H., Gremer, L., Meyer, O., and Huber, R. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 8884-8889] Se was not identified in the active site of CODH.
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ACS chemical neuroscience, Jan 9, 2016
Alzheimer's disease (AD) is a neurodegenerative disorder and the most common type of dementia... more Alzheimer's disease (AD) is a neurodegenerative disorder and the most common type of dementia. Until now, there is no curative therapy available. Previously, we selected the amyloid-beta (Aβ) targeting peptide D3 consisting of 12 d-enantiomeric amino acid residues by mirror image phage display as a potential drug candidate for the treatment of AD. In the current approach, we investigated the optimization potential of linear D3 with free C-terminus (D3COOH) by chemical modifications. First, the impact of the net charge was investigated and second, cyclization was introduced which is a well-known tool for the optimization of peptides for enhanced target affinity. Following this strategy, three D3 derivatives in addition to D3COOH were designed: C-terminally amidated linear D3 (D3CONH2), cyclic D3 (cD3), and cyclic D3 with an additional arginine residue (cD3r) to maintain the net charge of linear D3CONH2. These four compounds were compared to each other according to their binding a...
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Science signaling, Jan 24, 2016
Cerebral amyloid angiopathy (CAA) is a vascular dysfunction disorder characterized by deposits of... more Cerebral amyloid angiopathy (CAA) is a vascular dysfunction disorder characterized by deposits of amyloid-β (Aβ) in the walls of cerebral vessels. CAA and Aβ deposition in the brain parenchyma contribute to dementia and Alzheimer's disease (AD). We investigated the contribution of platelets, which accumulate at vascular Aβ deposits, to CAA. We found that synthetic monomeric Aβ40 bound through its RHDS (Arg-His-Asp-Ser) sequence to integrin αIIbβ3, which is the receptor for the extracellular matrix protein fibrinogen, and stimulated the secretion of adenosine diphosphate (ADP) and the chaperone protein clusterin from platelets. Clusterin promoted the formation of fibrillar Aβ aggregates, and ADP acted through its receptors P2Y1 and P2Y12 on platelets to enhance integrin αIIbβ3 activation, further increasing the secretion of clusterin and Aβ40 binding to platelets. Platelets from patients with Glanzmann's thrombasthenia, a bleeding disorder in which platelets have little or dy...
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PLOS ONE, 2016
The aggregation of amyloid-β (Aβ) is postulated to be the crucial event in Alzheimer&... more The aggregation of amyloid-β (Aβ) is postulated to be the crucial event in Alzheimer's disease (AD). In particular, small neurotoxic Aβ oligomers are considered to be responsible for the development and progression of AD. Therefore, elimination of thesis oligomers represents a potential causal therapy of AD. Starting from the well-characterized d-enantiomeric peptide D3, we identified D3 derivatives that bind monomeric Aβ. The underlying hypothesis is that ligands bind monomeric Aβ and stabilize these species within the various equilibria with Aβ assemblies, leading ultimately to the elimination of Aβ oligomers. One of the hereby identified d-peptides, DB3, and a head-to-tail tandem of DB3, DB3DB3, were studied in detail. Both peptides were found to: (i) inhibit the formation of Thioflavin T-positive fibrils; (ii) bind to Aβ monomers with micromolar affinities; (iii) eliminate Aβ oligomers; (iv) reduce Aβ-induced cytotoxicity; and (v) disassemble preformed Aβ aggregates. The beneficial effects of DB3 were improved by DB3DB3, which showed highly enhanced efficacy. Our approach yielded Aβ monomer-stabilizing ligands that can be investigated as a suitable therapeutic strategy against AD.
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PLOS ONE, 2016
Alzheimer´s disease is the most prominent type of dementia and currently no causative treatment i... more Alzheimer´s disease is the most prominent type of dementia and currently no causative treatment is available. According to recent studies, oligomeric species of the amyloid beta (Aβ) peptide appear to be the most toxic Aβ assemblies. Aβ monomers, however, may be not toxic per se and may even have a neuroprotective role. Here we describe a competitive mirror image phage display procedure that allowed us to identify preferentially Aβ1-42 monomer binding and thereby stabilizing peptides, which destabilize and thereby eliminate toxic oligomer species. One of the peptides, called Mosd1 (monomer specific d-peptide 1), was characterized in more detail. Mosd1 abolished oligomers from a mixture of Aβ1-42 species, reduced Aβ1-42 toxicity in cell culture, and restored the physiological phenotype in neuronal cells stably transfected with the gene coding for human amyloid precursor protein.
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PloS one, 2015
A hallmark of Alzheimer's disease (AD) is the accumulation of extracellular amyloid-β (Aβ) pl... more A hallmark of Alzheimer's disease (AD) is the accumulation of extracellular amyloid-β (Aβ) plaques in the brains of patients. N-terminally truncated pyroglutamate-modified Aβ (pEAβ) has been described as a major compound of Aβ species in senile plaques. pEAβ is more resistant to degradation, shows higher toxicity and has increased aggregation propensity and β-sheet stabilization compared to non-modified Aβ. Here we characterized recombinant pEAβ(3-40) in aqueous trifluoroethanol (TFE) solution regarding its aggregation propensity and structural changes in comparison to its non-pyroglutamate-modified variant Aβ(1-40). Secondary structure analysis by circular dichroism spectroscopy suggests that pEAβ(3-40) shows an increased tendency to form β-sheet-rich structures in 20% TFE containing solutions where Aβ(1-40) forms α-helices. Aggregation kinetics of pEAβ(3-40) in the presence of 20% TFE monitored by thioflavin-T (ThT) assay showed a typical sigmoidal aggregation in contrast to A...
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PLOS ONE, 2015
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Scientific Reports, 2015
Strong evidence exists for a central role of amyloid β-protein (Aβ) oligomers in the pathogenesis... more Strong evidence exists for a central role of amyloid β-protein (Aβ) oligomers in the pathogenesis of Alzheimer's disease. We have developed a fast, reliable and robust in vitro assay, termed QIAD, to quantify the effect of any compound on the Aβ aggregate size distribution. Applying QIAD, we studied the effect of homotaurine, scyllo-inositol, EGCG, the benzofuran derivative KMS88009, ZAβ3W, the D-enantiomeric peptide D3 and its tandem version D3D3 on Aβ aggregation. The predictive power of the assay for in vivo efficacy is demonstrated by comparing the oligomer elimination efficiency of D3 and D3D3 with their treatment effects in animal models of Alzheimer´s disease.
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European Journal of Medical Research, 2014
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PLOS ONE, 2015
Targeting toxic amyloid beta (Aβ) oligomers is currently a very attractive drug development strat... more Targeting toxic amyloid beta (Aβ) oligomers is currently a very attractive drug development strategy for treatment of Alzheimer´s disease. Using mirror-image phage display against Aβ1-42, we have previously identified the fully D-enantiomeric peptide D3, which is able to eliminate Aβ oligomers and has proven therapeutic potential in transgenic Alzheimer´s disease animal models. However, there is little information on the pharmacokinetic behaviour of D-enantiomeric peptides in general. Therefore, we conducted experiments with the tritium labelled D-peptide D3 (3H-D3) in mice with different administration routes to study its distribution in liver, kidney, brain, plasma and gastrointestinal tract, as well as its bioavailability by i.p. and p.o. administration. In addition, we investigated the metabolic stability in liver microsomes, mouse plasma, brain, liver and kidney homogenates, and estimated the plasma protein binding. Based on its high stability and long biological half-life, our pharmacokinetic results support the therapeutic potential of D-peptides in general, with D3 being a new promising drug candidate for Alzheimer´s disease treatment.
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GBM Fall meeting Hamburg 2007, 2007
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