1.
Restraint Stress in Rats Alters Gene Transcription and Protein Translation in the Hippocampus.
Source
Department of Psychiatry, Alzheimer's Disease Research Centre, University of Szeged, Kálvária sgt. 57, 6701, Szeged, Hungary, santha.petra@gmail.com.
Abstract
Stress is a relatively new and emerging risk factor for Alzheimer's disease (AD). Severe stress can alter brain characteristics such as neuronal plasticity, due to changes in the metabolism of cytoskeletal proteins. In this study, male Wistar rats were exposed to restraint stress (RS) for 5 h daily for different time periods. At the end of the exposure periods, the amounts of β-actin, cofilin, amyloid precursor protein (APP) and mitogen-activated protein kinase 1 (MAPK-1) RNAs and proteins were investigated. The mRNA expressions of β-actin, cofilin and MAPK-1 followed U-shaped time course. Acute (3 days) and chronic (21 days) RS caused a fourfold and tenfold increases, respectively, in hippocampal β-actin mRNA expression. In the case of cofilin mRNA expression, elevations were detected in the hippocampus on days 3, 7 and 21. The APP mRNA level was increased on day 21. On protein level, chronic stress elevated the levels of β-actin, cofilin and APP in the hippocampus. These results suggest that stress causes the induction of some genes andproteins that are also elevated in AD selectively in the hippocampal region of the rat brain.
- PMID:
- 22219132
- [PubMed - as supplied by publisher]
The AAA-ATPase VPS4 Regulates Extracellular Secretion and Lysosomal Targeting of α-Synuclein.
Source
Division of Neurology, Department of Neuroscience & Sensory Organs, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
Abstract
MANY NEURODEGENERATIVE DISEASES SHARE A COMMON PATHOLOGICAL FEATURE: the deposition ofamyloid-like fibrils composed of misfolded proteins. Emerging evidence suggests that these proteins may spread from cell-to-cell and encourage the propagation of neurodegeneration in a prion-like manner. Here, we demonstrated that α-synuclein (αSYN), a principal culprit for Lewy pathology in Parkinson's disease (PD), was present in endosomal compartments and detectably secreted into the extracellular milieu. Unlike prion protein, extracellular αSYN was mainly recovered in the supernatant fraction rather than in exosome-containing pellets from the neuronal culture medium and cerebrospinal fluid. Surprisingly, impaired biogenesis of multivesicular body (MVB), an organelle from which exosomes are derived, by dominant-negative mutant vacuolar protein sorting 4 (VPS4) not only interfered with lysosomal targeting of αSYN but facilitated αSYN secretion. The hypersecretion of αSYN in VPS4-defective cells was efficiently restored by the functional disruption of recycling endosome regulator Rab11a. Furthermore, both brainstem and cortical Lewy bodies in PD were found to be immunoreactive for VPS4. Thus, VPS4, a master regulator of MVB sorting, may serve as a determinant of lysosomal targeting or extracellular secretion of αSYN and thereby contribute to the intercellular propagation of Lewy pathology in PD.
- PMID:
- 22216284
- [PubMed - in process]
A Carrier for Non-Covalent Delivery of Functional Beta-Galactosidase and Antibodies against Amyloid Plaques and IgM to the Brain.
Source
Department of Experimental Pathology, Mayo Clinic, Rochester, Minnesota, United States of America.
Abstract
BACKGROUND:
Therapeutic intervention of numerous brain-associated disorders currently remains unrealized due to serious limitations imposed by the blood-brain-barrier (BBB). The BBB generally allows transport of small molecules, typically <600 daltons with high octanol/water partition coefficients, but denies passage to most larger molecules. However, some receptors present on the BBB allow passage of cognate proteins to the brain. Utilizing such receptor-ligand systems, several investigators have developed methods for delivering proteins to the brain, a critical requirement of which involves covalent linking of the target protein to a carrier entity. Such covalent modifications involve extensive preparative and post-preparative chemistry that poses daunting limitations in the context of delivery to any organ. Here, we report creation of a 36-amino acid peptide transporter, which can transport a protein to the brain after routine intravenous injection of the transporter-protein mixture. No covalent linkage of the protein with the transporter is necessary.
APPROACH:
A peptide transporter comprising sixteen lysine residues and 20 amino acids corresponding to the LDLR-binding domain of apolipoprotein E (ApoE) was synthesized. Transport of beta-galactosidase, IgG, IgM, and antibodies against amyloid plques to the brain upon iv injection of the protein-transporter mixture was evaluated through staining for enzyme activity or micro single photon emission tomography (micro-SPECT) or immunostaining. Effect of the transporter on the integrity of the BBB was also investigated.
PRINCIPAL FINDINGS:
The transporter enabled delivery to the mouse brain of functional beta-galactosidase, human IgG and IgM, and two antibodies that labeled brain-associated amyloid beta plaques in a mouse model of Alzheimer's disease.
SIGNIFICANCE:
The results suggest the transporter is able to transport most or all proteins to the brain without the need for chemically linking the transporter to a protein. Thus, the approach offers an avenue for rapid clinical evaluation of numerous candidate drugs against neurological diseases including cancer. (299 words).
- PMID:
- 22216132
- [PubMed - in process]
Transglutaminase 2: Biology, Relevance to Neurodegenerative Diseases and Therapeutic Implications.
Abstract
Neurodegenerative disorders are characterized by progressive neuronal loss and the aggregation of disease-specific pathogenic proteins in hallmark neuropathologic lesions. Many of these proteins, including amyloid Αβ, tau, α-synuclein and huntingtin, are cross-linked by the enzymatic activity of transglutaminase 2 (TG2). Additionally, the expression and activity of TG2 is increased in affected brain regions in these disorders. These observations along with experimental evidence in cellular and mouse models suggest that TG2 can contribute to the abnormal aggregation of disease causingproteins and consequently to neuronal damage. This accumulating evidence has provided the impetus to develop inhibitors of TG2 as possible neuroprotective agents. However, TG2 has other enzymatic activities in addition to its cross-linking function and can modulate multiple cellular processes including apoptosis, autophagy, energy production, synaptic function, signal transduction and transcription regulation. These diverse properties must be taken into consideration in designing TG2 inhibitors. In this review, we discuss the biochemistry of TG2, its various physiologic functions and our current understanding about its role in degenerative diseases of the brain. We also describe the different approaches to designing TG2 inhibitors that could be developed as potential disease-modifying therapies.
Copyright © 2011. Published by Elsevier Inc.
Mapping out the multi-stage fibrillation of glucagon.
Source
Interdisciplinary Nanoscience Center, Center for Insoluble Protein Structures, Department of Molecular Biology and Genetics, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C, DENMARK Department of Biomedicine, Aarhus University, Wilhelm Meyers Alle, DK-8000 Aarhus C, DENMARK Novo Nordisk A/S, Hagedornsvej 1, DK-2820 Gentofte, DENMARK Danish Power Systems Ltd., Technical University of Denmark, Kemitorvet, DK-2800 Lyngby, DENMARK. SciAssist ApS, Wildersgade 26A, DK-1408 Copenhagen K, DENMARK.
Abstract
The 29-residue peptide hormone glucagon forms many different morphological types of amyloid-like fibrils, depending on solvent conditions. Here, we combine time-series far-UV circular dichroism with singular value decomposition (SVD) analysis to reveal six different conformational states populated during fibrillation at 25°C and pH 2.5. The existence of these states is supported by complementary fluorescence and electron microscopy data. This highlights a multitude of structural transitions of glucagon from unordered structure to β-sheets, β-turns and further tertiary level changes. We attribute the observed unusual far-UV CD spectra to tertiary level structural changes during the formation and maturation of fibrils. The fibrillation model for the whole process involves formation of three oligomeric species and two different morphologies of fibrils in the same solution. The visualization of annular pore-like species in the early stages of glucagon fibrillation and the prevalence of such species in the amyloidogenesis of several proteins indicates that they may be a common feature of the fibrillation process. This study gives significant insights on the stepwise conversion of soluble glucagon to its fibrillar state and identifies the importance of fibril twisting for its thermodynamic stabilization. STRUCTUREDDIGITALABSTRACT: Glucagon and Glucagon bind by circular dichroism (View interaction) Glucagon and Glucagon bind by transmission electron microscopy (View interaction) Glucagon and Glucagon bind by fluorescence technology (View interaction).
Journal compilation © 2011 Federation of European Biochemical Societies.
Management of moderate to severe Alzheimer's disease: Focus on memantine.
Source
Department of Bioscience Technology, Chung Yuan Christian University, Chung Li, Taiwan.
Abstract
Alzheimer's disease (AD) is the most common form of dementia, and one of the principal causes leading to death around the world. It is a progressive neurodegenerative disorder that still remains without definite cure. Memantine, a licensed AD drug, is an open-channel and partial trapping blocker that functions as a potent NMDA receptor antagonist, even at low concentrations. Aside from being uncompetitive, it also allows near-normal physiological NMDA receptor activity throughout the brain even with high glutamate concentrations, making it more reliable and tolerable than other AD-targeted drugs. It has also been found to be effective, safe, and well-tolerated in animal models as well as patients with moderate-to-severe AD. Aside from NMDA receptor antagonism, numerous studies have reported that memantine can also affect dopamine receptors, block excessive calcium influx and production of reactive oxygen species (ROS) induced by Aβ oligomers, and inhibit the internal ribosome entry site (IRES), thus preventing the expression of theamyloid precursor and tau proteins which are considered as early indicators of Alzheimer's.
Copyright © 2011. Published by Elsevier B.V.
Amphiphilic Adsorption of Human Islet Amyloid Polypeptide Aggregates to Lipid/Aqueous Interfaces.
Abstract
Many amyloid proteins misfold into β-sheet aggregates upon interacting with biomembranes at the onset of diseases, such as Parkinson's disease and type II diabetes. The molecular mechanisms triggering aggregation depend on the orientation of β-sheets at the cell membranes. However, understanding how β-sheets adsorb onto lipid/aqueous interfaces is challenging. Here, we combine chiral sum frequency generation (SFG) spectroscopy and ab initio quantum chemistry calculations based on a divide-and-conquer strategy to characterize the orientation of human islet amyloidpolypeptides (hIAPPs) at lipid/aqueous interfaces. We show that the aggregates bind with β-strands oriented at 48° relative to the interface. This orientation reflects the amphiphilic properties of hIAPP β-sheet aggregates and suggests the potential disruptive effect on membrane integrity.
Copyright © 2011. Published by Elsevier Ltd.
Acute phase proteins in healthy and sick cats.
Source
School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia.
Abstract
Serum acute phase protein concentrations are used as diagnostic, therapeutic and prognostic markers in human and, less frequently, in animal medicine. The aim of this study was to determine how the health status and signalment of the cat are associated with concentrations of acute phase proteins. Generally, medians of the positive acute phase proteinsappeared to be higher in sick cats compared to healthy cats. In multivariable regression models, log-transformed serumamyloid A concentration was higher in older cats, in sick and in female cats, while log-transformed α1-acid glycoprotein and haptoglobin concentrations were higher in older cats and were associated with interactions of health status (sick/healthy) and gender (male/female). The data from healthy cats in this study contribute to the limited knowledge of normal reference ranges for this species. This study highlights the potential of acute phase proteins as diagnostic markers in sick cats, but also emphasises that the signalment of the cat needs to be taken into consideration.
Copyright © 2011 Elsevier Ltd. All rights reserved.
Sensitivity of Amyloid Formation by Human Islet Amyloid Polypeptide to Mutations at Residue 20.
Source
Department of Chemistry, Stony Brook University, Stony Brook, NY 11794-3400, USA.
Abstract
Islet amyloid polypeptide (IAPP, amylin) is responsible for amyloid formation in type 2 diabetes and in islet cell transplants. The only known natural mutation found in mature human IAPP is a Ser20-to-Gly missense mutation, found with small frequency in Chinese and Japanese populations. The mutation appears to be associated with increased risk of early-onset type 2 diabetes. Early measurements in the presence of organic co-solvents showed that S20G-IAPP formed amyloid more quickly than the wild type. We confirm that the mutant accelerates amyloid formation under a range of conditions including in the absence of co-solvents. Ser20 adopts a normal backbone geometry, and the side chain makes no steric clashes in models of IAPP amyloid fibers, suggesting that the increased rate of amyloidformation by the mutant does not result from the relief of steric incompatibility in the fiber state. Transmission electronic microscopy, circular dichroism, and seeding studies were used to probe the structure of the resulting fibers. The S20G-IAPP peptide is toxic to cultured rat INS-1 (transformed rat insulinoma-1) β-cells. The sensitivity of amyloid formation to the identity of residue 20 was exploited to design a variant that is much slower to aggregate and that inhibits amyloidformation by wild-type IAPP. An S20K mutant forms amyloid with an 18-fold longer lag phase. Thioflavin T binding assays, together with experiments using a p-cyanophenylalanine (p-cyanoPhe) variant of human IAPP, show that the designed S20K mutant inhibits amyloid formation by human IAPP. The experiments illustrate how p-cyanoPhe can be exploited to monitor amyloid formation even in the presence of other amyloidogenic proteins.
Copyright © 2011. Published by Elsevier Ltd.
The Nogo receptor 2 is a novel substrate of Fbs1.
Source
Neurobiochemistry - Biocenter, Innsbruck Medical University, Fritz-Preglstraße 3, 6020 Innsbruck, Austria.
Abstract
Members of the Nogo66 receptor family (NgR) are closely associated with nerve growth inhibition and plasticity in the CNS. All three members, NgR1, NgR2 and NgR3, are GPI anchored and highly glycosylated proteins. The binding and signaling properties of NgR1 are well described, but largely unknown for NgR2. At present the only known ligands are myelin associated glycoprotein (MAG) and amyloid beta precursor protein (APP). Despite the requirement of co-receptors for signaling no other binding partner has been uncovered. To learn more about the interactome of NgR2 we performed pull down experiments and were able to identify F-box protein that recognizes sugar chain 1 (Fbs1) as binding partner. We confirmed this finding with co-immunoprecipitations and in vitro binding assays and showed that the binding is mediated by the substrate recognition domain of Fbs1. As a substrate recognition protein of the SCF complex, Fbs1 binding leads to polyubiquitination and finally degradation of its substrates. This is the first time a member of the Nogo receptor family has been connected with an intracellular degradation pathway, which has not only implications for its production, but also for amyloid deposition in Alzheimer's disease.
Copyright © 2011. Published by Elsevier Inc.
Fibrillar Amyloid-β1-42 Modifies Actin Organization Affecting the Cofilin Phosphorylation State: A Role for Rac1/cdc42 Effector Proteins and the Slingshot Phosphatase.
Source
Laboratory of Cellular and Molecular Neurosciences, University of Chile and International Center for Biomedicine (ICC), Santiago, Chile.
Abstract
The neuronal cytoskeleton regulates numerous processes that occur in normal homeostasis. Under pathological conditions such as those of Alzheimer's disease (AD), major alterations in cytoskeleton organization have been observed and changes in both microtubules and actin filaments have been reported. Many neurodegenerative consequences of AD are linked to the production and accumulation of amyloid peptides (Aβ) and their oligomers, produced from the internal cleavage of the amyloid-β protein precursor. We previously reported that fibrillar Aβ1-42 (fAβ) treatment of hippocampal neurons induced an increase in Rac1 and Cdc42 activities linking fAβ effects with changes in actin dynamics. Here we show fAβ-induces increased activity of PAK1 and cyclin-dependent kinase 5, and that p21-activated kinase (PAK1) activation targets the LIMK1-cofilin signaling pathway. Increased cofilin dephosphorylation under conditions of enhanced LIM-Kinase 1 (LIMK1) activity suggests that fAβ co-stimulates bifurcating pathways impacting cofilin phosphorylation. Overexpression of slingshot (SSH) prevents the augment of F-actin induced by fAβ after 24 h, suggesting that fAβ-induced changes in actin assembly involve both LIMK1 and SSH. These results suggest that fAb may alter the PAK1/LIMK1/cofilin axis and therefore actin organization in AD.
Transgenic neuronal overexpression reveals that stringently regulated p23 expression is critical for coordinated movement in mice.
Abstract
ABSTRACT:
BACKGROUND:
p23 belongs to the highly conserved p24 family of type I transmembrane proteins, which participate in bidirectional protein transport between the endoplasmic reticulum and Golgi apparatus. Mammalian p23 has been shown to interact with gamma-secretase complex, and modulate secretory trafficking as well as intramembranous processing of amyloid precursor protein in cultured cells. Negative modulation of beta-amyloid production by p23 in cultured cell lines suggested that elevation of p23 expression in neurons might mitigate cerebral amyloid burden.
RESULTS:
We generated several lines of transgenic mice expressing human p23 in neurons under the control of Thy-1.2 promoter. We found that even a 50% increase in p23 levels in the central nervous system of mice causes post-natal growth retardation, severe neurological problems characterized by tremors and seizure, ataxia, and uncoordinated movements, and premature death. The severity of the phenotype closely correlated with the level of p23 overexpression in multiple transgenic lines. While the number and general morphology of neurons in Hup23 mice appeared to be normal throughout the brain, abnormal non-Golgi p23 localization was observed in a subset of neurons with high transgene expression in brainstem. Moreover, detailed immunofluorescence analysis revealed marked proliferation of astrocytes, activation of microglia, and thinning of myelinated bundles in brainstem of Hup23 mice.
CONCLUSIONS:
These results demonstrate that proper level of p23 expression is critical for neuronal function, and perturbing p23 function by overexpression initiates a cascade of cellular reactions in brainstem that leads to severe motor deficits and other neurological problems, which culminate in premature death. The neurological phenotype observed in Hup23 mice highlights significant adverse effects associated with manipulating neuronal expression of p23, a previously described negative modulator of gamma-secretase activity and beta-amyloid production. Moreover, our report has broader relevance to molecular mechanisms in several neurodegenerative diseases as it highlights the inherent vulnerability of the early secretory pathway mechanisms that ensure proteostasis in neurons.
Therapeutic targets of brain insulin resistance in sporadic Alzheimer's disease.
Source
Departments of Neurology, Neurosurgery, and Neuropathology, Rhode Island Hospital and the Alpert Medical School of Brown University, Providence, RI.
Abstract
Growing evidence supports roles for brain insulin and insulin-like growth factor (IGF) resistance and metabolic dysfunction in the pathogenesis of Alzheimer's disease (AD). Whether the underlying problem stems from a primary disorder of central nervous system (CNS) neurons and glia, or secondary effects of systemic diseases such as obesity, Type 2 diabetes, or metabolic syndrome, the end-results include impaired glucose utilization, mitochondrial dysfunction, increased oxidative stress, neuroinflammation, and the propagation of cascades that result in the accumulation of neurotoxic misfolded, aggregated, and ubiquitinated fibrillar proteins. This article reviews the roles of impaired insulin and IGF signaling to AD-associated neuronal loss, synaptic disconnection, tau hyperphosphorylation, amyloid-beta accumulation, and impaired energy metabolism, and discusses therapeutic strategies and lifestyle approaches that could be used to prevent, delay the onset, or reduce the severity of AD. Finally, it is critical to recognize that AD is heterogeneous and has a clinical course that fully develops over a period of several decades. Therefore, early and multi-modal preventive and treatment approaches should be regarded as essential.
- PMID:
- 22201977
- [PubMed - in process]
Estrogen receptors in lipid raft signalling complexes for neuroprotection.
Source
Laboratory of Cellular Neurobiology, Department of Physiology, School of Medicine; Institute of Biomedical Technologies, La Laguna University; and Canarian Institute of Cancer Research, Tenerife, Spain.
Abstract
Estrogens exert a plethora of actions conducted to brain preservation and functioning. Some of these actions are initiated in lipid rafts, which are particular microstructures of the plasma membrane. Preservation of lipid raft structure in neurons is essential for signal transduction against different injuries, such as Alzheimer's disease (AD). These membrane structures appear to be disrupted as this neuropathology evolves, and that may largely contribute to dysfunction of raft resident proteins involved in intracellular signalling. This review includes a survey of some protein interactions that are involved in the structural maintenance and signal transduction mechanisms for neuronal survival against AD. Particularly relevant are the rapid mechanisms developed by estrogen to prevent neuronal death, through membrane estrogen receptors (mER) interactions with a voltage-dependent anion channel (VDAC) and other protein markers within neuronal lipid rafts. These interactions may have important consequences in estrogen mechanisms to achieve neuroprotection against amyloid beta (Abeta-induced toxicity).
- PMID:
- 22201966
- [PubMed - in process]
Metals in alzheimer's disease: a systemic perspective.
Source
Department of Neuroscience, AFaR, Fatebenefratelli Hospital, Rome, Italy, Department of Neurology, Campus Biomedico, University, Rome, Italy.
Abstract
Many results from in vitro and animal studies have highlighted the important role played by specific metals, such as copper, iron and zinc, in the diverse toxic pathways on which Alzheimer's disease (AD) develops. Metals seem to mediate the aggregation and neurotoxicity of amyloid-beta (ABeta), the main constituent of the amyloid plaques, commonly seen in AD (1). The link between metals and AD has been mostly investigated with a focus on their local accumulation in defined areas of the brain critical for AD. In the present review, I have instead approached the issue from the different perspective of a systemic, rather than local, alteration of copper and iron status. This view is supported by the results of a series of in vivo studies demonstrating that abnormalities of metals homeostasis correlate with the main deficits and specific markers of AD, such as ABeta and Tau proteins in the cerebrospinal fluid. These findings clearly suggest that local metals accumulation in brain areas critical for AD should be viewed within a wider framework of metals systemic alteration.
- PMID:
- 22201755
- [PubMed - in process]
HIV-Associated Neurological Disorders: A Guide to Pharmacotherapy.
Source
Department of Neurology, School of Medicine, Johns Hopkins University, Baltimore, MD, USA.
Abstract
In the era of highly active antiretroviral therapy (HAART), HIV-1-associated neurocognitive disorder (HAND) continues to be a common and significant morbidity among individuals infected with HIV. The term HAND encompasses a spectrum of progressively severe CNS involvement, ranging from asymptomatic neurocognitive impairment and minor neurocognitive disorder through to the most severe form of HIV-associated dementia (HAD). While the incidence of HAD has declined significantly with HAART, the milder forms of HAND persist. In addition, HAND now develops in individuals with less advanced immunosuppression. The reasons for the persistence of milder forms of HAND in individuals treated with HAART are not entirely known. There are several hypotheses to explain this phenomenon that include the legacy effect, a failure of antiretroviral agents to reverse neurological damage, poor access of antiretroviral agents to the CNS, chronic systemic immune activation associated with microbial translocation products, sustained CNS inflammation, the improved survival of HIV-seropositive individuals and the possible contribution from aging, amyloid deposition and other co-morbidities. In contrast, the incidence of HIV-associated CNS opportunistic processes including progressive multifocal leukoencephalopathy, tuberculosis, CNS toxoplasmosis, cytomegalovirus encephalitis, cryptococcosis and primary CNS lymphoma has declined dramatically with the introduction of HAART. This review briefly summarizes our current understanding of HAND and the pathological mechanisms involved, namely direct injury from HIV-1 and viralproteins, indirect neurotoxicity from proinflammatory cytokines and chronic, sustained immune activation in the CNS. To date, only HAART has been shown to benefit HAND despite numerous controlled trials of adjunctive 'anti-inflammatory' agents. Although HAART has a profound impact on the incidence and severity of HAND, there exists a 'therapeutic gap' as even HAART that is effective at inducing durable virological suppression may only partially reverse HAND. In addition, there may be potential CNS adverse effects of antiretroviral agents. There is an ongoing multicentre clinical trial to investigate the role of the CNS Penetration-Effectiveness index, an indicator of drug permeability and availability in the CNS, to help guide the choice of antiretroviral agents in the treatment of HAND. With recent recommendations for earlier treatment intervention with HAART for HIV-1 infection, it remains to be seen the effects of this on HAND. There is an urgent need to better define the therapeutic guidelines for the prevention and treatment of HAND.
Formation of supramolecular structures of a native-like protein in the presence of amphiphilic peptides: Variations in aggregate morphology.
Source
A.N. Bakh Institute of Biochemistry, Russian Academy of Sciences, Leninsky Prospect, 33, 119071 Moscow, Russia.
Abstract
A striking potential of the amphiphilic dipeptides, Arg-Phe or Asp-Phe, to induce aggregation of a model protein, alcohol dehydrogenase in its native-like state, has been demonstrated under physiologically relevant conditions, using dynamic light scattering, fluorescence spectroscopy, circular dichroism, transmission electron- and atomic force microscopy. The peptide action resulted in accumulation of a variety of morphologically distinct supramolecular structures profoundly differing from those generated by the heat-induced aggregation at the early stages of the process, when amyloid fibril assemblies were not detectable. The biogenic amphiphilic agents are suggested to act as regulators of structural transformations of native-like proteins.
Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
Effect of N-homocysteinylation on physicochemical and cytotoxic properties ofamyloid β-peptide.
Source
Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
Abstract
Abstract Hyperhomocysteinemia has recently been identified as an important risk factor for Alzheimer's disease (AD). One of the potential mechanisms underlying harmful effects of homocysteine (Hcy) is site-specific acylation of proteinsat lysine residues by homocysteine thiolactone (HCTL). The accumulation of amyloid β-peptide (Aβ) in the brain is a neuropathological hallmark of AD. In the present study we were interested to investigate the effects of N-homocysteinylation on the aggregation propensity and neurotoxicity of Aβ(1-42). By coupling several techniques, we demonstrated that the homocysteinylation of lysine residues increase the neurotoxicity of the Aβ peptide by stabilizing soluble oligomeric intermediates. STRUCTURED SUMMARY OF PROTEIN INTERACTIONS: A Beta 1-42 and A Beta 1-42bind by fluorescence technology (View interaction) A Beta 1-42 and A Beta 1-42bind by electron microscopy (View interaction).
Copyright © 2011. Published by Elsevier B.V.
The Effect of Amyloidogenic Peptides on Bacterial Aging Correlates with Their Intrinsic Aggregation Propensity.
Source
Institut de Biotecnologia i Biomedicina and Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.
Abstract
The formation of aggregates by misfolded proteins is thought to be inherently toxic, affecting cell fitness. This observation has led to the suggestion that selection against protein aggregation might be a major constraint on protein evolution. The precise fitness cost associated with protein aggregation has been traditionally difficult to evaluate. Moreover, it is not known if the detrimental effect of aggregates on cell physiology is generic or depends on the specific structural features of the protein deposit. In bacteria, the accumulation of intracellular protein aggregates reduces cell reproductive ability, promoting cellular aging. Here, we exploit the cell division defects promoted by the intracellular aggregation of Alzheimer's-disease-related amyloid β peptide in bacteria to demonstrate that the fitness cost associated with protein misfolding and aggregation is connected to the protein sequence, which controls both the in vivo aggregation rates and the conformational properties of the aggregates. We also show that the deleterious impact of protein aggregation on bacterial division can be buffered by molecular chaperones, likely broadening the sequential space on which natural selection can act. Overall, the results in the present work have potential implications for the evolution ofproteins and provide a robust system to experimentally model and quantify the impact of protein aggregation on cell fitness.
Copyright © 2011 Elsevier Ltd. All rights reserved.
Water's potential role: Insights from studies of the p53 core domain.
Source
Center of Bioinformatics, Northwest A&F University, Yangling, 712100 Shaanxi, China; College of Life Sciences, Northwest A&F University, Yangling, 712100 Shaanxi, China.
Abstract
Soluble proteins with amyloidogenic propensity such as the tumor suppressor protein p53 have high proportion of incompletely desolvated backbone H bonds (HB). Such bonds are vulnerable to water attack, thus potentially leading to the misfolding of these proteins. However, it is still not clear how the surrounding solvent influences the protein native states. To address this, systematic surveys by molecular dynamics simulations and entropy analysis were performed on the p53 core domain in this work. We examined seven wild/mutant X-ray structures and observed two types of water-network hydration in three "hot hydration centers" (DNA- or small molecule- binding surfaces of the p53 core domain). The "tight" water, resulting from the local collective hydrogen-bond interactions, is probably fundamental to the protein structural stability. The second type of water is highly "dynamical" and exchanges very fast within the bulk solution, which is unambiguously assisted by the local protein motions. An entropy mapping of the solvent around the protein and a temperature perturbation analysis further present the main features of the p53 hydration network. The particular environment created by different water molecules around the p53 core domain also partly explains the structural vulnerabilities of this protein.
No comments:
Post a Comment