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  • 1
    Publication Date: 2022-05-25
    Description: © The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Neuroscience 31 (2011): 9858-9868, doi:10.1523/JNEUROSCI.0560-11.2011.
    Description: Aggregated filamentous forms of hyperphosphorylated tau (a microtubule-associated protein) represent pathological hallmarks of Alzheimer's disease (AD) and other tauopathies. While axonal transport dysfunction is thought to represent a primary pathogenic factor in AD and other neurodegenerative diseases, the direct molecular link between pathogenic forms of tau and deficits in axonal transport remain unclear. Recently, we demonstrated that filamentous, but not soluble, forms of wild-type tau inhibit anterograde, kinesin-based fast axonal transport (FAT) by activating axonal protein phosphatase 1 (PP1) and glycogen synthase kinase 3 (GSK3), independent of microtubule binding. Here, we demonstrate that amino acids 2–18 of tau, comprising a phosphatase-activating domain (PAD), are necessary and sufficient for activation of this pathway in axoplasms isolated from squid giant axons. Various pathogenic forms of tau displaying increased exposure of PAD inhibited anterograde FAT in squid axoplasm. Importantly, immunohistochemical studies using a novel PAD-specific monoclonal antibody in human postmortem tissue indicated that increased PAD exposure represents an early pathogenic event in AD that closely associates in time with AT8 immunoreactivity, an early marker of pathological tau. We propose a model of pathogenesis in which disease-associated changes in tau conformation lead to increased exposure of PAD, activation of PP1-GSK3, and inhibition of FAT. Results from these studies reveal a novel role for tau in modulating axonal phosphotransferases and provide a molecular basis for a toxic gain-of-function associated with pathogenic forms of tau.
    Description: This work was supported by NIH Grants T32 AG020506-07 (N.M.K.); AG09466 (L.I.B.); and NS23868, NS23320, and NS41170 (S.T.B.); as well as 2007/2008 MBL Summer Research Fellowships and an ALS/CVS Therapy Alliance grant (G.M.).
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-05-26
    Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS ONE 8 (2013): e65235, doi:10.1371/journal.pone.0065235.
    Description: Dying-back degeneration of motor neuron axons represents an established feature of familial amyotrophic lateral sclerosis (FALS) associated with superoxide dismutase 1 (SOD1) mutations, but axon-autonomous effects of pathogenic SOD1 remained undefined. Characteristics of motor neurons affected in FALS include abnormal kinase activation, aberrant neurofilament phosphorylation, and fast axonal transport (FAT) deficits, but functional relationships among these pathogenic events were unclear. Experiments in isolated squid axoplasm reveal that FALS-related SOD1 mutant polypeptides inhibit FAT through a mechanism involving a p38 mitogen activated protein kinase pathway. Mutant SOD1 activated neuronal p38 in mouse spinal cord, neuroblastoma cells and squid axoplasm. Active p38 MAP kinase phosphorylated kinesin-1, and this phosphorylation event inhibited kinesin-1. Finally, vesicle motility assays revealed previously unrecognized, isoform-specific effects of p38 on FAT. Axon-autonomous activation of the p38 pathway represents a novel gain of toxic function for FALS-linked SOD1 proteins consistent with the dying-back pattern of neurodegeneration characteristic of ALS.
    Description: Support was provided by 2007/2008 Marine Biological Laboratory summer fellowships and NIH (NS066942A) grants to GM; Howard Hughes Medical Institute-USE Grant #52006287 to Hunter College of CUNY (LM); Muscular Dystrophy Association (MDA) and NIH (R01NS44170) grants to LJH; MDA and NIH (NS23868, NS23320, NS41170) grants to STB; NIH grant MH066179 to GB; NIH grants R01AG031311 and R01NS055951 to DMW; NIH (U01NS05225, R01NS050557, 1RC1NS068391, 1RC2NS070342) grants to RHB; R01NS067206 to DAB; ALS Association grants to GM, AT, RHB, and STB; and ALS/CVS Therapy Alliance grants to RHB, GM, AT, LJH, and DAB. RHB and AT received support from the Angel Fund. RHB also received support from the DeBourgknecht Fund for ALS Research, P2ALS and Project ALS.
    Repository Name: Woods Hole Open Access Server
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  • 3
    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 7 (2017): 115, doi:10.1038/s41598-017-00091-1.
    Description: Mutations in Fused in Sarcoma/Translocated in Liposarcoma (FUS) cause familial forms of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease characterized by progressive axonal degeneration mainly affecting motor neurons. Evidence from transgenic mouse models suggests mutant forms of FUS exert an unknown gain-of-toxic function in motor neurons, but mechanisms underlying this effect remain unknown. Towards this end, we studied the effect of wild type FUS (FUS WT) and three ALS-linked variants (G230C, R521G and R495X) on fast axonal transport (FAT), a cellular process critical for appropriate maintenance of axonal connectivity. All ALS-FUS variants impaired anterograde and retrograde FAT in squid axoplasm, whereas FUS WT had no effect. Misfolding of mutant FUS is implicated in this process, as the molecular chaperone Hsp110 mitigated these toxic effects. Interestingly, mutant FUS-induced impairment of FAT in squid axoplasm and of axonal outgrowth in mammalian primary motor neurons involved aberrant activation of the p38 MAPK pathway, as also reported for ALS-linked forms of Cu, Zn superoxide dismutase (SOD1). Accordingly, increased levels of active p38 MAPK were detected in post-mortem human ALS-FUS brain tissues. These data provide evidence for a novel gain-of-toxic function for ALS-linked FUS involving p38 MAPK activation.
    Description: We are grateful for funding from NIH/NINDS (R01 NS078145, R01 NS090352, and R21 NS091860 to D.A.B., R01 NS066942A and R21 NS096642 to G.M., R01NS023868 and R01NS041170 to S.T.B.), the ALS Therapy Alliance/CVS Pharmacy (to D.A.B. and G.M.) and the ALS Association (to C.F. and J.M.).
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 12 (2017): e0188340, doi:10.1371/journal.pone.0188340.
    Description: Prion diseases include a number of progressive neuropathies involving conformational changes in cellular prion protein (PrPc) that may be fatal sporadic, familial or infectious. Pathological evidence indicated that neurons affected in prion diseases follow a dying-back pattern of degeneration. However, specific cellular processes affected by PrPc that explain such a pattern have not yet been identified. Results from cell biological and pharmacological experiments in isolated squid axoplasm and primary cultured neurons reveal inhibition of fast axonal transport (FAT) as a novel toxic effect elicited by PrPc. Pharmacological, biochemical and cell biological experiments further indicate this toxic effect involves casein kinase 2 (CK2) activation, providing a molecular basis for the toxic effect of PrPc on FAT. CK2 was found to phosphorylate and inhibit light chain subunits of the major motor protein conventional kinesin. Collectively, these findings suggest CK2 as a novel therapeutic target to prevent the gradual loss of neuronal connectivity that characterizes prion diseases.
    Description: This work was supported by Alzheimer Association New Investigator Research Grant to Promote Diversity NIRGD-11-206379 and Consejo Nacional de Investigaciones Científicas y Técnicas PIP 112 20150100954 CO (to GP), National Institutes of Health NS066942A and NS096642 (to GM), R01-NS023868 and R01-NS041170 (to STB).
    Repository Name: Woods Hole Open Access Server
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  • 5
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in ASN Neuro 8 (2016): 10.1177/1759091416679073, doi:10.1177/1759091416679073.
    Description: Sensory neuropathies are the most common neurological complication of HIV. Of these, distal sensory polyneuropathy (DSP) is directly caused by HIV infection and characterized by length-dependent axonal degeneration of dorsal root ganglion (DRG) neurons. Mechanisms for axonal degeneration in DSP remain unclear, but recent experiments revealed that the HIV glycoprotein gp120 is internalized and localized within axons of DRG neurons. Based on these findings, we investigated whether intra-axonal gp120 might impair fast axonal transport (FAT), a cellular process critical for appropriate maintenance of the axonal compartment. Significantly, we found that gp120 severely impaired both anterograde and retrograde FAT. Providing a mechanistic basis for these effects, pharmacological experiments revealed an involvement of various phosphotransferases in this toxic effect, including members of mitogen-activated protein kinase pathways (Tak-1, p38, and c-Jun N-terminal Kinase (JNK)), inhibitor of kappa-B-kinase 2 (IKK2), and PP1. Biochemical experiments and axonal outgrowth assays in cell lines and primary cultures extended these findings. Impairments in neurite outgrowth in DRG neurons by gp120 were rescued using a Tak-1 inhibitor, implicating a Tak-1 mitogen-activated protein kinase pathway in gp120 neurotoxicity. Taken together, these observations indicate that kinase-based impairments in FAT represent a novel mechanism underlying gp120 neurotoxicity consistent with the dying-back degeneration seen in DSP. Targeting gp120-based impairments in FAT with specific kinase inhibitors might provide a novel therapeutic strategy to prevent axonal degeneration in DSP.
    Description: The project described was supported by the National Center for Advancing Translational Sciences, National Institutes of Health, through Grant TL1TR000049 and by the NIH grant T32MH067631 to SHB; NIH grants NS066942A to GM; and grants from the National Institutes of Neurological Disorders and Stroke [NS023868 and NS041170] to STB; and a pilot grant from the Chicago DCFAR [P30AI083151], the UIC Center for Clinical and Translational Sciences, and the Chicago Biomedical Consortium to STB.
    Keywords: Axonal transport ; Distal sensory polyneuropathy ; Gp120 ; HIV ; Mitogen-activated protein kinase ; Kinesin
    Repository Name: Woods Hole Open Access Server
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  • 6
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Song, Y. Synaptic actions of amyotrophic-lateral-sclerosis-associated G85R-SOD1 in the squid giant synapse. Eneuro, (2020): ENEURO.0369-19.2020, doi: 10.1523/ENEURO.0369-19.2020.
    Description: Altered synaptic function is thought to play a role in many neurodegenerative diseases, but little is known about the underlying mechanisms for synaptic dysfunction. The squid giant synapse (SGS) is a classical model for studying synaptic electrophysiology and ultrastructure, as well as molecular mechanisms of neurotransmission. Here, we conduct a multidisciplinary study of synaptic actions of misfolded human G85R-SOD1 causing familial Amyotrophic Lateral Sclerosis (fALS). G85R-SOD1, but not WT-SOD1, inhibited synaptic transmission, altered presynaptic ultrastructure, and reduced both the size of the Readily Releasable Pool (RRP) of synaptic vesicles and mobility from the Reserved Pool (RP) to the RRP. Unexpectedly, intermittent high frequency stimulation (iHFS) blocked inhibitory effects of G85R-SOD1 on synaptic transmission, suggesting aberrant Ca2+ signaling may underlie G85R-SOD1 toxicity. Ratiometric Ca2+ imaging showed significantly increased presynaptic Ca2+ induced by G85R-SOD1 that preceded synaptic dysfunction. Chelating Ca2+ using EGTA prevented synaptic inhibition by G85R-SOD1, confirming the role of aberrant Ca2+ in mediating G85R-SOD1 toxicity. These results extended earlier findings in mammalian motor neurons and advanced our understanding by providing possible molecular mechanisms and therapeutic targets for synaptic dysfunctions in ALS as well as a unique model for further studies.
    Description: Grass Foundation, HHMI, MGH Jack Satter Foundation, Harvard University ALS and Alzheimer's Endowed Research Fund, Harvard Brain Science Initiative.
    Keywords: Amyotrophic-Lateral-Sclerosis-Associated ; calcium ; giant synapse ; neurodegeneration ; SOD1 ; synaptic vesicles
    Repository Name: Woods Hole Open Access Server
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  • 7
    Publication Date: 2018-11-14
    Description: Drug receptor site occupancy is a central pharmacology parameter that quantitatively relates the biochemistry of drug binding to the biology of drug action. Taxanes and epothilones bind to overlapping sites in microtubules (MTs) and stabilize them. They are used to treat cancer and are under investigation for neurodegeneration. In cells, they cause concentration-dependent inhibition of MT dynamics and perturbation of mitosis, but the degree of site occupancy required to trigger different effects has not been measured. We report a live cell assay for taxane-site occupancy, and relationships between site occupancy and biological effects across four drugs and two cell lines. By normalizing to site occupancy, we were able to quantitatively compare drug activities and cell sensitivities independent of differences in drug affinity and uptake/efflux kinetics. Across all drugs and cells tested, we found that inhibition of MT dynamics, postmitotic micronucleation, and mitotic arrest required successively higher site occupancy. We also found interesting differences between cells and drugs, for example, insensitivity of the spindle assembly checkpoint to site occupancy. By extending our assay to a mouse xenograft tumor model, we estimated the initial site occupancy required for paclitaxel to completely prevent tumor growth as 80%. The most important cellular action of taxanes for cancer treatment may be formation of micronuclei, which occurs over a broad range of site occupancies.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 8
    Publication Date: 2016-11-22
    Description: Magnetic fields from neuronal action potentials (APs) pass largely unperturbed through biological tissue, allowing magnetic measurements of AP dynamics to be performed extracellularly or even outside intact organisms. To date, however, magnetic techniques for sensing neuronal activity have either operated at the macroscale with coarse spatial and/or temporal resolution—e.g., magnetic resonance imaging methods and magnetoencephalography—or been restricted to biophysics studies of excised neurons probed with cryogenic or bulky detectors that do not provide single-neuron spatial resolution and are not scalable to functional networks or intact organisms. Here, we show that AP magnetic sensing can be realized with both single-neuron sensitivity and intact organism applicability using optically probed nitrogen-vacancy (NV) quantum defects in diamond, operated under ambient conditions and with the NV diamond sensor in close proximity (∼10 µm) to the biological sample. We demonstrate this method for excised single neurons from marine worm and squid, and then exterior to intact, optically opaque marine worms for extended periods and with no observed adverse effect on the animal. NV diamond magnetometry is noninvasive and label-free and does not cause photodamage. The method provides precise measurement of AP waveforms from individual neurons, as well as magnetic field correlates of the AP conduction velocity, and directly determines the AP propagation direction through the inherent sensitivity of NVs to the associated AP magnetic field vector.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
  • 10
    Publication Date: 2012-10-10
    Description: Environmental Science & Technology DOI: 10.1021/es3011282
    Print ISSN: 0013-936X
    Electronic ISSN: 1520-5851
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
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