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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: To investigate the cellular mechanisms regulating neurofilament-heavy subunit (NF-H) side-arm phosphorylation, we studied the ability of three putative neurofilament kinases, glycogen synthase kinase-3 (GSK-3)α, GSK-3β, and cyclin-dependent kinase-5 (cdk-5), to phosphorylate NF-H in transfected cells. We analysed NF-H phosphorylation by using a panel of phosphorylation-dependent antibodies and also by monitoring the electrophoretic mobility of the transfected NF-H on sodium dodecyl sulphate-polyacrylamide gel electrophoresis because this is known to be affected by side-arm phosphorylation. Our results demonstrate that whereas GSK-3α, GSK-3β, and cdk-5 will all phosphorylate NF-H, they generate different antibody reactivity profiles. GSK-3α and GSK-3β induce a partial retardation of a proportion of the transfected NF-H, but only cdk-5 alters the rate of electrophoretic migration to that of NF-H from brain. We conclude that cdk-5 and GSK-3 phosphorylate different residues or sets of residues within NF-H sidearms in cells. We further show that cdk-5 is active in both the CNS and the PNS but that this activity is not dependent on expression of its activator, p35. This suggests that there are other activators of cdk-5.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 66 (1996), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Ser55 within the head domain of neurofilament light chain (NF-L) is transiently phosphorylated by protein kinase A, and phosphorylation of this residue is thought to regulate assembly of neurofilaments. To understand how Ser55 phosphorylation influences NF-L assembly, wild-type and mutant NF-L genes in which Ser55 was mutated to alanine, so as to prevent phosphorylation, or to aspartate, so as to mimic permanent phosphorylation, were transfected into mammalian cells that contain or do not contain an endogenous intermediate filament network. Wild-type and mutant NF-Ls localised to the Triton X-100-insoluble fraction, which suggests that phosphorylation of Ser55 does not inhibit assembly of NF-L and NF-L/vimentin polymers at or below the tetrameric stage. Immunofluorescence microscopy of transfected cells demonstrated that the wild-type and mutant NF-Ls all colocalised with vimentin to produce similar filamentous arrays. However, in cells lacking an endogenous intermediate filament network, the aspartate mutant produced a pattern of staining different from that of the wild-type or alanine mutant. These results suggest that phosphorylation of NF-L Ser55 is not a mechanism that precludes assembly of neurofilaments from monomers into intermediate filament structures but that phosphorylation/dephosphorylation of this residue might confer more subtle characteristics on neurofilament assembly properties and architecture.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 70 (1998), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Cyclin-dependent kinase-5 (cdk-5) is a serine/threonine kinase that displays neurone-specific activity. Experimental manipulation of cdk-5 expression in neurones has shown that cdk-5 is essential for proper development of the nervous system and, in particular, for outgrowth of neurites. Such observations suggest that cdk-5 activity must be tightly controlled during development of the nervous system. To identify possible regulators of cdk-5, we used the yeast two-hybrid system to search for proteins that interact with cdk-5. In two independent yeast transformation events, cyclin D2 interacted with cdk-5. Immunoprecipitation experiments confirmed that cyclin D2 and cdk-5 interact in mammalian cells. Cyclin D2 did not activate cdk-5 as assayed using three different substrates, which was in contrast to a known cdk-5 activator, p35. However, cyclin D2 expression led to a decrease in cdk-5/p35 activity in transfected cells. As cyclin D2 and cdk-5 are known to share overlapping patterns of expression during development of the CNS, the results presented here suggest a role for cyclin D2 in modulating cdk-5 activity in postmitotic developing neurones.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The side-arm domain of neurofilament heavy-chain (NF-H) is heavily phosphorylated in axons. Much of this phosphate is located within a multiphosphorylation repeat (MPR) domain situated toward the carboxy terminus of the molecule. The MPR domain contains the repeat motif KSP of which there are two broad categories, KSPXX and KSPXK. In mouse NF-H, the KSPXK repeats are situated toward the latter part of the MPR domain. We have expressed in mammalian cells fragments of mouse NF-H side-arm containing all of the MPR domain, the latter part of the MPR domain containing the KSPXK repeats, and the complementary amino-terminal part of the MPR domain, which contains the KSPXX repeats. By cotransfecting these fragments with the neurofilament kinases cyclin-dependent kinase-5 (cdk-5)/p35 and glycogen synthase kinase-3α (GSK-3α), we show that cdk-5 induces cellular phosphorylation of the KSPXK-containing fragment of NF-H. Using the transfected fragments, we also map the epitopes for several commonly utilised NF-H monoclonal antibodies and describe the effects that phosphorylation by cdk-5 and GSK-3α have on their reactivities.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Ser55 within the head domain of neurofilament light chain (NF-L) is a target for phosphorylation by protein kinase A. To understand further the physiological role(s) of NF-L Ser55 phosphorylation, we generated transgenic mice with a mutant NF-L transgene in which Ser55 was mutated to Asp so as to mimic permanent phosphorylation. Two lines of NF-L(Asp) mice were created and these animals express the transgene in many neurones of the central and peripheral nervous systems. Both transgenic lines display identical, early onset, and robust pathological changes in the brain. These involve the formation of NF-L(Asp)-containing perikaryal neurofilament inclusion bodies and the development of swollen Purkinje cell axons. Development of these pathologies was rapid and fully established in mice as young as 4 weeks of age. The two transgenic lines show no elevation of NF-L, neurofilament middle chain (NF-M), or neurofilament heavy chain (NF-H), and transgenic NF-L(Asp) represents only a minor proportion of total NF-L protein. Because other published transgenic lines expressing higher levels of wild-type NF-L do not exhibit phenotypic changes that in any way resemble those in the NF-L(Asp) mice and because the two different NF-L(Asp) transgenic lines display identical neuropathological changes, it is likely that the pathological alterations observed in the NF-L(Asp) mice are the result of properties of the mutant NF-L. These results support the notion that phosphorylation of Ser55 is a mechanism for regulating neurofilament organisation in vivo.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Aberrant metabolism of the amyloid precursor protein (APP) is believed to be at least part of the pathogenic process in Alzheimer’s disease. The carboxy-terminus of APP has been shown to interact with the Mint/X11 family of phosphotyrosine binding (PTB) domain-bearing proteins. It is via their PTB domains that the Mints/X11s bind to APP. Here we report the cloning of full-length mouse Mint2 and demonstrate that in primary cortical neurons, Mint2 and APP share highly similar distributions. Mint2 also colocalizes with APP in transfected CHO cells. In Mint2/APP-cotransfected cells, Mint2 reorganizes the subcellular distribution of APP and also increases the steady-state levels of APP. Finally, we demonstrate that Mint2 is associated with the neuritic plaques found in Alzheimer’s disease but not with neurofibrillary tangles. These results are consistent with a role for Mint2 in APP metabolism and trafficking, and suggest a possible role for the Mints/X11s in the pathogenesis of Alzheimer’s disease.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature medicine 2 (1996), S. 751-752 
    ISSN: 1546-170X
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Sexual transmission is the most common route for dissemination of human immunodeficiency virus (HIV) worldwide, and a vaccine capable of preventing sexual transmission might prove an effective way of halting the spread of AIDS. To be effective such a vaccine must prevent HIV transmission by three ...
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1546-170X
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Simian immunodeficiency virus (SIV) can cross the intact vaginal epithelium to establish a systemic infection in macaques (mac). Using this SIVmac model, we found that subcutaneous progesterone implants, which could mimic hormonally based contraceptives, thinned the vaginal epithelium and enhanced ...
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 389 (1997), S. 328-329 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Proteins are intelligent beings. They have evolved to operate in the metabolic maelstrom of a turbulent cellular environment. Transcription factors must know when to switch genes on or off, and the cellular levels of specific ‘signalling’ molecules — lactose, retinoic acid, ...
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 384 (1996), S. 103-103 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR — The relentless decline of scientific culture, the venality of senior researchers, the torments of junior academic scientists battle-scarred by the blunderbuss of the National Institutes of Health and the National Science Foundation — these things always make news. But is it really ...
    Type of Medium: Electronic Resource
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