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      Amyloid beta-mediated cell death of cultured hippocampal neurons reveals extensive Tau fragmentation without increased full-length tau phosphorylation.

      The Journal of Biological Chemistry

      Amyloid beta-Peptides, genetics, metabolism, pharmacology, Animals, Caspase 3, Caspase 7, Cell Death, drug effects, Cells, Cultured, Cyclin-Dependent Kinase 5, Enzyme Activation, Glycogen Synthase Kinase 3, Hippocampus, pathology, Humans, Mitogen-Activated Protein Kinase 1, Mitogen-Activated Protein Kinase 3, Neurons, Phosphorylation, Proto-Oncogene Proteins c-akt, Rats, Rats, Sprague-Dawley, tau Proteins

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          Abstract

          A variety of genetic and biochemical evidence suggests that amyloid β (Aβ) oligomers promote downstream errors in Tau action, in turn inducing neuronal dysfunction and cell death in Alzheimer and related dementias. To better understand molecular mechanisms involved in Aβ-mediated neuronal cell death, we have treated primary rat hippocampal cultures with Aβ oligomers and examined the resulting cellular changes occurring before and during the induction of cell death with a focus on altered Tau biochemistry. The most rapid neuronal responses upon Aβ administration are activation of caspase 3/7 and calpain proteases. Aβ also appears to reduce Akt and Erk1/2 kinase activities while increasing GSK3β and Cdk5 activities. Shortly thereafter, substantial Tau degradation begins, generating relatively stable Tau fragments. Only a very small fraction of full-length Tau remains intact after 4 h of Aβ treatment. In conflict with expectations based on suggested increases of GSK3β and Cdk5 activities, Aβ does not cause any major increases in phosphorylation of full-length Tau as assayed by immunoblotting one-dimensional gels with 11 independent site- and phospho-specific anti-Tau antibodies as well as by immunoblotting two-dimensional gels probed with a pan-Tau antibody. There are, however, subtle and transient increases in Tau phosphorylation at 3-4 specific sites before its degradation. Taken together, these data are consistent with the notion that Aβ-mediated neuronal cell death involves the loss of full-length Tau and/or the generation of toxic fragments but does not involve or require hyperphosphorylation of full-length Tau.

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          Author and article information

          Journal
          21482827
          3121465
          10.1074/jbc.M111.234674

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