Activation of LA-N-2 cell phospholipase D by amyloid beta protein (25-35).
Amyloid beta protein is the major protein component of neuritic plaques found in the brain of Alzheimer's disease. The activation of phospholipase D by amyloid beta protein (25-35), quisqualate and phorbol 12, 13-dibutyrate was investigated in LA-N-2 cells by measuring phosphatidylethanol formation. The activation of phospholipase D by quisqualate and APP (25-35) was calcium-independent. The AbetaP (25-35) and quisqualate activation of phospholipase D appeared to be mediated through a pertussis toxin-sensitive GTP-binding protein. Phospholipase D activation by AbetaP (25-35), quisqualate and phorbol dibutyrate was not blunted by the protein kinase C inhibitors, staurosporine, H-7 and RO-31-8220. However, it was abolished by overnight exposure to phorbol dibutyrate. This activation of phospholipase D was prevented by the tyrosine kinase inhibitor, genistein but not by tyrophostin A. Several excitatory amino acid antagonists were tested for their ability to prevent the phospholipase D activation by quisqualate and AbetaP (25-35). Only NBQX was effective with an IC50 of 75 microM for AbetaP (25-35) and quisqualate. Activation of phospholipase D by AbetaP or quisqualate was absent in LA-N-2 cells previously desensitized by quisqualate or AbetaP (25-35), but the activation by phorbol dibutyrate was unaltered. The responsiveness to AbetaP and quisqualate in previously desensitized cells reappeared subsequent to a period of resensitization. The observations with the antagonist NBQX, and the desensitization and resensitization experiments, are consistent with a receptor occupancy mediated activation of phospholipase D by quisqualate and by AbetaP (25-35).
Singh
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IN
Department of Biochemistry and Molecular Biology, University of Manitoba, Faculty of Medicine, Winnipeg, Canada.
Sorrentino
G
G
Kanfer
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JN
D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D016318:Quisqualic Acid / Q000494:pharmacology; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists
D016229:Amyloid beta-Peptides; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D010446:Peptide Fragments; D018094:Receptors, Metabotropic Glutamate; C113041:amyloid beta-protein (35-25); D015240:Phorbol 12,13-Dibutyrate; D016318:Quisqualic Acid; D011494:Protein Kinases; D010739:Phospholipase D; D019204:GTP-Binding Proteins