title: Physiological levels of beta-amyloid peptide stimulate protein kinase C in PC12 cells.
abstract: Alzheimer's beta-amyloid peptide (A beta) is normally present at nanomolar concentrations in body fluids and in the medium of cultured cells. In vitro experiments have shown that A beta has neurotrophic effects and can promote neuronal adhesion and elongation of axon-like processes. In an attempt to understand the molecular mechanisms underlying such effects, we have recently reported that nanomolar doses of A beta can stimulate protein tyrosine phosphorylation and activate phosphatidylinositol-3-kinase in neuronal cells. Here we show evidence that A beta can also activate protein kinase C, a serine/threonine kinase, in PC12 cells. First, using a serine-containing S6 peptide as an exogenous substrate, we found that nanomolar levels of A beta peptides 1-40 or 1-42 significantly stimulated an S6 phosphorylating kinase activity, whereas the A beta40-1 reverse sequence peptide had no effect. Down-regulation of PKC by prolonged (18 h) treatment with 1 microM PMA prevented the A beta-induced S6 phosphorylation. Using a more specific PKC substrate, N-terminal acetylated peptide (4-14) from myelin basic protein, we then demonstrated that A beta indeed increased PKC activity and that this activity could be blocked by the PKC inhibitor, staurosporine. Finally, immunoblotting experiments showed that A beta induced translocation of PKCgamma from cytosol to membrane and also significantly reduced cytosolic PKCalpha levels. Taken together, these data suggest that physiological levels of A beta can regulate PKC activity.
authors.affiliation: Molecular Physiology and Genetics Section, Gerontology Research Center, NIA, Baltimore, MD 21224, USA. luoyq@helix.nih.gov
authors.forename: Y
authors.initials: Y
authors.lastname: Luo
authors.forename: D B
authors.initials: DB
authors.lastname: Hawver
authors.forename: K
authors.initials: K
authors.lastname: Iwasaki
authors.forename: T
authors.initials: T
authors.lastname: Sunderland
authors.forename: G S
authors.initials: GS
authors.lastname: Roth
authors.forename: B
authors.initials: B
authors.lastname: Wolozin
mesh_terms: D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D016716:PC12 Cells / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats
chemical_list: D016229:Amyloid beta-Peptides; D007527:Isoenzymes; C087857:protein kinase C gamma; D017346:Protein Serine-Threonine Kinases; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha