Physiological levels of beta-amyloid peptide stimulate protein kinase C in PC12 cells.
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.
Luo
Y
Y
Molecular Physiology and Genetics Section, Gerontology Research Center, NIA, Baltimore, MD 21224, USA. luoyq@helix.nih.gov
Hawver
D B
DB
Iwasaki
K
K
Sunderland
T
T
Roth
G S
GS
Wolozin
B
B
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
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