title: Alzheimer's-specific effects of soluble beta-amyloid on protein kinase C-alpha and -gamma degradation in human fibroblasts.
abstract: Alzheimer's disease (AD) is a multifactorial disease in which beta-amyloid peptide (betaAP) plays a critical role. We report here that the soluble fraction 1-40 of betaAP differentially degrades protein kinase C-alpha and -gamma (PKCalpha and PKCgamma) isoenzymes in normal (age-matched controls, AC) and AD fibroblasts most likely through proteolytic cascades. Treatment with nanomolar concentrations of betaAP(1-40) induced a 75% decrease in PKCalpha, but not PKCgamma, immunoreactivity in AC fibroblasts. In the AD fibroblasts, a 70% reduction of the PKCgamma, but not PKCalpha, immunoreactivity was observed after betaAP treatment. Preincubation of AC or AD fibroblasts with 50 microM lactacystine, a selective proteasome inhibitor, prevented beta-AP(1-40)-mediated degradation of PKCalpha in the AC cells, and PKCgamma in the AD fibroblasts. The effects of betaAP(1-40) on PKCalpha in AC fibroblasts were prevented by inhibition of protein synthesis and reversed by PKC activation. A 3-hr treatment with 100 nM phorbol 12-myristate 13-acetate restored the PKCalpha signal in treated AC cells but it did not reverse the effects of betaAP(1-40) on PKCgamma in the AD fibroblasts. Pretreatment with the protein synthesis inhibitor, cycloheximide (CHX, 100 microM), inhibited the effects of betaAP(1-40) on PKCalpha and blocked the rescue effect of phorbol 12-myristate 13-acetate in AC fibroblasts but did not modify PKCgamma immunoreactivity in AD cells. These results suggest that betaAP(1-40) differentially affects PKC regulation in AC and AD cells via proteolytic degradation and that PKC activation exerts a protective role via de novo protein synthesis in normal but not AD cells.
authors.affiliation: Laboratory of Adaptive Systems, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: A
authors.initials: A
authors.lastname: Favit
authors.forename: M
authors.initials: M
authors.lastname: Grimaldi
authors.forename: T J
authors.initials: TJ
authors.lastname: Nelson
authors.forename: D L
authors.initials: DL
authors.lastname: Alkon
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D000544:Alzheimer Disease / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D005347:Fibroblasts / Q000201:enzymology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D016229:Amyloid beta-Peptides; D007527:Isoenzymes; D010446:Peptide Fragments; D011500:Protein Synthesis Inhibitors; C078592:amyloid beta-protein (1-40); C067713:lactacystin; D003513:Cycloheximide; C087857:protein kinase C gamma; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D013755:Tetradecanoylphorbol Acetate; D000111:Acetylcysteine