Beta-amyloid inhibits NOS activity by subtracting NADPH availability.
The amyloid peptides Abeta1-42 and Abeta25-35 strongly inhibited the activity of constitutive neuronal and endothelial nitric oxide synthases (i.e., NOS-I and NOS-III, respectively) in cell-free assays. The molecular mechanism of NOS inhibition by Ab fragments was studied in detail with Abeta25-35. The inhibitory ability was mostly NADPH-dependent and specific for the soluble form of Abeta25-35. Optical, fluorescence, and NMR spectroscopy showed that the soluble, but not aggregated, Abeta25-35 interacted with NADPH, thus suggesting that a direct recruitment of NADPH may result in diminished availability of the redox cofactor for NOS functioning. To assess the physiological relevance of our findings, rat neuronal-like PC12 and glioma C6 cell lines were used as cellular models. After Abeta25-35 internalization into cells was verified, the activity of constitutive NOS was measured using the DAF-2DA detection system and found to be severely impaired upon Abeta25-35 uptake. Consistent with previous results on the molecular cross-talk between NOS isoforms, repression of constitutive NOS by Abeta25-35 resulted in enhanced expression of inducible NOS (NOS-II) mRNA in C6 cells. Our results represent the first evidence that amyloid fragments impair constitutive NOS activity in cell-free and cellular systems, providing a possible molecular mechanism for the onset and/or maintenance of Alzheimer's disease.
Venturini
Giorgio
G
Department of Biology, University Roma Tre, Rome, Italy.
Colasanti
Marco
M
Persichini
Tiziana
T
Fioravanti
Emanuela
E
Ascenzi
Paolo
P
Palomba
Letizia
L
Cantoni
Orazio
O
Musci
Giovanni
G
D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D009249:NADP / Q000737:chemistry / Q000494:pharmacology*; D009457:Neuroglia / Q000201:enzymology; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D016716:PC12 Cells; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured
D016229:Amyloid beta-Peptides; D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D012333:RNA, Messenger; C075222:amyloid beta-protein (1-42); C074636:amyloid beta-protein (25-35); D009249:NADP; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496322:Nos1 protein, rat; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat