Fragment 31-35 of beta-amyloid peptide induces neurodegeneration in rat cerebellar granule cells via bax gene expression and caspase-3 activation. A crucial role for the redox state of methionine-35 residue.
The amyloid beta-peptide (AbetaP) is the major protein component of brain senile plaques in Alzheimer's disease. The redox state of methionine-35 residue plays a critical role in peptide neurotoxic actions. We used the fragment 31-35 of AbetaP [AbetaP(31-35)], containing a single methionine-35 residue (Met-35), to investigate the relationship between the oxidative state of Met-35 and neurotoxic and pro-apoptotic actions induced by the peptide; in rat cerebellar granule cells (CGC), we compared the effects of AbetaP(31-35), in which the Met-35 is present in the reduced state, with those of a modified peptide with oxidized Met-35 [AbetaP(31-35)Met-35(OX)](,) as well as an AbetaP-derivative with Met-35 substituted by norleucine [AbetaP(31-35)Nle-35]. AbetaP(31-35) induced a time-dependent decrease in cell viability. AbetaP(31-35)Met-35(OX) was significantly less potent, but still induced a significant decrease in cell viability compared to control. No toxic effects were observed after treatment with AbetaP(31-35)Nle-35. AbetaP(31-35) induced a 2-fold increase in bax mRNA levels after 4h, whereas AbetaP(31-35)Met-35(OX) raised bax mRNA levels by 41% and AbetaP(31-35)Nle-35 had no effect. Finally, AbetaP(31-35) caused a 43% increase in caspase-3 activity after 24h; AbetaP(31-35)Met-35(OX) caused only a 18% increase, and AbetaP(31-35)Nle-35 had no effect. These findings suggest that AbetaP(31-35)-induced neurodegeneration in CGC is mediated by a selective early increase in bax mRNA levels followed by delayed caspase-3 activation; the redox state of the single Met-35 residue is crucial in the occurrence and extent of the above phenomena.
Misiti
Francesco
F
Institute of Biochemistry and Clinical Biochemistry, Catholic University School of Medicine, Largo F. Vito 1, 00168 Rome, Italy.
Clementi
M Elisabetta
ME
Tringali
Giuseppe
G
Vairano
Mauro
M
Orsini
Federica
F
Pezzotti
Michela
M
Navarra
Pierluigi
P
Giardina
Bruno
B
Pozzoli
Giacomo
G
D016229:Amyloid beta-Peptides / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D002531:Cerebellum / Q000187:drug effects* / Q000473:pathology; D003594:Cytoplasmic Granules / Q000187:drug effects*; D004789:Enzyme Activation; D005786:Gene Expression Regulation / Q000187:drug effects*; D008715:Methionine / Q000378:metabolism*; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D051028:bcl-2-Associated X Protein / Q000235:genetics*
D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C113042:amyloid beta-protein (31-35); D051028:bcl-2-Associated X Protein; D008715:Methionine; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases