Presenilin-1 P264L knock-in mutation: differential effects on abeta production, amyloid deposition, and neuronal vulnerability.
The pathogenic mechanism linking presenilin-1 (PS-1) gene mutations to familial Alzheimer's disease (FAD) is uncertain, but has been proposed to include increased neuronal sensitivity to degeneration and enhanced amyloidogenic processing of the beta-amyloid precursor protein (APP). We investigated this issue by using gene targeting with the Cre-lox system to introduce an FAD-linked P264L mutation into the endogenous mouse PS-1 gene, an approach that maintains normal regulatory controls over expression. Primary cortical neurons derived from PS-1 homozygous mutant knock-in mice exhibit basal neurodegeneration similar to their PS-1 wild-type counterparts. Staurosporine and Abeta1-42 induce apoptosis, and neither the dose dependence nor maximal extent of cell death is altered by the PS-1 knock-in mutation. Similarly, glutamate-induced neuronal necrosis is unaffected by the PS-1P264L mutation. The lack of effect of the PS-1P264L mutation is confirmed by measures of basal- and toxin-induced caspase and calpain activation, biochemical indices of apoptotic and necrotic signaling, respectively. To analyze the influence of the PS-1P264L knock-in mutation on APP processing and the development of AD-type neuropathology, we created mouse lines carrying mutations in both PS-1 and APP. In contrast to the lack of effect on neuronal vulnerability, cortical neurons cultured from PS-1P264L homozygous mutant mice secrete Abeta42 at an increased rate, whereas secretion of Abeta40 is reduced. Moreover, the PS-1 knock-in mutation selectively increases Abeta42 levels in the mouse brain and accelerates the onset of amyloid deposition and its attendant reactive gliosis, even as a single mutant allele. We conclude that expression of an FAD-linked mutant PS-1 at normal levels does not generally increase cortical neuronal sensitivity to degeneration. Instead, enhanced amyloidogenic processing of APP likely is critical to the pathogenesis of PS-1-linked FAD.
Siman
R
R
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA. siman@pharm.med.upenn.edu
Reaume
A G
AG
Savage
M J
MJ
Trusko
S
S
Lin
Y G
YG
Scott
R W
RW
Flood
D G
DG
D000544:Alzheimer Disease / Q000209:etiology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D019943:Amino Acid Substitution; D000682:Amyloid / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000096:biosynthesis* / Q000378:metabolism / Q000494:pharmacology; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002154:Calpain / Q000378:metabolism; D020169:Caspases / Q000302:isolation & purification / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D018390:Gene Targeting; D018698:Glutamic Acid / Q000494:pharmacology; D006720:Homozygote; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D053764:Presenilin-1; D019311:Staurosporine / Q000494:pharmacology
D000682:Amyloid; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D008565:Membrane Proteins; D010446:Peptide Fragments; D053764:Presenilin-1; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42); D018698:Glutamic Acid; D002154:Calpain; D020169:Caspases; D019311:Staurosporine