Presenilin 1 Interacts with Acetylcholinesterase and Alters Its Enzymatic Activity and Glycosylation

Abstract

Presenilin 1 (PS1) plays a critical role in the ␥-secretase processing of the amyloid precursor protein to generate the ␤-amyloid peptide, which accumulates in plaques in the pathogenesis of Alzheimer's disease (AD). Mutations in PS1 cause early onset AD, and proteins that interact with PS1 are of major functional importance. We report here the coimmunoprecipitation of PS1 and acetylcholinesterase (AChE), an enzyme associated with amyloid plaques. Binding occurs through PS1 N-terminal fragment independent of the peripheral binding site of AChE. Subcellular colocalization of PS1 and AChE in cultured cells and coexpression patterns of PS1 and AChE in brain sections from controls and subjects with sporadic or familial AD indicated that PS1 and AChE are located in the same intracellular compartments, including the perinuclear compartments. A PS1-A246E pathogenic mutation expressed in transgenic mice leads to decreased AChE activity and alteration of AChE glycosylation and the peripheral binding site, which may reflect a shift in protein conformation and disturbed AChE maturation. In both the transgenic mice and humans, mutant PS1 impairs coimmunoprecipitation with AChE. The results indicate that PS1 can interact with AChE and influence its expression, supporting the notion of cholinergic-amyloid interrelationships.Alzheimer's disease (AD) is characterized by the presence of large numbers of amyloid plaques and neurofibrillary tangles in the brain (56). The major constituent of the amyloid plaques is the ␤-amyloid protein (A␤), a polypeptide generated by processing of a much larger amyloid precursor protein (APP) through the successive action of two proteolytic enzymes, ␤-secretase and ␥-secretase (71). ␥-Secretase is a membrane protease complex comprising presenilin 1 (PS1) as a catalytic subunit (76). The importance of PS was first highlighted by genetic studies of AD. Families bearing mutations in the PS1 gene, or in the highly homologous presenilin 2 (PS2) gene, invariably develop an aggressive form of early-onset AD with an accelerated rate of A␤ deposition (75).The accumulation of A␤ peptide in the brain is thought to be an important step in the pathogenesis of AD, leading to a number of neurodegenerative changes (19). In particular, there is a decrease in cholinergic activity in the basal forebrain of AD patients, which affects activity of the acetylcholinesynthesizing enzyme, choline acetyltransferase, as well as the acetylcholine-hydrolyzing enzyme, acetylcholinesterase (AChE) (13, 53). The altered expression of AChE in the AD-affected brain (AD brain) is of particular interest. Despite an overall decrease in the AD brain, the activity of AChE is increased around the amyloid plaques (42,78). This may be a direct consequence of amyloid deposition, since A␤ peptides influence AChE levels in cell cultures (25,69) and in the brains of transgenic mice that produce human A␤ (70). Conversely, AChE may play a role in A␤ fibrillogenesis (27,60). Finally, several investigations have argued for a strict interrelation b...

Altered Levels of Acetylcholinesterase in Alzheimer Plasma

“…Accordingly, using non-denaturing polyacrylamide gels stained for AChE activity, molecular weights of AChE subunits are in the range of 70–75 kDa. However, analysis by SDS-PAGE and Western blotting by us and others, under fully reducing conditions and with several different anti-AChE antibodies, detected bands ranging from 75 to 50 kDa, for the AChE protein from different sources and animal species, including humans [30], [37], [44], [56]–[60]. The specificity of the 78 kDa AChE bands and of the lower molecular weight AChE bands was confirmed by immunoprecipitation, Fas2 affinity matrix binding and immunodetection of blots with different anti-human AChE antibodies (including the N-terminal N-19 and the ab31276 antibody, which recognizes the C-terminal residues 601–614 of human AChE-T) and is in agreement with our previous study in human CSF [30].…”

Acetylcholinesterase Protein Level Is Preserved in the Alzheimer's Brain

“…We have recently demonstrated an interaction between AChE and presenilin-1 (PS1), the catalytic component of the γ-secretase complex (Silveyra et al, 2008;2012a). γ-Secretase is a proteolytic enzymatic complex that participates in the processing of the amyloid precursor protein (APP), generating the β-amyloid peptide or Aβ (Kaether et al, 2006), the major constituent of the amyloid plaques (Masters et al, 1985;Kang et al, 1987).…”

The role of protein glycosylation in Alzheimer disease

“…In fact, it has been suggested that both Ab and tau induce the altered glycosylation of the cholinesterases [78]. It has been reported that PS1 interacts with AChE, and affects the enzymatic activity and glycosylation of the enzyme [86]. Reelin is another protein involved in regulating synaptic function and plasticity that has altered glycosylation properties in AD.…”