Processing of Wild‐Type and Mutant Familial Alzheimer’s Disease‐Associated Presenilin‐1 in Cultured Neurons

Abstract

Mutations of presenilin (PS)-1, an endoplasmic reticulum/Golgi transmembrane protein, have been associated with early-onset familial Alzheimer's disease (FAD). In mammalian brain, PS1 exists primarily as its processed fragments; however, the role of this cleavage event in PS1 function remains unclear. Although some investigators have shown that mutant PS1 processing is unaltered (with the exception of PS1-⌬E9, which lacks the cleavage site) in stably transfected cells and PS1-FAD transgenic mice, other investigators have reported altered FAD mutant PS1 and PS2 protein processing in transiently transfected cells and human FAD patients. The present study uses recombinant replication-defective adenoviral vectors to transiently express wild-type (WT ) or mutant PS1 in various cells, including primary cultured hippocampal neurons. We show that in contrast to PS1-WT, overexpression of mutant PS1 results in an increased ratio of mutant holoprotein to endoproteolytic products that is dependent on cell type and differentiation state. In addition, mutant PS1 overexpression leads to an increase in caspase-type protease derived fragments above that seen with PS1-WT overexpression. Furthermore, overexpression of at least one mutant significantly alters the processing of coexpressed PS1-WT, suggesting that mutant PS1 may affect PS1-WT function. These findings suggest that a defect in PS1 holoprotein stability may be a general defect seen in cells expressing mutant PS1, especially neuronal cells, and may play a critical role in the pathogenesis of FAD. Key Words: Presenilin-Alzheimer's disease -Proteolytic processing-Recombinant adenoviral vector.

Impaired neurogenesis is an early event in the etiology of familial Alzheimer's disease in transgenic mice

“…Among GSK3's numerous substrates are PS1, β‐catenin, tau, and kinesin‐I light chains (KLC; Takashima et al, 1998; Tesco and Tanzi, 2000; Morfini et al, 2002b; for review see Frame and Cohen, 2001). Previous studies suggest that FAD‐linked PS1 mutations affect GSK3 kinase activity in transfected cell lines (Takashima et al, 1998; Weihl et al, 1999a, b). Importantly, these kinases and phosphatases are known to inhibit fast axonal transport (Morfini et al, 2002a, b).…”

Morphological Change by Overexpression of D385A Dominant Negative Presenilin 1 in Human Neuroblastoma SH-SY5Y Cells

“…In addition, processing conditions of PS1 are different in various cells (10). Thus, processing conditions and functions of PS1 in neurite formation are dependent on cell type and differentiation state.…”

Lentiviral Vector-Based Models of Amyloid Pathology: From Cells to Animals

“…In transduced rat neuronal cells in addition to the expected uncleaved ∆9 mutant band, a smaller immunoreactive fragment is also detected. A similar fragment has been shown to be produced by alternative processing of rat PS1 in rat neurons and in primary rat neuronal cultures infected with adenoviral vector expressing the PS1∆9 mutant [28,38]. Results in Fig.…”

“…APP and PS1 have been expressed in primary neuronal cells using adenoviral vectors [28] and Semliki forest viral (SFV) vectors [29], both of which are transient systems that perturb the cells by initiating cell death [10,30]. On the contrary, lentiviral vectors are stably integrated into the genome of the cell and the expression of the delivered gene continues with minimal perturbation of the cells [15].…”