Expression of Presenilin 1 and 2 (PS1 and PS2) in Human and Murine Tissues

Abstract

Mutations in genes encoding related proteins, termed presenilin 1 (PS1) and presenilin 2 (PS2), are linked to the majority of cases with early-onset familial Alzheimer's disease (FAD). To clarify potential function(s) of presenilins and relationships of presenilin expression to pathogenesis of AD, we examined the expression of PS1 and PS2 mRNA and PS1 protein in human and mouse. Semi-quantitative PCR of reverse-transcribed RNA (RT-PCR) analysis revealed that PS1 and PS2 mRNA are expressed ubiquitously and at comparable levels in most human and mouse tissues, including adult brain. However, PS1 mRNA is expressed at significantly higher levels in developing brain. In situ hybridization studies of mouse embryos revealed widespread expression of PS1 mRNA with a neural expression pattern that, in part, overlaps that reported for mRNA encoding specific Notch homologs. In situ hybridization analysis in adult mouse brain revealed that PS1 and PS2 mRNAs are enriched in neurons of the hippocampal formation and entorhinal cortex. Although PS1 and PS2 mRNA are expressed most prominently in neurons, lower but significant levels of PS1 and PS2 transcripts are also detected in white matter glial cells. Moreover, cultured neurons and astrocytes express PS1 and PS2 mRNAs. Using PS1-specific antibodies in immunoblot analysis, we demonstrate that PS1 accumulates as approximately 28 kDa N-terminal and approximately 18 kDa C-terminal fragments in brain. Immunocytochemical studies of mouse brain reveal that PS1 protein accumulates in a variety of neuronal populations with enrichment in somatodendritic and neuropil compartments.

Cellular distribution of γ-secretase subunit nicastrin in the developing and adult rat brains

“…Consistent with previous reports [3,12,27,28,29,53], we find that PS1 is distributed widely in the adult rat brain. Additionally, our double labeling experiments showed that PS1 is coexpressed with nicastrin in almost all brain regions investigated in the present study, leading to the suggestion that nicastrin most likely acts as an integral component of the γ-secretase complex in the brain rather than mediating any effects of its own.…”

“…In agreement with earlier reports [3,12,27,28,29,53], PS1-immunoreactive neurons and fibers were distributed throughout the brain including the septal/diagonal band complex, nucleus basalis of Meynert, striatum, cerebral cortex, hippocampus, amygdala, thalamus, hypothalamus, median eminence, brainstem motor nuclei and cerebellar Purkinje cells (Figs. 5 and 6).…”

“…The nicastrin and PS1 antisera used in the present study have been previously characterized [29,30,51]. The specificity of antisera is further confirmed by our immunoblotting experiment, which showed that nicastrin antiserum essentially reacted with one major band of approximately 120 kDa corresponding to the mature complex glycosylated forms of the protein in all brain regions examined.…”

“…Adult male rats (225-275 g) and postnatal rats from different developmental stages i.e., postnatal day 1 (P1), P7 and P21 were housed and maintained in accordance with the University of Alberta Policy on the handling and treatment of laboratory animals. The characterization of a polyclonal nicastrin antiserum raised against synthetic peptide corresponding to residues 689-709 (SP718) and a polyclonal PS1 antisera raised against N-terminal (PS1 NT ) fragment has been described previously [29,30,48]. Commercially available goat polyclonal nicastrin antiserum (N-19) was purchased from SantaCruz Biotechnology Inc. (California, USA).…”

Characterization of presenilin complexes from mouse and human brain using Blue Native gel electrophoresis reveals high expression in embryonic brain and minimal change in complex mobility with pathogenic presenilin mutations

“…High levels of PS complex were detected in mouse embryonic brain consistent with high expression of PS1 in embryogenesis and supporting an important role for PS in development, presumably due to its involvement in the Notch signalling system [53]. Indeed studies with PS1 knockout mouse embryos demonstrated severe neural and skeletal defects and PS1/PS2 double knockouts display a severe phenotype resembling Notch gene knockout [3].…”