Steven L. Wagner

Decreased alpha-secretase-cleaved amyloid precursor protein as a diagnostic marker for Alzheimer's disease.

The neuropathologic hallmarks of Alzheimers disease (AD) are extracellular plaques and intracellular neurofibrillary tangles. A constituent of senile plaques in AD is β-amyloid, a hydrophobic peptide of 39–43 amino acids1 and a fragment of the amyloid precursor protein (APP). APP can be metabolized by at least two pathways, one of which involves generation of soluble APP by an unidentified enzyme named α-secretase. This cleavage generates α-secretase-cleaved, soluble APP (α–sAPP), which in this investigation was measured by a new assay in cerebrospinal fluid (CSF) from members of a Swedish AD family with a pathogenic mutation at APP670/671 (ref. 2). Family members who carry the mutation and are diagnosed with AD had low levels of α–sAPP (160 ± 48 ng ml−1), with no overlap compared with non-carriers (257 ± 48 ng ml−1). Carriers of the presymptomatic mutation showed intermediate α–sAPP levels. Today there exists no antemortem marker in AD with sufficient sensitivity and specificity, but measurement of α–sAPP represents a new and promising diagnostic marker.

Amyloid production and deposition in mutant amyloid precursor protein and presenilin-1 yeast artificial chromosome transgenic mice.

Dosage imbalance for chromosome 21 in Down syndrome and mutations in the amyloid precursor protein (APP) and presenilin-1 (PS-1) genes in early-onset familial Alzheimers disease (FAD) result in elevated production and deposition of amyloid-β (Aβ) peptides, particularly the 42 amino acid form, Aβ1–42. One difficulty in studying the generation and deposition of Aβ, neuritic abnormalities, synaptic dysfunction, neuronal cell death and dementia that occurs in Alzheimers disease (AD) is the paucity of small animal models. To examine effects of the FAD mutations in vivo, we transferred yeast artificial chromosomes (YACs) containing the entire genomic copy of human APP and/or PS-1 genes harboring FAD mutations into transgenic mice. We now document that a mutant APP YAC transgenic mouse develops Aβ deposits and that this deposition is accelerated when the animals are mated to homozygosity and/or to mutant PS-1 YAC transgenic mice.

Specific patterns of amyloid β-protein precursor isoform secretion and proteolysis in cultured human cells

A characteristic neuropathologic feature of Alzheimer c disease is an abundance of brain-localized neuritic plaques. These plaques are identified as areas of degenerating nerve terminals surrounding cores of aggregated and insoluble fibrils of amyloid β-protein (Aβ). Aβ is generated by proteolytic cleavage of a large precursor protein, the amyloid β-protein precursor (AβPP). In this study, soluble AβPPs (sAβPPs) secreted by human cell lines originating from different tissues were characterized. Various human cell types were shown to secrete different characteristic isoforms of AβPP. Peripheral cells (i.e., fibroblasts and keratinocytes) secreted only the soluble derivative of the 770-amino acid isoform (sAβPP770). In contrast, cells derived from the central and peripheral nervous system (i.e., neumblastoma and glioblastoma) secreted the soluble derivative of the 751-amino acid isoform (sAβPP751), while the 695-amino acid isoform (sAβPP695) was secreted exclusively by neuronal-type cells. We have also dete...