Detection of soluble forms of the β-amyloid precursor protein in human plasma

• Published in: Biochemical and biophysical research communications Vol. 167; no. 3; pp. 1094 - 1101
• Main Authors: Podlisny, Marcia B., Mammen, Andrew L., Schlossmacher, Michael G., Palmert, Mark R., Younkin, Steven G., Selkoe, Dennis J.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 30.03.1990; Elsevier
• Subjects: Aged; Aged, 80 and over; Alzheimer Disease - blood; Amyloid - blood; Amyloid - isolation & purification; Amyloid beta-Protein Precursor; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Biomarkers - blood; Chromatography, Affinity; Down Syndrome - blood; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Humans; Immunoblotting; Middle Aged; Miscellaneous; Molecular Weight; plasma; Protease Inhibitors - blood; Protein Precursors - blood; Protein Precursors - isolation & purification; Proteins; Reference Values; Solubility; APP; AD; KPI; CSF; APPx-y; AβP; DS; Human; Molecular form; Alzheimer disease; Blood plasma; Characterization; Proteins; Precipitation; Affinity chromatography; Deletion; Immunoblotting assay; Amyloid; Biosynthesis precursor; Detection
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/0006-291X(90)90635-Z

A ∼40-residue fragment of the β-amyloid precursor protein (APP) is progressively deposited in the extracellular spaces of brain and blood vessels in Alzheimer's disease (AD), Down's syndrome and aged normal subjects. Soluble, truncated forms of APP lacking the carboxyl terminus are normally secreted from cultured cells expressing this protein and are found in cerebrospinal fluid. Here, we report the detection of a similar soluble APP isoform in human plasma. This ∼125 kDa protein, which was isolated from plasma by Affi-Gel Blue chromatography or dialysis-induced precipitation, comigrates with the larger of the two major soluble APP forms present in spinal fluid and contains the Kunitz protease inhibitor insert. It thus derives from the APP751 and APP770 precursors; a soluble form of APP695 has not yet been detected in plasma. The ∼125 kDa plasma form lacks the C-terminal region and is unlikely to serve as a precursor for the β-protein that forms the amyloid in AD.