Novel precursor of Alzheimer's disease amyloid protein shows protease inhibitory activity

Abstract

Alzheimer's disease is characterized by cerebral deposits of amyloid beta-protein (AP) as senile plaque core and vascular amyloid, and a complementary DNA encoding a precursor of this protein (APP) has been cloned from human brain. From a cDNA library of a human glioblastoma cell line, we have isolated a cDNA identical to that previously reported, together with a new cDNA which contains a 225-nucleotide insert. The sequence of the 56 amino acids at the N-terminal of the protein deduced from this insert is highly homologous to the basic trypsin inhibitor family, and the lysate from COS-1 cells transfected with the longer APP cDNA showed an increased inhibition of trypsin activity. Partial sequencing of the genomic DNA encoding APP showed that the 225 nucleotides are located in two exons. At least three messenger RNA species, apparently transcribed from a single APP gene by alternative splicing, were found in human brain. We suggest that protease inhibition by the longer APP(s) could be related to aberrant APP catabolism.

Retinoic acid induced differentiated neuroblastoma cells show increased expression of the βA4 amyloid gene of Alzheimer's disease and an altered splicing pattern

“…Proteolytic processing of these APP proteins in the Golgi apparatus leads to the secretion of the extracellular part the APP protein isoforms [8]. proteins differ from APP69s by one or two additional domains of 56 or 56 and 19 amino acids [12]. Both domains are encoded by two adjacent exons on the PAD gene, namely exon 7 (168 bp) and exon 8 (57 bp) [ 12,131.…”

“…proteins differ from APP69s by one or two additional domains of 56 or 56 and 19 amino acids [12]. Both domains are encoded by two adjacent exons on the PAD gene, namely exon 7 (168 bp) and exon 8 (57 bp) [ 12,131. The expression of the PAD gene is ubiquitous, being highest in brain and kidney [lo].…”

Aberrant proteolysis of the β‐amyloid precursor protein in familial Alzheimer's disease lymphoblastoid cells

“…The molecularweight-markers used in SDYPAGE were 21 2-kDa myosin. 170-kDa P-galactosidase, 76-kDa transferrin, 53-kDa glutamic dehydrogenase, 33-kDa carbonic anhydrase, 24-kDa soy bean trypsin inhibitor, 16-kDa lysozymc, 14-kDa myoglobin I+II, 8.2-kDa myoglobin I and 3.5-kDa glucagon (Bio Rad. Pharmacia and Sigma).…”

Alpha 2‐macroglobulin synthesis in interleukin‐6‐stimulated human neuronal (SH‐SY5Y neuroblastoma) cells Potential significance for the processing of Alzheimer β‐amyloid precursor protein

“…3, lanes 1,5,9). This heterogeneity has previously been shown to be due to the facts first that the APP hn mRNA is differentially spliced into 3 major mRNA forms [6,9,23], and second that the APP protein is subjected to intracellular processing including Iv-, Oglycosylation, and thyorosine sulfation [I I]. Secretion 'of the major N-terminal part of APP is achieved by proteolytic cleavage of the mature transmembrane APP molecule [12] resulting in secreted APP forms in the molecular weight range between 98 kRa and 123 kDa (Fig.…”

“…Proteases and their inhibitors may contribute to pathogenic events. In Alzhcimer's disease (AD), proteases and their inhibitors seem to be of particular importance: (i) the proteases cathepsin B and D [4] as well as the proteinase inhibitor alpha I-antichymotrypsin [S] have been found to be constituents of AD senile plaques; (ii) two forms (APP751 and the APPvo) of the Alzheimer @G4-amyloid precursor protein (APP) are Kunitz-type proteinase inhibitors [6,7, for reviews see 7,8]; (iii) by investigating APP synthesis in cultured cells it has been found that secretion of (the large N-terminal part of) APP is the result of a proteolytic cleavage C-terminal to residue 16 of the @A4 part of the mature transmembrane APP [g-13]. mation of AD senile plaques 1321.…”