Altered Processing of Amyloid Precursor Protein in Cells Undergoing Apoptosis

Abstract

Altered proteolysis of amyloid precursor protein is an important determinant of pathology development in Alzheimer's disease. Here, we describe the detection of two novel fragments of amyloid precursor protein in H4 neuroglioma cells undergoing apoptosis. Immunoreactivity of these 25–35 kDa fragments to two different amyloid precursor protein antibodies suggests that they contain the amyloid-β region and an epitope near the C-terminus of amyloid precursor protein. Generation of these fragments is associated with cleavage of caspase-3 and caspase-7, suggesting activation of these caspases. Studies in neurons undergoing DNA damage-induced apoptosis also showed similar results. Inclusion of caspase inhibitors prevented the generation of these novel fragments, suggesting that they are generated by a caspase-dependent mechanism. Molecular weight prediction and immunoreactivity of the fragments generated suggested that such fragments could not be generated by cleavage at any previously identified caspase, secretase, or calpain site on amyloid precursor protein. Bioinformatic analysis of the amino acid sequence of amyloid precursor protein revealed that fragments fitting the observed size and immunoreactivity could be generated by either cleavage at a novel, hitherto unidentified, caspase site or at a previously identified matrix metalloproteinase site in the extracellular domain. Proteolytic cleavage at any of these sites leads to a decrease in the generation of α-secretase cleaved secreted APP, which has both anti-apoptotic and neuroprotective properties, and thus may contribute to neurodegeneration in Alzheimer's disease.

Fendiline inhibits proliferation and invasion of pancreatic cancer cells by interfering with ADAM10 activation and β-catenin signaling

“…Our studies have shown that inhibition of ADAM10, which is established as the -secretase that constitutively cleaves APP, interferes with APP proteolysis [ 19 ]. APP is a transmembrane protein, which is cleaved by α, β and γ-seceretases to generate fragments with variable cellular functions [ 55 - 57 ]. Since fendiline seems to inhibit ADAM10, and because APP is known to play a role in PDAC cell proliferation [ 19 ], we examined if cells treated with fendiline show alterations in APP.…”

Free d-aspartate triggers NMDA receptor-dependent cell death in primary cortical neurons and perturbs JNK activation, Tau phosphorylation, and protein SUMOylation in the cerebral cortex of mice lacking d-aspartate oxidase activity

“…APP and its proteolytic products are implicated in both normal nervous system function and Alzheimer's disease pathogenesis (Selkoe and Hardy, 2016). APP processing and Aβ peptide production are promoted by factors including NMDAR activation (Bordji et al, 2010;Hoey et al, 2009), JNK activation (Mazzitelli et al, 2011;Triaca et al, 2016), and cell death (Fiorelli et al, 2013), which are all biochemical and cerebral features of Ddo −/− aged brain. Interestingly, we observed increased age-dependent cortical immunostaining of APP in neuron cell soma of these mutants.…”

Decreasing or increasing heat shock protein 72 exacerbates or attenuates heat‐induced cell death, respectively, in rat hypothalamic cells

“…Although Annexin is indeed for apoptosis, PI also marks apoptotic cells [29] . This is evident in our present results in Figs.…”