Enhancement of α‐secretase cleavage of amyloid precursor protein by a metalloendopeptidase nardilysin

Abstract

Amyloid-b (Ab) peptide, the principal component of senile plaques in the brains of patients with Alzheimer's disease, is derived from proteolytic cleavage of amyloid precursor protein (APP) by b-and c-secretases. Alternative cleavage of APP by a-secretase occurs within the Ab domain and precludes generation of Ab peptide. Three members of the ADAM (a disintegrin and metalloprotease) family of proteases, ADAM9, 10 and 17, are the main candidates for a-secretases. However, the mechanism that regulates a-secretase activity remains unclear. We have recently demonstrated that nardilysin (EC 3.4.24.61, N-arginine dibasic convertase; NRDc) enhances ectodomain shedding of heparin-binding epidermal growth factor-like growth factor through activation of ADAM17. In this study, we show that NRDc enhances the a-secretase activity of ADAMs, which results in a decrease in the amount of Ab generated. When expressed with ADAMs in cells, NRDc dramatically increased the secretion of a-secretase-cleaved soluble APP and reduced the amount of Ab peptide generated. A peptide cleavage assay in vitro also showed that recombinant NRDc enhances ADAM17-induced cleavage of the peptide substrate corresponding to the a-secretase cleavage site of APP. A reduction of endogenous NRDc by RNA interference was accompanied by a decrease in the cleavage by a-secretase of APP and increase in the amount of Ab generated. Notably, NRDc is clearly expressed in cortical neurons in human brain. Our results indicate that NRDc is involved in the metabolism of APP through regulation of the a-secretase activity of ADAMs, which may be a novel target for the treatment of Alzheimer's disease. Keywords: a disintegrin and metalloprotease proteases, a-secretase, Alzheimer's disease, amyloid-b, ectodomain shedding, nardilysin. Alzheimer's disease (AD), a progressive neurodegenerative disorder, is characterized by a variety of pathological features in the brain such as extracellular senile plaques and intracellular neurofibrillary tangles. The main component of the extracellular senile plaques is amyloid b (Ab) peptide, which is derived from amyloid precursor protein (APP), a type I transmembrane protein, by two sequential proteolytic cleavages. The initial cleavage is mediated by b-secretase, b-site APP-cleaving enzyme 1, at the N-terminus of the Ab domain, which generates a soluble N-terminal fragment (bsecretase-cleaved soluble APP; sAPPb) and a transmembrane C-terminal fragment (C99). C99 is susceptible to a second intramembrane cleavage by c-secretase, releasing the 4-kDa

Reduced neuronal co-localisation of nardilysin and the putative α-secretases ADAM10 and ADAM17 in Alzheimer’s disease and Down syndrome brains

“…Although both NRDc (Bernstein et al 2007;Hiraoka et al 2007) and ADAM10 and ADAM17 (Marcinkiewicz and Seidah 2000;Skovronsky et al 2001;Bernstein et al 2003) have been demonstrated to be expressed in subsets of human cortical neurons, there is as yet no anatomical evidence supporting a co-localisation of NRDc with either of the ADAMs in human brain. Since the abovementioned assumption of altered cellular co-expression of NRDc and ADAMs in AD and DS is a testable hypothesis of considerable importance, we decided to address the following questions: (1) Does NRDc appear to be coexpressed with either ADAM10 or ADAM17 in human brain cortical neurons?…”

“…Firstly, in microarray studies, NRDc mRNA was found to be up-regulated in blood mononuclear cells of AD patients (Maes et al 2007). Secondly, in cell culture experiments it was shown that the enzyme is capable of enhancing the α-secretase activity of ADAMs (a disintegrin and metalloproteases) 10 and 17 (Hiraoka et al 2007). This possibly contributes to reduced generation of amyloidogenic fragments from the amyloid precursor protein (APP).…”

“…Taking into account the putative involvement of NRDc in neuropeptide metabolism and pivotal cellular processes such as neuronal proliferation, differentiation, and migration on the one hand, and the wide neuronal distribution of the enzyme in developing and adult human brain on the other (Bernstein et al 2007;Hiraoka et al 2007), it is of great interest to reveal the actual functional importance of NRDc for normal and diseased central nervous systems (CNS).…”

The Mitochondrial Secret(ase) of Alzheimer's Disease

“…ADAM10 is necessary to reduce AD plaques and improve learning and memory in mouse models [65,66]. Overexpression or upregulation of α-secretase activity by agents like copper [67], muscarinic agonists, anti-cholesterol agents, and nonsteroidal anti-inflammatory drugs (NSAIDs) [63] has been proposed as a potential AD therapeutic because: 1) α-secretase activity precludes the generation of Aβ by β-secretase cleavage and would therefore increase production of the non-amyloidogenic, potentially neuroprotective cleavage products of AβPP [68] and 2) reports of reduced levels of the α-secretase and its cleavage product (sAβPPα) in platelets and cerebrospinal fluid of AD subjects have been made [69][70][71]. This reduction in an α-secretase cleavage product raises questions of whether Aβ overproduction is due directly to rises in β-secretase activity or indirectly through depressed α-secretase activity that makes AβPP more available for Aβ-generating cleavage, and it has potential as a potential biomarker because of its correlation with pre-clinical and clinical stages in patients with Swedish mutation AD [71].…”

Nardilysin controls intestinal tumorigenesis through HDAC1/p53–dependent transcriptional regulation

“…Although NRDC is a soluble cytosolic protein with no apparent signal peptide, a portion of NRDC is secreted through an unconventional secretory pathway and distributed on the cell surface (7)(8)(9). We originally identified NRDC as a cell-surface receptor for heparin-binding epidermal growth factor-like growth factor (HB-EGF) (8), and our subsequent studies have demonstrated that NRDC enhances ectodomain shedding of multiple membrane proteins including HB-EGF (10)(11)(12)(13)(14). For instance, forced expression of NRDC or administration of the NRDC protein enhances ectodomain shedding of TNF-α through the activation of a disintegrin and metalloproteinase 17 (ADAM17) (12).…”