title: Constitutive shedding of the amyloid precursor protein ectodomain is up-regulated by tumour necrosis factor-alpha converting enzyme.
abstract: The amyloid precursor protein (APP) of Alzheimer's disease is a transmembrane protein that is cleaved within its extracellular domain, liberating a soluble N-terminal fragment (sAPP alpha). Putative mediators of this process include three members of the ADAM (a disintegrin and metalloprotease) family, ADAM9, ADAM10 and ADAM17/TACE (tumour necrosis factor-alpha converting enzyme). Tumour necrosis factor-alpha protease inhibitor (TAPI-1), an inhibitor of ADAMs, reduced constitutive and muscarinic receptor-stimulated sAPP alpha release in HEK-293 cells stably expressing M3 muscarinic receptors. However, the former was less sensitive to TAPI-1 (IC(50)=8.09 microM) than the latter (IC(50)=3.61 microM), suggesting that these processes may be mediated by different metalloproteases. Constitutive sAPP alpha release was increased several-fold in cells transiently transfected with TACE, and this increase was proportional to TACE expression. In contrast, muscarinic-receptor-activated sAPP alpha release was not altered in TACE transfectants. TACE-dependent constitutive release of co-transfected APP(695) was inhibited by TAPI-1 with an IC(50) of 0.92 microm, a value significantly lower than the IC(50)s for inhibition of either constitutive or receptor-regulated sAPP alpha shedding mediated by endogenous secretases. The results indicate that TACE is capable of catalysing constitutive alpha-secretory cleavage of APP, but it is likely that additional members of the ADAM family mediate endogenous constitutive and receptor-coupled release of sAPP alpha in HEK-293 cells.
authors.affiliation: Department of Pathology and Laboratory Medicine, Boston University School of Medicine, 85 East Newton Street, Rm. M1007, Boston, MA 02118, USA. bslack@bu.edu
authors.forename: B E
authors.initials: BE
authors.lastname: Slack
authors.forename: L K
authors.initials: LK
authors.lastname: Ma
authors.forename: C C
authors.initials: CC
authors.lastname: Seah
mesh_terms: D051722:ADAM Proteins; D000072198:ADAM17 Protein; D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D010450:Endopeptidases / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D016564:Amyloid beta-Protein Precursor; D004151:Dipeptides; D006877:Hydroxamic Acids; C092152:N-((2-(hydroxyaminocarbonyl)methyl)-4-methylpentanoyl)-3-(2'-naphthyl)alanylalanine, 2-aminoethylamide; D011480:Protease Inhibitors; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human