title: ERK1-independent α-secretase cut of β-amyloid precursor protein via M1 muscarinic receptors and PKCα/ε.
abstract: The amyloid precursor protein (βAPP) undergoes several proteolytic cleavages. While β- and γ-secretases are responsible for the production of the 40-43 amino-acid long amyloid β peptide (Aβ), the α-secretase cut performed by the disintegrins ADAM10 and ADAM17, occurs in the middle of the Aβ sequence, thereby preventing its formation and leading to the secretion of the large sAPPα neuroprotective fragment. Here we showed that a series of M1 muscarinic receptor agonists dose-dependently stimulated sAPPα secretion without interfering with βAPP subcellular distribution. Carbachol- and PDBu-induced sAPPα secretions were blocked by the general PKC inhibitor GF109203X. We established that HEK293 and rhabdhomyosarcoma cells overexpressing constitutively active (CA) PKCα or PKCε secrete increased amounts of sAPPα while those expressing PKCδ were unable to modify sAPPα recovery. Conversely, the overexpression of PKCα or PKCε dominant negative (DN) constructs abolished PDBU-stimulated sAPPα secretion, whereas DN-PKCδ remained inert. In agreement, PKCα knockout lowered sAPPα recovery in primary cultured fibroblasts. We also demonstrated that the regulated α-secretase processing of βAPP is not controlled by the Extracellular-Regulated Kinase-1/MAP-ERK Kinase (ERK1/MEK) cascade and likely does not require ADAM17 phosphorylation on its threonine735 residue. Because the muscarinic-dependent α-secretase-like processing of PrP(c) is fully dependent on ADAM17 phosphorylation on its threonine735 residue by ERK1, these results indicate that a single extracellular signal triggers ADAM17-dependent regulated cleavages of βAPP and PrP(c) through distinct signalling cascades. This opens new potential therapeutic strategies aimed, in the context of Alzheimer's disease, at selectively activating ADAM17 towards βAPP without affecting the cleavages of its numerous other substrates.
authors.affiliation: Université de Nice-Sophia-Antipolis, Institut de Neuro-Médecine Moléculaire, Unité Mixte de Recherche, 6097 Centre National de la Recherche Scientifique, Equipe labellisée Fondation pour la Recherche Médicale, 660 route des lucioles, Sophia-Antipolis, 06560 Valbonne, France.
authors.forename: Moustapha
authors.initials: M
authors.lastname: Cisse
authors.forename: Ursula
authors.initials: U
authors.lastname: Braun
authors.forename: Michael
authors.initials: M
authors.lastname: Leitges
authors.forename: Abraham
authors.initials: A
authors.lastname: Fisher
authors.forename: Gilles
authors.initials: G
authors.lastname: Pages
authors.forename: Frédéric
authors.initials: F
authors.lastname: Checler
authors.forename: Bruno
authors.initials: B
authors.lastname: Vincent
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism; D000072198:ADAM17 Protein; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006801:Humans; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051571:Protein Kinase C-alpha / Q000378:metabolism*; D051744:Protein Kinase C-epsilon / Q000378:metabolism*; D043643:Receptor, Muscarinic M1 / Q000819:agonists / Q000378:metabolism*
chemical_list: D016564:Amyloid beta-Protein Precursor; D043643:Receptor, Muscarinic M1; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon; D053829:Amyloid Precursor Protein Secretases; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; C000606463:Adam17 protein, mouse