title: Ectodomain shedding of the neural recognition molecule CHL1 by the metalloprotease-disintegrin ADAM8 promotes neurite outgrowth and suppresses neuronal cell death.
abstract: The neural cell adhesion molecule "close homologue of L1," termed CHL1, has functional importance in the nervous system. CHL1 is expressed as a transmembrane protein of 185 kDa, and ectodomain shedding releases soluble fragments relevant for its physiological function. Here we describe that ADAM8, a member of the family of metalloprotease disintegrins cleaves a CHL1-Fc fusion protein in vitro at two sites corresponding to release of the extracellular domain of CHL1 in fibronectin (FN) domains II (125 kDa) and V (165 kDa), inhibited by batimastat (BB-94). Cleavage of CHL1-Fc in the 125-kDa fragment was not detectable under non-reducing conditions arguing that cleavage resulting in the 165-kDa fragment is more relevant in releasing soluble CHL1 in vivo. In cells transfected with full-length ADAM8, membrane proximal cleavage of CHL1 was similar and not stimulated by phorbol ester 12-O-tetradecanoylphorbol-13-acetate and pervanadate. No cleavage of CHL1 was observed in cells expressing either inactive ADAM8 with a Glu330 to Gln exchange (EQ-A8), or active ADAM10 and ADAM17. Consequently, processing of CHL1 was hardly detectable in brain extracts of ADAM8-deficient mice but enhanced in a neurodegenerative mouse mutant. CHL1 processed by ADAM8 in supernatants of COS-7 cells and in co-culture with cerebellar granule neurons was very potent in stimulating neurite outgrowth and suppressing neuronal cell death, not observed in cells co-transfected with CHL1/EQ-A8, CHL1/ADAM10, or CHL1/ADAM17. Taken together, we propose that ADAM8 plays an important role in physiological and pathological cell interactions by a specific release of functional CHL1 from the cell surface.
authors.affiliation: Entwicklungsbiologie & Molekulare Pathologie, W7, Universität Bielefeld, 33501 Bielefeld, Germany.
authors.forename: Silvia
authors.initials: S
authors.lastname: Naus
authors.forename: Melanie
authors.initials: M
authors.lastname: Richter
authors.forename: Dirk
authors.initials: D
authors.lastname: Wildeboer
authors.forename: Marcia
authors.initials: M
authors.lastname: Moss
authors.forename: Melitta
authors.initials: M
authors.lastname: Schachner
authors.forename: Jörg W
authors.initials: JW
authors.lastname: Bartsch
mesh_terms: D051722:ADAM Proteins; D000818:Animals; D015703:Antigens, CD / Q000502:physiology*; D002450:Cell Communication / Q000502:physiology; D016923:Cell Death / Q000502:physiology; D008565:Membrane Proteins / Q000502:physiology*; D008666:Metalloendopeptidases / Q000502:physiology*; D051379:Mice; D009154:Mutation; D016501:Neurites / Q000502:physiology / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D010446:Peptide Fragments; D017434:Protein Structure, Tertiary
chemical_list: D015703:Antigens, CD; D008565:Membrane Proteins; D010446:Peptide Fragments; D051722:ADAM Proteins; C489402:Adam8 protein, mouse; D008666:Metalloendopeptidases