title: Expression of an enzymically active glycosylphosphatidylinositol-anchored form of neutral endopeptidase (EC 3.4.24.11) in Cos-1 cells.
abstract: Neutral endopeptidase (EC 3.4.24.11, NEP) is a type-II integral membrane protein found in a wide variety of cell types. We previously produced a secreted form of the enzyme by deletion of the cytoplasmic and transmembrane domains and in-frame fusion of the cleavable signal peptide of pro-opiomelanocortin [Lemay, Waksman, Roques, Crine and Boileau (1989) J. Biol. Chem. 264, 15620-15623]. Here we have used this secreted form of NEP and fused to it the glycosylphosphatidylinositol (GPI)-anchor attachment signal of decay-accelerating factor to produce a GPI-anchored form. Expression of this chimeric form in Cos-1 cells resulted in cell-surface activity. This activity could be released from the cell surface by phosphatidylinositol-specific phospholipase C and radiolabelling studies showed that the protein could incorporate [3H]ethanolamine, indicating that the enzyme was GPI-anchored. The Km value, using [D-Ala2,Leu5]enkephalin as substrate, of GPI-anchored NEP (62 +/- 5 microM) was comparable with that of wild-type NEP (70 +/- 4 microM), as were the sensitivities to the inhibitors phosphoramidon and thiorphan. However, pulse-chase studies showed that the biosynthesis and cell-surface delivery of GPI-anchored NEP was delayed compared with that of the wild-type transmembrane form of NEP. These results suggest a lower rate of biosynthesis and/or cellular transport for GPI-anchored NEP compared with its transmembrane counterpart.
authors.affiliation: Département de Biochimie, Faculté de Médecine, Université de Montréal, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Howell
authors.forename: C
authors.initials: C
authors.lastname: Lanctôt
authors.forename: G
authors.initials: G
authors.lastname: Boileau
authors.forename: P
authors.initials: P
authors.lastname: Crine
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D008969:Molecular Sequence Data; D015260:Neprilysin / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins / Q000235:genetics
chemical_list: D017261:Glycosylphosphatidylinositols; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins; D015260:Neprilysin