title: Furin proteolytically processes the heparin-binding region of extracellular superoxide dismutase.
abstract: Extracellular superoxide dismutase (EC-SOD) is an antioxidant enzyme that attenuates brain and lung injury from oxidative stress. A polybasic region in the carboxyl terminus distinguishes EC-SOD from other superoxide dismutases and determines EC-SOD's tissue half-life and affinity for heparin. There are two types of EC-SOD that differ based on the presence or absence of this heparin-binding region. It has recently been shown that proteolytic removal of the heparin-binding region is an intracellular event (Enghild, J. J., Thogersen, I. B., Oury, T. D., Valnickova, Z., Hojrup, P., and Crapo, J. D. (1999) J. Biol. Chem. 274, 14818-14822). By using mammalian cell lines, we have now determined that removal of the heparin-binding region occurs after passage through the Golgi network but before being secreted into the extracellular space. Specific protease inhibitors and overexpression of intracellular proteases implicate furin as a processing protease. In vitro experiments using furin and purified EC-SOD suggest that furin proteolytically cleaves EC-SOD in the middle of the polybasic region and then requires an additional carboxypeptidase to remove the remaining lysines and arginines. A mutation in Arg(213) renders EC-SOD resistant to furin processing. These results indicate that furin-dependent processing of EC-SOD is important for determining the tissue distribution and half-life of EC-SOD.
authors.affiliation: National Jewish Medical and Research Center, Denver, Colorado 80206, USA. BowlerR@njc.org
authors.forename: Russell P
authors.initials: RP
authors.lastname: Bowler
authors.forename: Mike
authors.initials: M
authors.lastname: Nicks
authors.forename: Dorte Aa
authors.initials: DA
authors.lastname: Olsen
authors.forename: Ida B
authors.initials: IB
authors.lastname: Thøgersen
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Valnickova
authors.forename: Peter
authors.initials: P
authors.lastname: Højrup
authors.forename: Alex
authors.initials: A
authors.lastname: Franzusoff
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Enghild
authors.forename: James D
authors.initials: JD
authors.lastname: Crapo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000737:chemistry; D015153:Blotting, Western; D020126:Brefeldin A / Q000494:pharmacology; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D045683:Furin; D005998:Glycine / Q000737:chemistry; D006056:Golgi Apparatus / Q000378:metabolism*; D006493:Heparin / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D018384:Oxidative Stress; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D013381:Subtilisins / Q000737:chemistry / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured
chemical_list: D004791:Enzyme Inhibitors; D011500:Protein Synthesis Inhibitors; D020126:Brefeldin A; D006493:Heparin; D001120:Arginine; D013482:Superoxide Dismutase; D013381:Subtilisins; D045683:Furin; D005998:Glycine