title: Fibulin-5 is a novel binding protein for extracellular superoxide dismutase.
abstract: The extracellular superoxide dismutase (ecSOD) plays an important role in atherosclerosis and endothelial function by modulating levels of the superoxide anion (O2*-) in the extracellular space. Although heparan sulfate proteoglycan is an important ligand for ecSOD, little is known about other biological binding partners of ecSOD. The goal of this study was to identify novel proteins that interact with ecSOD. A yeast two-hybrid screening of a human aorta cDNA library using ecSOD as bait identified fibulin-5 as a predominant binding protein for ecSOD. Further analysis showed that the binding domain of ecSOD within fibulin-5 mapped to its C-terminal domain. In vitro pulldown assays and coimmunoprecipitation analysis further confirmed that ecSOD interacts with fibulin-5 in vitro and in vivo. Studies using fibulin-5-/- mice indicated that fibulin-5 is required for binding of ecSOD to vascular tissue. Importantly, the decrease in tissue-bound ecSOD levels in aortas from fibulin-5-/- mice was associated with an increase in vascular O2*- levels. Furthermore, immunohistochemical analysis using ApoE-/- mice suggested a codistribution of ecSOD and fibulin-5 in atherosclerotic vessels. In summary, we provide in this study the first evidence that the ecSOD-fibulin-5 interaction is required for ecSOD binding to vascular tissues, thereby regulating vascular O2*- levels. This interaction may represent a novel mechanism for controlling vascular redox state in the extracellular space in various cardiovascular diseases such as atherosclerosis and hypertension in which oxidative stress is increased.
authors.affiliation: Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, Ga 30322, USA.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Nguyen
authors.forename: Shinichi
authors.initials: S
authors.lastname: Itoh
authors.forename: Viktoria
authors.initials: V
authors.lastname: Jeney
authors.forename: Hiromi
authors.initials: H
authors.lastname: Yanagisawa
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Fujimoto
authors.forename: Masuko
authors.initials: M
authors.lastname: Ushio-Fukai
authors.forename: Tohru
authors.initials: T
authors.lastname: Fukai
mesh_terms: D000818:Animals; D001011:Aorta / Q000378:metabolism*; D001018:Aortic Diseases / Q000235:genetics / Q000378:metabolism; D001057:Apolipoproteins E / Q000172:deficiency / Q000235:genetics; D001161:Arteriosclerosis / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D016466:CHO Cells; D002474:Cell-Free System; D002478:Cells, Cultured / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D004331:Drosophila melanogaster; D045604:Extracellular Fluid / Q000201:enzymology*; D016326:Extracellular Matrix Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015723:Gene Library; D006801:Humans; D008024:Ligands; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018384:Oxidative Stress; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D014162:Transfection; D020798:Two-Hybrid System Techniques
chemical_list: D001057:Apolipoproteins E; D016326:Extracellular Matrix Proteins; C492373:FBLN5 protein, human; C120769:Fbln5 protein, mouse; D008024:Ligands; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D013481:Superoxides; C441642:SOD3 protein, human; C499090:Sod3 protein, mouse; D013482:Superoxide Dismutase