title: PEX7 and EBP50 target iNOS to the peroxisome in hepatocytes.
abstract: iNOS localizes to both the cytosol and peroxisomes in hepatocytes in vitro and in vivo. The structural determinants for iNOS localization are not known. One plausible mechanism for iNOS localization to the peroxisome is through the interaction with peroxisomal import proteins PEX5 or PEX7. siRNA knockdown of PEX7 reduced iNOS colocalization with the peroxisomal protein PMP70. Proteomic studies using MALDI-MS identified iNOS association with the 50-kD ezrin binding PDZ protein (EBP50). Confocal microscopy studies and immunoelectron microscopy confirmed iNOS association with EBP50, with greatest colocalization occurring at 8h of cytokine exposure. EBP50 associated with peroxisomes in a PEX5 and PEX7-dependent manner. iNOS localization to peroxisomes was contingent on EBP50 expression in LPS-treated mice. Thus, iNOS targeting to peroxisomes in hepatocytes involves interaction with PEX7 and EBP50. The targeting of iNOS protein to the peroxisome may shift the balance of metabolic processes that rely on heme proteins susceptible to modification by radical oxygen and nitrogen radicals.
authors.affiliation: Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA. loughranp@upmc.edu
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Loughran
authors.forename: Donna B
authors.initials: DB
authors.lastname: Stolz
authors.forename: Stacey R
authors.initials: SR
authors.lastname: Barrick
authors.forename: David S
authors.initials: DS
authors.lastname: Wheeler
authors.forename: Peter A
authors.initials: PA
authors.lastname: Friedman
authors.forename: Richard A
authors.initials: RA
authors.lastname: Rachubinski
authors.forename: Simon C
authors.initials: SC
authors.lastname: Watkins
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Billiar
mesh_terms: D000818:Animals; D022781:Hepatocytes / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D008099:Liver / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D000074437:Peroxisomal Targeting Signal 2 Receptor; D020675:Peroxisomes / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
chemical_list: D000074437:Peroxisomal Targeting Signal 2 Receptor; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse