title: Cytosolic localization of NADH cytochrome b₅ oxidoreductase (Ncb5or).
abstract: Acyl-CoA desaturation in the endoplasmic reticulum (ER) membrane depends on cytosolic NADH or NADPH, whereas NADPH in the ER lumen is utilized by prereceptor glucocorticoid production. It was assumed that NADH cytochrome b5 oxidoreductase (Ncb5or) might connect Acyl-CoA desaturation to ER luminal redox. We aimed to clarify the ambiguous compartmentalization of Ncb5or and test the possible effect of stearoyl-CoA on microsomal NADPH level. Amino acid sequence analysis, fluorescence microscopy of GFP-tagged protein, immunocytochemistry, and western blot analysis of subcellular fractions unequivocally demonstrated that Ncb5or, either endogenous or exogenous, is localized in the cytoplasm and not in the ER lumen in cultured cells and liver tissue. Moreover, the involvement of ER-luminal reducing equivalents in stearoyl-CoA desaturation was excluded.
authors.affiliation: Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
authors.forename: Veronika
authors.initials: V
authors.lastname: Zámbó
authors.affiliation: Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
authors.forename: Mónika
authors.initials: M
authors.lastname: Tóth
authors.affiliation: 2nd Department of Pathology, Semmelweis University, Budapest, Hungary.
authors.forename: Krisztina
authors.initials: K
authors.lastname: Schlachter
authors.affiliation: Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Szelényi
authors.affiliation: Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
authors.forename: Farkas
authors.initials: F
authors.lastname: Sarnyai
authors.affiliation: 2nd Department of Pathology, Semmelweis University, Budapest, Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Lotz
authors.affiliation: Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
authors.forename: Miklós
authors.initials: M
authors.lastname: Csala
authors.affiliation: Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
authors.forename: Éva
authors.initials: É
authors.lastname: Kereszturi
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D019295:Computational Biology; D042966:Cytochrome-B(5) Reductase / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006801:Humans; D008861:Microsomes / Q000378:metabolism; D010084:Oxidation-Reduction; D021381:Protein Transport
chemical_list: D000214:Acyl Coenzyme A; C017725:stearoyl-coenzyme A; D042966:Cytochrome-B(5) Reductase
keywords: endoplasmic reticulum; fatty acid desaturation; glucocorticoid; pyridine nucleotides; redox state