title: Intracellular oxygen determined by respiration regulates localization of Ras and prenylated proteins.
abstract: Reduction of mitochondrial DNA (mtDNA) content induces the reduction of oxidative phosphorylation and dependence on fermentative glycolysis, that is, the Warburg effect. In aggressive prostate cancer (PCa), the reduction of mtDNA reduces oxygen consumption, increases intracellular oxygen concentration, and induces constitutive activation of Ras. Many essential proteins for cell death, growth, differentiation, and development, such as Ras, require prenylation for subcellular localization and activation. Prenylation of a protein is defined as the attachment of isoprenoids to a cysteine residue at or near the C-terminus. 3-Hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGR) produces isoprenoids, and is posttranslationally regulated by oxygen. We investigated a critical role of intracellular oxygen in membrane localization of prenylated proteins. Localization of prenylated proteins (H-Ras, prelamin A/C, and Rab5a) was observed in poorly differentiated PCa (PC-3) and well-differentiated PCa (LNCaP) cells. PC-3 cells exhibited high intracellular oxygen concentration, and H-Ras, prelamin A/C, and Rab5a were localized to various membranes (Golgi and plasma membrane, nuclear membrane, and early endosomes, respectively). Remarkably, exogenous hypoxia (0.2% O2) in PC-3 cells induced intracellular hypoxia and changed the localization of the prenylated proteins. H-Ras and Rab5a were translocated to cytosol, and prelamin A/C was in the nucleus forming an abnormal nuclear envelope. The localization was reversed by mevalonate indicating the involvement of mevalonate pathway. In contrast, in LNCaP cells, exhibiting low intracellular oxygen concentration, H-Ras and Rab5a were localized in the cytosol, and prelamin A/C was inside the nucleus forming an inadequate nuclear envelope. Exogenous hyperoxia (40% O2) increased the intracellular oxygen concentration and induced Ras translocation from cytosol to the membrane. Prelamin A/C was translocated to the nuclear membrane and formed a proper nuclear envelope. Rab5a was translocated to the early endosomes. The specific localizations of the prenylated proteins were dependent on intracellular oxygen concentration. These results demonstrate that intracellular oxygen concentration regulates the localization and activation of prenylated proteins.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, 4301 West Markham, Little Rock, AR, USA.
authors.forename: A
authors.initials: A
authors.lastname: Kim
authors.affiliation: Department of Urology, University of Arkansas for Medical Sciences, 4301 West Markham, Little Rock, AR, USA.
authors.forename: R
authors.initials: R
authors.lastname: Davis
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, 4301 West Markham, Little Rock, AR, USA.
authors.forename: M
authors.initials: M
authors.lastname: Higuchi
mesh_terms: D045744:Cell Line, Tumor; D004272:DNA, Mitochondrial / Q000378:metabolism; D011992:Endosomes / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases; D008297:Male; D010085:Oxidative Phosphorylation; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000235:genetics; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D017368:Protein Prenylation / Q000235:genetics*; D020696:rab5 GTP-Binding Proteins / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D006903:Hydroxymethylglutaryl CoA Reductases; C427755:RAB5C protein, human; D020696:rab5 GTP-Binding Proteins; D010100:Oxygen