Ero1-L alpha plays a key role in a HIF-1-mediated pathway to improve disulfide bond formation and VEGF secretion under hypoxia: implication for cancer.
Oxygen is the ultimate source of oxidizing power for disulfide bond formation, suggesting that under limiting oxygen proper protein folding might be compromised. We show that secretion of vascular endothelial growth factor (VEGF), a protein with multiple disulfide bonds, was indeed impeded under hypoxia and was partially restored by artificial increase of oxidizing equivalents with diamide. Physiologically, the oxireductase endoplasmic reticulum oxidoreductin-1 (Ero1)-L alpha, but not other proteins in the relay of disulfide formation, was strongly upregulated by hypoxia and independently by hypoglycemia, two known accompaniments of tumors. Further, we provide genetic evidence that induction of Ero1-L alpha by hypoxia and hypoglycemia is mediated by the transcription factor hypoxia-inducible factor 1 (HIF-1) but is independent of p53. In natural human tumors, Ero1-L alpha mRNA was specifically induced in hypoxic microenvironments coinciding with that of upregulated VEGF expression. To establish a physiological relevance to modulations in Ero1-L alpha levels, we showed that even a modest, two- to three-fold reduction in Ero1-L alpha production via siRNA leads to significant inhibition of VEGF secretion, a compromised proliferation capacity and enhanced apoptosis. Together, these findings demonstrate that hypoxic induction of Ero1-L alpha is the key adaptive response in a previously unrecognized HIF-1-mediated pathway that operates to improve protein secretion under hypoxia and might be harnessed for inhibiting tumor growth via inhibiting VEGF-driven angiogenesis.
May
Dalit
D
Department of Molecular Biology, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
Itin
Ahuva
A
Gal
Oded
O
Kalinski
Hagar
H
Feinstein
Elena
E
Keshet
Eli
E
D000818:Animals; D017209:Apoptosis; D001932:Brain Neoplasms / Q000473:pathology; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D015687:Cell Hypoxia; D049109:Cell Proliferation; D004268:DNA-Binding Proteins / Q000494:pharmacology*; D005910:Glioma / Q000473:pathology; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D007003:Hypoglycemia; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008113:Liver Neoplasms / Q000473:pathology; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology*; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic; D009687:Nuclear Proteins / Q000494:pharmacology*; D010088:Oxidoreductases / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology*; D014157:Transcription Factors / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; C405327:ERO1A protein, human; D010088:Oxidoreductases