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Homocysteine increases the expression of vascular endothelial growth factor by a mechanism involving endoplasmic reticulum stress and transcription factor ATF4
Journal article   Open access   Peer reviewed

Homocysteine increases the expression of vascular endothelial growth factor by a mechanism involving endoplasmic reticulum stress and transcription factor ATF4

C Nathaniel Roybal, Shujie Yang, Chiao-Wang Sun, Diego Hurtado, David L Vander Jagt, Tim M Townes and Steve F Abcouwer
The Journal of biological chemistry, Vol.279(15), pp.14844-14852
04/09/2004
DOI: 10.1074/jbc.M312948200
PMID: 14747470
url
https://doi.org/10.1074/jbc.M312948200View
Published (Version of record) Open Access

Abstract

Vascular endothelial growth factor (VEGF) plays a key role in the development and progression of diabetic retinopathy. We previously demonstrated that amino acid deprivation and other inducers of endoplasmic reticulum-stress (ER stress) up-regulate the expression of VEGF in the retinal-pigmented epithelial cell line ARPE-19. Because homocysteine causes ER stress, we hypothesized that VEGF expression is increased by ambient homocysteine. dl-Homocysteine-induced VEGF expression was investigated in confluent ARPE-19 cultures. Northern analysis showed that homocysteine increased steady state VEGF mRNA levels 4.4-fold. Other thiol-containing compounds, including l-homocysteine thiolactone and DTT, induced VEGF expression 7.9- and 8.8-fold. Transcriptional run-on assays and mRNA decay studies demonstrated that the increase in VEGF mRNA levels was caused by increased transcription rather than mRNA stabilization. VEGF mRNA induction paralleled that of the ER-stress gene GRP78. Homocysteine treatment caused transient phosphorylation of eIF2alpha and an increase in ATF4 protein level. Overexpression of a dominant-negative ATF4 abolished the VEGF response to homocysteine treatment and to amino acid deprivation. VEGF mRNA expression by ATF4-/- MEF did not respond to homocysteine treatment and the response was restored with expression of wild-type ATF4. These studies indicate that expression of the pro-angiogenic factor VEGF is increased by homocysteine and other thiol-containing reductive compounds via ATF4-dependent activation of VEGF transcription.
 Up-Regulation Vascular Endothelial Growth Factor A - biosynthesis Phosphorylation Nucleic Acid Synthesis Inhibitors - pharmacology Humans Neovascularization, Pathologic Stress, Physiological Activating Transcription Factor 4 Endoplasmic Reticulum - metabolism Vascular Endothelial Growth Factor A - metabolism RNA, Messenger - metabolism Dose-Response Relationship, Drug Cell Nucleus - metabolism Genes, Dominant Time Factors Transcription Factor CHOP Heat-Shock Proteins Transcription, Genetic Epithelial Cells - cytology CCAAT-Enhancer-Binding Proteins - metabolism Cell Line Promoter Regions, Genetic Molecular Chaperones Enzyme-Linked Immunosorbent Assay Reverse Transcriptase Polymerase Chain Reaction Blotting, Western Transcription Factors - metabolism Blotting, Northern Carrier Proteins - metabolism Homocysteine - physiology Protein Binding Homocysteine - chemistry Mutation DNA, Complementary - metabolism Dactinomycin - pharmacology

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