Expression and iron-dependent regulation of succinate receptor GPR91 in retinal pigment epithelium

GPR91, a succinate receptor, is expressed in retinal ganglion cells and induces vascular endothelial growth factor (VEGF) expression. RPE also expresses VEGF, but whether this cell expresses GPR91 is not known. Excessive iron is also proangiogenic, and hemochromatosis is associated with iron overloa...

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Bibliographic Details
Published in:Investigative ophthalmology & visual science 2011-05, Vol.52 (6), p.3751-3758
Main Authors: Gnana-Prakasam, Jaya P, Ananth, Sudha, Prasad, Puttur D, Zhang, Ming, Atherton, Sally S, Martin, Pamela M, Smith, Sylvia B, Ganapathy, Vadivel
Format: Article
Language:English
Subjects:
Animals
Blotting, Western
Cell Line
Female
Ferric Compounds - pharmacology
Gene Expression Regulation - physiology
Gene Silencing - physiology
Hemochromatosis - metabolism
Herpesviridae Infections - metabolism
Herpesviridae Infections - virology
Humans
Immunohistochemistry
Iron - metabolism
Male
Mice
Mice, Inbred BALB C
Mice, Inbred C57BL
Muromegalovirus - physiology
Quaternary Ammonium Compounds - pharmacology
Receptors, G-Protein-Coupled - genetics
Receptors, G-Protein-Coupled - metabolism
Retinal Pigment Epithelium - drug effects
Retinal Pigment Epithelium - metabolism
Retinitis - metabolism
Retinitis - virology
Reverse Transcriptase Polymerase Chain Reaction
RNA, Messenger - metabolism
Succinic Acid - pharmacology
Transfection
Vascular Endothelial Growth Factor A - genetics
Vascular Endothelial Growth Factor A - metabolism
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Summary:GPR91, a succinate receptor, is expressed in retinal ganglion cells and induces vascular endothelial growth factor (VEGF) expression. RPE also expresses VEGF, but whether this cell expresses GPR91 is not known. Excessive iron is also proangiogenic, and hemochromatosis is associated with iron overload. Therefore, we examined the expression and iron-dependent regulation of GPR91 in the RPE. GPR91 expression was examined by RT-PCR and immunohistochemistry. Hemochromatosis mice, cytomegalovirus (CMV) infection of retina, expression of CMV-US2 in RPE, and exposure of RPE to ferric ammonium citrate (FAC) were used to examine the iron-dependent regulation of GPR91 expression. VEGF expression was quantified by qPCR. Knockdown of GPR91 in ARPE-19 cells was achieved with shRNA. GPR91 was expressed in RPE but only in the apical membrane. Retinal expression of GPR91 was higher in hemochromatosis (Hfe(-/-)) mice than in wild-type (WT) mice. Primary RPE cells from Hfe(-/-) mice had increased GPR91 expression compared with WT RPE cells. Iron accumulation in cells induced by CMV infection, expression of CMV-US2, or treatment with FAC increased GPR91 expression. VEGF expression in the Hfe(-/-) mouse retina was increased at ages younger than 18 months, but the expression was downregulated at older ages. The involvement of GPR91 in succinate-induced expression of VEGF in RPE cells was confirmed with GPR91-specific shRNA. GPR91 is expressed in the RPE with specific localization to the apical membrane, indicating that succinate in the subretinal space serves as the GPR91 agonist. Excessive iron in the retina and RPE enhances GPR91 expression; however, VEGF expression does not always parallel GPR91 expression.
ISSN:1552-5783
0146-0404
1552-5783
DOI:10.1167/iovs.10-6722