Increased retinal expression of the pro-angiogenic receptor GPR91 via BMP6 in a mouse model of juvenile hemochromatosis

Pachiappan Arjunan, Jaya Pranava Gnana-Prakasam, Sudha Ananth, Michelle A. Romej, Veeranan Karmegam Rajalakshmi, Puttur D Prasad, Pamela Moore Martin, Mariappan Gurusamy, Muthusamy Thangaraju, Yangzom D. Bhutia, Vadivel Ganapathy

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

PURPOSE. Hemochromatosis, an iron-overload disease, occurs as adult and juvenile types. Mutations in hemojuvelin (HJV), an iron-regulatory protein and a bone orphogenetic protein (BMP) coreceptor, underlie most of the juvenile type. Hjv-/-mice accumulate excess iron in retina and exhibit aberrant vascularization and angiomas. A succinate receptor, GPR91, is pro-angiogenic in retina. We hypothesized that Hjv-/- retinas have increased BMP signaling and increased GPR91 expression as the basis of angiomas. METHODS. Expression of GPR91 was examined by qPCR, immunofluorescence, and Western blot in wild-type and Hjv-/- mouse retinas and pRPE cells. Influence of excess iron and BMP6 on GPR91 expression was investigated in ARPE-19 cells, and wild-type and Hjv-/- pRPE cells. Succinate was used to activate GPR91 and determine the effects of GPR91 signaling on VEGF expression. Signaling of BMP6 was studied by the expression of Smad1/5/8 and pSmad4, and the BMP-target gene Id1. The interaction of pSmad4 with GPR91 promoter was studied by ChIP. RESULTS. Expression of GPR91 was higher in Hjv-/- retinas and RPE than in wild-type counterparts. Unexpectedly, BMP signaling was increased, not decreased, in Hjv-/- retinas and RPE. Bone morphogenetic protein 6 induced GPR91 in RPE, suggesting that increased BMP signaling in Hjv-/- retinas was likely responsible for GPR91 upregulation. Exposure of RPE to excess iron and succinate as well as BMP6 and succinate increased VEGF expression. Bone morphogenetic protein 6 promoted the interaction of pSmad4 with GPR91 promoter in RPE. CONCLUSIONS. G-protein-coupled receptor 91 is a BMP6 target and Hjv deletion enhances BMP signaling in retina, thus underscoring a role for excess iron and hemochromatosis in abnormal retinal vascularization.

Original languageEnglish (US)
Pages (from-to)1612-1619
Number of pages8
JournalInvestigative Ophthalmology and Visual Science
Volume57
Issue number4
DOIs
StatePublished - Apr 1 2016

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Retina
Succinic Acid
Bone Morphogenetic Protein 6
Iron
Hemochromatosis
Hemangioma
Vascular Endothelial Growth Factor A
Iron-Regulatory Proteins
Iron Overload
Type 2 Hemochromatosis
G-Protein-Coupled Receptors
Fluorescent Antibody Technique
Up-Regulation
Western Blotting
Bone and Bones
Mutation
Genes
Proteins

Keywords

  • Age-related macular degeneration
  • BMP6 signaling
  • Juvenile hemochromatosis
  • Retinal pigment epithelium
  • Succinate receptor-GPR91

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

Cite this

Increased retinal expression of the pro-angiogenic receptor GPR91 via BMP6 in a mouse model of juvenile hemochromatosis. / Arjunan, Pachiappan; Gnana-Prakasam, Jaya Pranava; Ananth, Sudha; Romej, Michelle A.; Rajalakshmi, Veeranan Karmegam; Prasad, Puttur D; Martin, Pamela Moore; Gurusamy, Mariappan; Thangaraju, Muthusamy; Bhutia, Yangzom D.; Ganapathy, Vadivel.

In: Investigative Ophthalmology and Visual Science, Vol. 57, No. 4, 01.04.2016, p. 1612-1619.

Research output: Contribution to journalArticle

Arjunan, Pachiappan ; Gnana-Prakasam, Jaya Pranava ; Ananth, Sudha ; Romej, Michelle A. ; Rajalakshmi, Veeranan Karmegam ; Prasad, Puttur D ; Martin, Pamela Moore ; Gurusamy, Mariappan ; Thangaraju, Muthusamy ; Bhutia, Yangzom D. ; Ganapathy, Vadivel. / Increased retinal expression of the pro-angiogenic receptor GPR91 via BMP6 in a mouse model of juvenile hemochromatosis. In: Investigative Ophthalmology and Visual Science. 2016 ; Vol. 57, No. 4. pp. 1612-1619.
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abstract = "PURPOSE. Hemochromatosis, an iron-overload disease, occurs as adult and juvenile types. Mutations in hemojuvelin (HJV), an iron-regulatory protein and a bone orphogenetic protein (BMP) coreceptor, underlie most of the juvenile type. Hjv-/-mice accumulate excess iron in retina and exhibit aberrant vascularization and angiomas. A succinate receptor, GPR91, is pro-angiogenic in retina. We hypothesized that Hjv-/- retinas have increased BMP signaling and increased GPR91 expression as the basis of angiomas. METHODS. Expression of GPR91 was examined by qPCR, immunofluorescence, and Western blot in wild-type and Hjv-/- mouse retinas and pRPE cells. Influence of excess iron and BMP6 on GPR91 expression was investigated in ARPE-19 cells, and wild-type and Hjv-/- pRPE cells. Succinate was used to activate GPR91 and determine the effects of GPR91 signaling on VEGF expression. Signaling of BMP6 was studied by the expression of Smad1/5/8 and pSmad4, and the BMP-target gene Id1. The interaction of pSmad4 with GPR91 promoter was studied by ChIP. RESULTS. Expression of GPR91 was higher in Hjv-/- retinas and RPE than in wild-type counterparts. Unexpectedly, BMP signaling was increased, not decreased, in Hjv-/- retinas and RPE. Bone morphogenetic protein 6 induced GPR91 in RPE, suggesting that increased BMP signaling in Hjv-/- retinas was likely responsible for GPR91 upregulation. Exposure of RPE to excess iron and succinate as well as BMP6 and succinate increased VEGF expression. Bone morphogenetic protein 6 promoted the interaction of pSmad4 with GPR91 promoter in RPE. CONCLUSIONS. G-protein-coupled receptor 91 is a BMP6 target and Hjv deletion enhances BMP signaling in retina, thus underscoring a role for excess iron and hemochromatosis in abnormal retinal vascularization.",
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T1 - Increased retinal expression of the pro-angiogenic receptor GPR91 via BMP6 in a mouse model of juvenile hemochromatosis

AU - Arjunan, Pachiappan

AU - Gnana-Prakasam, Jaya Pranava

AU - Ananth, Sudha

AU - Romej, Michelle A.

AU - Rajalakshmi, Veeranan Karmegam

AU - Prasad, Puttur D

AU - Martin, Pamela Moore

AU - Gurusamy, Mariappan

AU - Thangaraju, Muthusamy

AU - Bhutia, Yangzom D.

AU - Ganapathy, Vadivel

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N2 - PURPOSE. Hemochromatosis, an iron-overload disease, occurs as adult and juvenile types. Mutations in hemojuvelin (HJV), an iron-regulatory protein and a bone orphogenetic protein (BMP) coreceptor, underlie most of the juvenile type. Hjv-/-mice accumulate excess iron in retina and exhibit aberrant vascularization and angiomas. A succinate receptor, GPR91, is pro-angiogenic in retina. We hypothesized that Hjv-/- retinas have increased BMP signaling and increased GPR91 expression as the basis of angiomas. METHODS. Expression of GPR91 was examined by qPCR, immunofluorescence, and Western blot in wild-type and Hjv-/- mouse retinas and pRPE cells. Influence of excess iron and BMP6 on GPR91 expression was investigated in ARPE-19 cells, and wild-type and Hjv-/- pRPE cells. Succinate was used to activate GPR91 and determine the effects of GPR91 signaling on VEGF expression. Signaling of BMP6 was studied by the expression of Smad1/5/8 and pSmad4, and the BMP-target gene Id1. The interaction of pSmad4 with GPR91 promoter was studied by ChIP. RESULTS. Expression of GPR91 was higher in Hjv-/- retinas and RPE than in wild-type counterparts. Unexpectedly, BMP signaling was increased, not decreased, in Hjv-/- retinas and RPE. Bone morphogenetic protein 6 induced GPR91 in RPE, suggesting that increased BMP signaling in Hjv-/- retinas was likely responsible for GPR91 upregulation. Exposure of RPE to excess iron and succinate as well as BMP6 and succinate increased VEGF expression. Bone morphogenetic protein 6 promoted the interaction of pSmad4 with GPR91 promoter in RPE. CONCLUSIONS. G-protein-coupled receptor 91 is a BMP6 target and Hjv deletion enhances BMP signaling in retina, thus underscoring a role for excess iron and hemochromatosis in abnormal retinal vascularization.

AB - PURPOSE. Hemochromatosis, an iron-overload disease, occurs as adult and juvenile types. Mutations in hemojuvelin (HJV), an iron-regulatory protein and a bone orphogenetic protein (BMP) coreceptor, underlie most of the juvenile type. Hjv-/-mice accumulate excess iron in retina and exhibit aberrant vascularization and angiomas. A succinate receptor, GPR91, is pro-angiogenic in retina. We hypothesized that Hjv-/- retinas have increased BMP signaling and increased GPR91 expression as the basis of angiomas. METHODS. Expression of GPR91 was examined by qPCR, immunofluorescence, and Western blot in wild-type and Hjv-/- mouse retinas and pRPE cells. Influence of excess iron and BMP6 on GPR91 expression was investigated in ARPE-19 cells, and wild-type and Hjv-/- pRPE cells. Succinate was used to activate GPR91 and determine the effects of GPR91 signaling on VEGF expression. Signaling of BMP6 was studied by the expression of Smad1/5/8 and pSmad4, and the BMP-target gene Id1. The interaction of pSmad4 with GPR91 promoter was studied by ChIP. RESULTS. Expression of GPR91 was higher in Hjv-/- retinas and RPE than in wild-type counterparts. Unexpectedly, BMP signaling was increased, not decreased, in Hjv-/- retinas and RPE. Bone morphogenetic protein 6 induced GPR91 in RPE, suggesting that increased BMP signaling in Hjv-/- retinas was likely responsible for GPR91 upregulation. Exposure of RPE to excess iron and succinate as well as BMP6 and succinate increased VEGF expression. Bone morphogenetic protein 6 promoted the interaction of pSmad4 with GPR91 promoter in RPE. CONCLUSIONS. G-protein-coupled receptor 91 is a BMP6 target and Hjv deletion enhances BMP signaling in retina, thus underscoring a role for excess iron and hemochromatosis in abnormal retinal vascularization.

KW - Age-related macular degeneration

KW - BMP6 signaling

KW - Juvenile hemochromatosis

KW - Retinal pigment epithelium

KW - Succinate receptor-GPR91

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