title: Dysregulation of inter-photoreceptor retinoid-binding protein (IRBP) after induced Müller cell disruption.
abstract: Reduced expression of a ~150 kDa protein was unexpectedly observed while investigating Norrin protein in a transgenic murine model in which Müller cells can be selectively and inducibly disrupted. Isolation of this unknown protein via ion exchange and hydrophobic interaction chromatography followed by Tandem mass spectrometry identified it as Inter-photoreceptor retinoid-binding protein (IRBP). Significantly reduced IRBP mRNA expression was observed at the early and late stages after Müller cell disruption. IRBP protein expression was also consistently reduced to 5.7% of the control level as early as 1 week after Müller cell disruption. This down-regulation of IRBP was accompanied by focal hyperfluorescent dots and cytotoxic N-retinylidene-N-retinylethanolamine (A2E) accumulation. In vitro treatment of cone photoreceptor cell lines with conditioned medium collected from stressed Müller cells suggested that Müller cells regulated photoreceptors expression of IRBP via secreted factor(s). In vivo studies suggested that one of these secreted factors was tumour necrosis factor alpha (TNFα). These findings suggest that dysregulation of IRBP expression caused by Müller cell dysfunction may be an important early event in photoreceptor degeneration in some retinal diseases. This study reports down-regulation of inter-photoreceptor retinoid-binding protein (IRBP) in photoreceptors and retinoid cycle derangement after Müller cell disruption in a transgenic mouse model. The findings indicate that Müller cells communicate with photoreceptors in response to stress by secreting soluble protein factor(s). We propose that down-regulation of IRBP may represent an early and novel pathogenic mechanism in degenerative retinal diseases.
authors.affiliation: Save Sight Institute, the University of Sydney, Sydney, NSW, Australia.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Save Sight Institute, the University of Sydney, Sydney, NSW, Australia.
authors.forename: Weiyong
authors.initials: W
authors.lastname: Shen
authors.affiliation: Save Sight Institute, the University of Sydney, Sydney, NSW, Australia.
authors.forename: Brian
authors.initials: B
authors.lastname: Lyons
authors.affiliation: Save Sight Institute, the University of Sydney, Sydney, NSW, Australia.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Faculty of Pharmacy, the University of Sydney, Sydney, NSW, Australia.
authors.forename: Fanfan
authors.initials: F
authors.lastname: Zhou
authors.affiliation: Save Sight Institute, the University of Sydney, Sydney, NSW, Australia.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Gillies
mesh_terms: D000818:Animals; D015153:Blotting, Western; D015536:Down-Regulation; D063928:Ependymoglial Cells / Q000378:metabolism*; D005136:Eye Proteins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism*; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053719:Tandem Mass Spectrometry; D000099214:Retinol-Binding Proteins, Interstitial
chemical_list: D005136:Eye Proteins; D012177:Retinol-Binding Proteins; D000099214:Retinol-Binding Proteins, Interstitial
keywords: Müller Cell; N-retinylidene-N-retinylethanolamine; Norrin; inter-photoreceptor retinoid-binding protein; tumour necrosis factor alpha