April 2009
Volume 50, Issue 13
ARVO Annual Meeting Abstract  |   April 2009
Retinoid Processing in Müller Cells
Author Affiliations & Notes
  • J. Kaylor
    Jules Stein Eye Institute, UCLA, Los Angeles, California
  • A. Miu
    Jules Stein Eye Institute, UCLA, Los Angeles, California
  • G. Travis
    Jules Stein Eye Institute, UCLA, Los Angeles, California
  • Footnotes
    Commercial Relationships  J. Kaylor, None; A. Miu, None; G. Travis, None.
  • Footnotes
    Support  NIH Grant EY11713
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 2998. doi:
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      J. Kaylor, A. Miu, G. Travis; Retinoid Processing in Müller Cells. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2998.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : The visual cycle for the regeneration of rhodopsin is well defined in RPE cells. However, several lines of evidence suggest that cones may regenerate visual pigments by a mechanism independent of the RPE that might involve Müller cells. Prior work from our laboratory indicated the existence of a retinoid isomerase (distinct from Rpe65) in chicken and ground-squirrel retinas that catalyzes the direct conversion of all-trans-retinol (all-trans-ROL) to 11-cis-retinol (11-cis-ROL). This ‘isomerase-2’ activity is coupled to a palmitoyl coenzyme A (palm CoA) dependent retinyl-ester synthase (ARAT), to yield 11-cis-retinyl palmitate (11-cis-RP) as a final product. We are working to understand the role of Müller cells in the processing of visual retinoids.

Methods: : Primary Müller cell cultures were prepared from chicken retinas. Rpe65 expression was checked by Western with a chicken Rpe65 specific antibody. We determined the levels of visual retinoids synthesized in vivo by incubation of the Müller cells with all-trans-ROL and palm CoA added to the medium. Cell homogenates were also used as an enzyme source to assay in vitro the activities of isomerase-2 and ARAT in Müller cells. Retinoids in samples were extracted with hexane and analyzed by liquid chromatography.

Results: : Cultured chicken Müller cells do not express Rpe65 based on Western analysis. Addition of all-trans-ROL and palm CoA to the culture medium resulted in the synthesis of 11-cis-ROL, all-trans-retinyl palmitate (all-trans-RP) and all-trans-retinaldehyde inside the Müller cells. Multiple 11-cis-retinyl esters were present in the media outside the cell. In the presence of palm CoA, Müller cell homogenates synthesized all-trans-RP and 11-cis-RP from all-trans-ROL substrate.

Conclusions: : Cultured chicken Müller cells contain robust ARAT activity. The Müller cells also contain isomerase-2 activity, indicated by palm CoA-dependent synthesis of 11-cis-ROL and 11-cis-RP from all-trans-ROL.

Keywords: retina • photoreceptors • retinoids/retinoid binding proteins 

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