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I. Pascual, E. F. Moreira, I. R. Rodriguez; Expression and Localization of Methionine Reductase B2 in the Monkey Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5076.
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In the neural retina 70% of the methionine sulfoxide reductase (MSR) activity is due to MSRBs and 30% to MSRAs. The methionine sulfoxide reductase B2 (MSRB2), also known as CBS1, reduces the oxidized methionine-R-sulfoxide back to methionine. This process plays a critical role in recovering protein functionality and in protection against oxidative stress. MSRB2 has a typical predicted mitochondrial signal at the N-terminus, and it has been experimentally demonstrated to localize to the mitochondria. It is principally expressed in eye tissues, heart and skeletal muscle. The purpose of this study is to determine the expression and localization of MSRB2 in monkey retina and to understand its function.
Total RNA was isolated from human and monkey retinal tissues and human RPE cell lines (D407, ARPE19). cDNA was synthesized and real-time PCR was performed with SYBR Green using an ABI 7500 instrument. Immunoblot analyses were performed on the protein extracts using an anti-MSRB2 monoclonal antibody and a goat anti-mouse-HRP secondary antibody. Immunodetection of MSRB2 in the monkey retina was done using vibrotome sections. Sections (100-150µm) were incubated overnight with the anti-MSRB2 monoclonal antibody and developed with a goat anti-mouse Alexa-568 secondary antibody before imaging by confocal microscopy (Leica SP2).
MSRB2 was detected by real time PCR in neural retina, RPE/Choroid and in two RPE cell lines (D407 and ARPE19) in higher amounts than in human brain. By contrast MSRA is expressed in greater amounts in the brain than in the retina and RPE cell lines. Immunofluorescence localized MSRB2 in the outer plexiform layer in association with the synaptic mitochondria of the photoreceptors. Very little immunoreactivity was found in the photoreceptor inner segment mitochondria. MSRB2 immunostaining was also found in the ganglion cell layer and RPE.
MSRB2 is expressed in the neural retina and RPE and may be playing an important role in protection to oxidative damage especially in the synaptic mitochondria.
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