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Raju V S Rajala, Yuhong Wang, Michelle Ranjo-Bishop, Ammaji Rajala; Characterization of Src-homology phosphotyrosyl phosphatase 2 in the Retina. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1757.
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© 2017 Association for Research in Vision and Ophthalmology.
Reactive oxygen species (ROS) play a multitude of signaling roles in different organisms from bacteria to mammalian cells. They were initially thought to be toxic byproducts of aerobic metabolism, but have now been acknowledged as central players in the complex signaling network of cells. Mild concentrations of ROS have been shown to inhibit the activity of protein tyrosine phosphatase, PTP1B through oxidative inactivation of catalytic cysteine, which is in the active site of PTP1B. Studies from our laboratory show that pharmacological inhibition or genetic deletion of PTP1B in photoreceptors resulted in the activation of a neuroprotective insulin receptor survival signaling in both rods and cones. Our laboratory is working towards identification of endogenous proteins that can stimulate ROS production to inhibit PTP1B activity. Src-homology phosphotyrosyl phosphatase 2 (Shp2) has recently been shown to stimulate ROS production in macrophages. In this study, we characterized Shp2 in the retina and studied the effect of Shp2 on ROS generation in cultured R28 retinal neurons.
Immunohistochemistry was used to characterize Shp2 expression in the retina, using cryo-, paraffin-, prefer-, and methanol-fixed tissues from bovine, wild-type mouse, and cone-dominant Nrl-/- mouse retinas. Mouse retinas were isolated from dark- and light-adapted (300 lux) conditions. Retinas were subjected to immunoblot analysis to study the state of phosphorylation on Shp2 as a function of its activation. Shp2 activity was also measured. Cultured R28 retinal neurons were transfected with Shp2 wild-type and inactive mutant constructs, and the production of ROS was examined.
Our results show that Shp2 is expressed in both rod and cone photoreceptor cells, in addition to the inner retinal layers. We also found significantly higher levels of tyrosine phosphorylation and Shp2 phosphatase activity in light-adapted retinas than in dark-adapted retinas. We found that catalytically inactive Shp2 (cysteine to serine substitution) fails to generate ROS, whereas wild-type Shp2 promotes ROS production in R28 retinal neurons.
Our data show the expression of Shp2 in various layers of the retina. Our neuronal cell culture data show that Shp2 promotes ROS production in vitro.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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