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Published on: May 6, 2015
The photoreceptor protective cGMP-analog Rp-8-Br-PET-cGMPS interacts with cGMP-interactors PKGI, PDE1, PDE6, and PKAI
Michel Rasmussen1, Arianna Tolone2, Francois Paquet-Durand2
1Faculty of Medicine, Department of Clinical Sciences Lund, Lund University, Ophthalmology, Lund, Sweden.
Abstract:
The inherited eye disease retinitis pigmentosa (RP) causes the loss of photoreceptors by a still unknown cell death mechanism. During this degeneration, cyclic guanosine-3',5'-monophosphate (cGMP) levels become elevated, leading to over-activation of the cGMP-binding protein cGMP-dependent protein kinase (PKG). cGMP analogs selectively modified to have inhibitory actions on PKG have aided in impeding photoreceptor death, and one such cGMP analog is Rp-8-Br-PET-cGMPS. However, cGMP analogs have previously been shown to interact with numerous targets, so to better understand the therapeutic action of Rp-8-Br-PET-cGMPS, it is necessary to elucidate its target-selectivity and hence what potential cellular mechanism(s) it may affect within the photoreceptors. Here, we, therefore, applied affinity chromatography together with mass spectrometry to isolate and identify Rp-8-Br-PET-cGMPS interactors from retinas derived from three different murine RP models (i.e., rd1, rd2, and rd10 mice). Our findings revealed that Rp-8-Br-PET-cGMPS bound seven known cGMP-binding proteins, including PKG1β, PDE1β, PDE1c, PDE6α, and PKA1α. Furthermore, an additional 28 proteins were found to be associated with Rp-8-Br-PET-cGMPS. This latter group included MAPK1/3, which is known to connect with cGMP/PKG in other systems. However, in organotypic retinal cultures, Rp-8-Br-PET-cGMPS had no effect on photoreceptor MAPK1/3 expression or activity. To summarize, Rp-8-Br-PET-cGMPS is more target specific compared to regular cGMP.
Insights
This study investigated the drug Rp-8-Br-PET-cGMPS for retinitis pigmentosa (RP). Researchers found it binds specifically to certain proteins, suggesting a targeted therapeutic action for photoreceptor protection in RP.
Area of Science:
- Ophthalmology
- Neuroscience
- Molecular Biology
Background:
- Retinitis pigmentosa (RP) is an inherited eye disease causing photoreceptor degeneration via an unknown mechanism.
- Elevated cyclic guanosine-3',5'-monophosphate (cGMP) levels during RP lead to over-activation of cGMP-dependent protein kinase (PKG).
- cGMP analogs, like Rp-8-Br-PET-cGMPS, show therapeutic potential by inhibiting PKG but require target-selectivity assessment.
Purpose of the Study:
- To identify the specific protein targets of the cGMP analog Rp-8-Br-PET-cGMPS in the retina.
- To understand the potential therapeutic mechanisms of Rp-8-Br-PET-cGMPS in photoreceptor degeneration.
- To assess the target-selectivity of Rp-8-Br-PET-cGMPS compared to standard cGMP.
Main Methods:
- Affinity chromatography coupled with mass spectrometry was employed.
- Rp-8-Br-PET-cGMPS interactors were isolated from retinas of three murine RP models (rd1, rd2, rd10).
- Protein binding and activity were analyzed in organotypic retinal cultures.
Main Results:
- Rp-8-Br-PET-cGMPS bound to seven known cGMP-binding proteins, including PKG1β, PDE1β, PDE1c, PDE6α, and PKA1α.
- An additional 28 proteins, including MAPK1/3, were identified as Rp-8-Br-PET-cGMPS interactors.
- Rp-8-Br-PET-cGMPS did not affect photoreceptor MAPK1/3 expression or activity in retinal cultures.
Conclusions:
- Rp-8-Br-PET-cGMPS exhibits greater target specificity than regular cGMP.
- The findings support Rp-8-Br-PET-cGMPS as a potentially more refined therapeutic agent for RP.
- Understanding Rp-8-Br-PET-cGMPS target interactions is crucial for elucidating its therapeutic effects on photoreceptor survival.
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