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Saravanan Kolandaivelu, Joseph Murphy; PRCD, A Protein Linked to Retinitis Pigmentosa is Palmitoylated. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4647.
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© ARVO (1962-2015); The Authors (2016-present)
The lipid modifications of proteins play important roles in their assembly and targeting to specific cellular compartments and in the anchoring of proteins to membranes. Among the common lipid modifications, protein palmitoylation is unique in that this modification is reversible, which thus enables its dynamic regulation within the cell. In addition, palmitoylation leads to the modification of a specific cysteine residue of a protein. To get insights into the role of palmitoylation in retinal photoreceptors, we identified palmitoylated proteins in isolated mouse retinas. Here, we report that progressive rod-cone degeneration (PRCD), a photoreceptor protein, is palmitoylated. The purpose of this study is to decipher the need for palmitoylation in PRCD function.
To isolate palmitoylated proteins, we used acyl resin-assisted capture (acyl-RAC). Isolated proteins were identified by mass spectrometry. PRCD was identified as one of the palmitoylated proteins in our screen. Lipid modification of PRCD was further confirmed by labeling with chemical analog “17-ODYA”, followed by click chemistry. In addition, we investigated the importance of the PRCD palmitoylation in both retina explants and in a cell culture system, using chemical analog 17-ODYA.
Several palmitoylated proteins were identified in the retina using the acyl-RAC method. They included Go alpha and rhodopsin, known to be palmitoylated, which thus confirmed the validity of our screening strategy. Importantly, PRCD was identified as one of our hits. The palmitoylation of PRCD was further confirmed in ex-vivo retinal culture. Furthermore, our results showed that disrupting PRCD palmitoylation, either chemically or by genetically eliminating the modified cysteine, dramatically affected the stability and subcellular localization of this protein.
Our results demonstrate that PRCD is modified by a palmitoyl lipid moiety, which is crucial for its stability and proper localization and function of photoreceptor cells. Here, we demonstrated that palmytoylation of a single cysteine is crucial for the stability and proper targeting of PRCD in retinal photoreceptors. Mutation of the same cysteine has been linked to the development of retinitis pigmentosa in humans.
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