@article {707, title = {Silencing of tuberin enhances photoreceptor survival and function in a preclinical model of retinitis pigmentosa (an american ophthalmological society thesis).}, journal = {Trans Am Ophthalmol Soc}, volume = {112}, year = {2014}, month = {2014 Jul}, pages = {103-15}, abstract = {

PURPOSE: To assess the functional consequences of silencing of tuberin, an inhibitor of the mTOR signaling pathway, in a preclinical model of retinitis pigmentosa (RP) in order to test the hypothesis that insufficient induction of the protein kinase B (PKB)-regulated tuberin/mTOR self-survival pathway initiates apoptosis.

METHODS: In an unbiased genome-scale approach, kinase peptide substrate arrays were used to analyze self-survival pathways at the onset of photoreceptor degeneration. The mutant Pde6b(H620Q)/Pde6b(H620Q) at P14 and P18 photoreceptor outer segment (OS) lysates were labeled with P-ATP and hybridized to an array of 1,164 different synthetic peptide substrates. At this stage, OS of Pde6b(H620Q)/Pde6b(H620Q) rods are morphologically normal. In vitro kinase assays and immunohistochemistry were used to validate phosphorylation. Short hairpin RNA (shRNA) gene silencing was used to validate tuberin{\textquoteright}s role in regulating survival.

RESULTS: At the onset of degeneration, 162 peptides were differentially phosphorylated. Protein kinases A, G, C (AGC kinases), and B exhibited increased activity in both peptide array and in vitro kinase assays. Immunohistochemical data confirmed altered phosphorylation patterns for phosphoinositide-dependent kinase-1 (PDK1), ribosomal protein S6 (RPS6), and tuberin. Tuberin gene silencing rescued photoreceptors from degeneration.

CONCLUSIONS: Phosphorylation of tuberin and RPS6 is due to the upregulated activity of PKB. PKB/tuberin cell growth/survival signaling is activated before the onset of degeneration. Substrates of the AGC kinases in the PKB/tuberin pathway are phosphorylated to promote cell survival. Knockdown of tuberin, the inhibitor of the mTOR pathway, increased photoreceptor survival and function in a preclinical model of RP.

}, keywords = {Animals, Apoptosis, Disease Models, Animal, Gene Silencing, Mice, Mice, Mutant Strains, Phosphorylation, Phosphotransferases, Proto-Oncogene Proteins c-akt, Retinitis Pigmentosa, Ribosomal Protein S6, Signal Transduction, Tumor Suppressor Proteins}, issn = {1545-6110}, author = {Tsang, Stephen H and Chan, Lawrence and Tsai, Yi-Ting and Wu, Wen-Hsuan and Hsu, Chun-Wei and Yang, Jin and Tosi, Joaquin and Wert, Katherine J and Davis, Richard J and Mahajan, Vinit B} }