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Y. Chen, S. Sun, X. Liu; The Role of AIPL1 in the Synthesis of Rod cGMP Phosphodiesterase. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1679.
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© ARVO (1962-2015); The Authors (2016-present)
Leber congenital amaurosis (LCA) is a common cause of infantile blindness. Here we study one LCA subtype caused by a mutation in the gene encoding the aryl hydrocarbon receptor-interacting protein like 1 (AIPL1). AIPL1 is an FK506-binding homolog specifically expressed in photoreceptor cells. Previous studies suggest that AIPL1 serves as a specialized chaperone for the synthesis of rod cGMP phosphodiesterase (PDE6) in photoreceptor cells. However, it is not yet clear whether AIPL1 primarily serves as a quantity control or a quality control. To address this question, we co-express AIPL1 and subunits of PDE6 followed by biochemical characterization.
To introduce AIPL1 into HEK293 cells, an AIPL1 HEK 293 stable cell line was established. Plasmids expressing PDE6 subunits were then transduced into HEK293 cells and the AIPL1 HEK293 stable cell line, respectively. Immunoblotting was used to determine the expression levels for PDE6 subunits. SDS-PAGE followed by immunoblotting was used to evaluate the prenylation of PDE6 catalytic subunits.
An AIPL1 HEK293 stable cell line was created with a significantly higher AIPL1 expression level, compared to transient expression. However, the expression levels for any transfected individual PDE6 subunits did not increase in the presence of AIPL1. Electrophoretic mobility on SDS-PAGE showed that prenylation of PDE6 subunits was not affected.
Co-expression of AIPL1 with individual PDE6 subunits in non-photoreceptor cells does not increase the amount of PDE6, suggesting that AIPL1 is required but not sufficient for PDE6 synthesis. Determination of PDE6 enzymatic activity in combination with prenylation enhancement treatment will help address how AIPL1 serves as a quality control for PDE6 synthesis.
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