Lysosomal enzymes require an acidic pH to degrade engulfed material. We show here that the lysosomal pH of RPE cells from ABCA4-/- mice is elevated as compared to age matched controls. As the ABCA4 gene is mutated in Stargardt's disease, and as accumulation of partially degraded material in and around RPE cells is a key characteristic of the disease, we hypothesize that restoring an acid pH to the lysosomes will be beneficial. High-throughput screening indicates that lysosomes of perturbed RPE cells in culture are acidified by cytoplasmic cAMP, and by agonists which stimulate receptors coupled to the Gas protein. Elevation of cAMP increases the clearance of outer segments by RPE cells, demonstrating an improvement in function. This proposal investigates the contribution of cAMP, the Cl- channel CFTR, and the vesicular proton pump vH+ATPase to the restoration of lysosomal acidity. It will determine the relationship between age, A2E and lysosomal pH in RPE cells from ABCA4-/- mice and confirm that cAMP restores lysosomal acidity the these RPE cells using both in vitro and in vivo treatment strategies.

Public Health Relevance

Stargardt's disease is an early-onset form of macular degeneration characterized by the accumulation of partially degraded material in and around RPE cells. This proposal will explore a newly identified defect in the lysosomal pH of RPE cells from the ABCA4-/- mouse model of Stargardt's disease that may slow processing of photoreceptor outer segments, develop treatments to restore this defect, and determine how these treatments work.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY013434-10
Application #
8247083
Study Section
Biology and Diseases of the Posterior Eye Study Section (BDPE)
Program Officer
Neuhold, Lisa
Project Start
2001-07-01
Project End
2014-03-31
Budget Start
2012-04-01
Budget End
2014-03-31
Support Year
10
Fiscal Year
2012
Total Cost
$336,798
Indirect Cost
$122,958
Name
University of Pennsylvania
Department
Physiology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Xia, Jingsheng; Lim, Jason C; Lu, Wennan et al. (2012) Neurons respond directly to mechanical deformation with pannexin-mediated ATP release and autostimulation of P2X7 receptors. J Physiol 590:2285-304
Zhang, Mei; Hu, Huiling; Zhang, Xiulan et al. (2010) The A3 adenosine receptor attenuates the calcium rise triggered by NMDA receptors in retinal ganglion cells. Neurochem Int 56:35-41
Hu, Huiling; Lu, Wennan; Zhang, Mei et al. (2010) Stimulation of the P2X7 receptor kills rat retinal ganglion cells in vivo. Exp Eye Res 91:425-32

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