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 #
5R01EY013434-08
Application #
7797336
Study Section
Biology and Diseases of the Posterior Eye Study Section (BDPE)
Program Officer
Mariani, Andrew P
Project Start
2001-07-01
Project End
2013-03-31
Budget Start
2010-04-01
Budget End
2011-03-31
Support Year
8
Fiscal Year
2010
Total Cost
$350,831
Indirect Cost
Name
University of Pennsylvania
Department
Physiology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Beckel, Jonathan M; Gómez, Néstor Más; Lu, Wennan et al. (2018) Stimulation of TLR3 triggers release of lysosomal ATP in astrocytes and epithelial cells that requires TRPML1 channels. Sci Rep 8:5726
Ventura, Ana Lucia Marques; Dos Santos-Rodrigues, Alexandre; Mitchell, Claire H et al. (2018) Purinergic signaling in the retina: From development to disease. Brain Res Bull :
Lu, Wennan; Gómez, Néstor M; Lim, Jason C et al. (2018) The P2Y12 Receptor Antagonist Ticagrelor Reduces Lysosomal pH and Autofluorescence in Retinal Pigmented Epithelial Cells From the ABCA4-/- Mouse Model of Retinal Degeneration. Front Pharmacol 9:242
Gómez, Néstor Más; Lu, Wennan; Lim, Jason C et al. (2018) Robust lysosomal calcium signaling through channel TRPML1 is impaired by lysosomal lipid accumulation. FASEB J 32:782-794
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Albalawi, Farraj; Lu, Wennan; Beckel, Jonathan M et al. (2017) The P2X7 Receptor Primes IL-1? and the NLRP3 Inflammasome in Astrocytes Exposed to Mechanical Strain. Front Cell Neurosci 11:227
Lu, Wennan; Albalawi, Farraj; Beckel, Jonathan M et al. (2017) The P2X7 receptor links mechanical strain to cytokine IL-6 up-regulation and release in neurons and astrocytes. J Neurochem 141:436-448
Beckel, Jonathan M; Lu, Wennan; Civan, Mortimer M et al. (2016) Treatment of Retinal Disorders with Purinergic Drugs: Beyond Receptors. J Ocul Pharmacol Ther 32:488-489
Mitchell, Claire H; Civan, Mortimer M (2016) Introduction to Purinergic Regulation in the Eye Special Issue. J Ocul Pharmacol Ther 32:485

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