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.

National Institute of Health (NIH)
National Eye Institute (NEI)
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Biology and Diseases of the Posterior Eye Study Section (BDPE)
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Neuhold, Lisa
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University of Pennsylvania
Schools of Medicine
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Mitchell, Claire H; Stamer, W Daniel (2016) Dedication of Special Issue on Purinergic Regulation in the Eye to Mortimer M. Civan. J Ocul Pharmacol Ther 32:484
Mitchell, Claire H; Civan, Mortimer M (2016) Introduction to Purinergic Regulation in the Eye Special Issue. J Ocul Pharmacol Ther 32:485
Lim, Jason C; Lu, Wennan; Beckel, Jonathan M et al. (2016) Neuronal Release of Cytokine IL-3 Triggered by Mechanosensitive Autostimulation of the P2X7 Receptor Is Neuroprotective. Front Cell Neurosci 10:270
(2016) Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12:1-222
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
Lu, Wennan; Hu, HuiLing; Sévigny, Jean et al. (2015) Rat, mouse, and primate models of chronic glaucoma show sustained elevation of extracellular ATP and altered purinergic signaling in the posterior eye. Invest Ophthalmol Vis Sci 56:3075-83
Beckel, Jonathan M; Daugherty, Stephanie L; Tyagi, Pradeep et al. (2015) Pannexin 1 channels mediate the release of ATP into the lumen of the rat urinary bladder. J Physiol 593:1857-71
Frost, Laura S; Mitchell, Claire H; Boesze-Battaglia, Kathleen (2014) Autophagy in the eye: implications for ocular cell health. Exp Eye Res 124:56-66
Coffey, E E; Beckel, J M; Laties, A M et al. (2014) Lysosomal alkalization and dysfunction in human fibroblasts with the Alzheimer's disease-linked presenilin 1 A246E mutation can be reversed with cAMP. Neuroscience 263:111-24
Sanderson, Julie; Dartt, Darlene A; Trinkaus-Randall, Vickery et al. (2014) Purines in the eye: recent evidence for the physiological and pathological role of purines in the RPE, retinal neurons, astrocytes, Müller cells, lens, trabecular meshwork, cornea and lacrimal gland. Exp Eye Res 127:270-9

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