187. TFEB-Mediated Clearance of the Lipofuscin Fluorophore A2E

Abstract

Abnormal accumulation of various by-products of the visual cycle, including the diretinoid-pyridinium-ethanolamine (A2E), in retinal pigment epithelium (RPE) is an hallmark of both Stargardt disease (STGD) and age-related macular degeneration (AMD). This is responsible for RPE and, consequently, photoreceptor (PR) cell death. A2E storage in RPE lysosomes has been shown to reduce both the capacity of RPE to degrade phagocytized PR outer segments and autophagosome biogenesis, trafficking and autophagic flux. The transcription factor EB (TFEB) is a master regulator of cellular clearance. Here we tested if TFEB overexpression induces A2E clearance from the RPE cells. We have generated a plasmid encoding for a double-serine mutant (S142A, S211A) form of TFEB, which is constitutively active. We have transfected this plasmid in the human RPE-derived ARPE19 cells to evaluate TFEB activation of its transcriptional targets and ability to clear A2E after loading. We found that TFEB overexpression in ARPE19 cells results in the induction of TFEB transcriptional targets involved in cellular clearance. Importantly, TFEB overexpression in ARPE19 cells was associated with reduction of intracellular A2E accumulation. Taken together these results suggest that TFEB overexpression is an effective strategy to promote A2E clearance in vitro. Further studies will clarify if this holds true in vivo. These results may have implications for the therapy of both STGD and the more common AMD.