# Mechanisms that regulate RPE65 isomerase in normal and blindness-associated RPE

> **NIH NIH R01** · LSU HEALTH SCIENCES CENTER · 2020 · $367,500

## Abstract

Project Summary/Abstract
Continuous regeneration of the 11-cis-retinal (11cRAL) chromophore of rhodopsin and cone visual pigments is
essential for sustaining light-sensitivity and survival of photoreceptors. RPE65 is a key retinoid isomerase in
the visual cycle responsible for regenerating 11cRAL. The importance of the RPE65 function in vision and
retinal health is reflected by the facts that over 100 different mutations in the RPE65 gene are associated with
Leber congenital amaurosis (LCA) and retinitis pigmentosa (RP). The long-term goals of the proposed
research are 1) to decipher the mechanisms that regulate the expression, stability and activity of normal and
disease-causing mutant RPE65s, 2) to identify the molecular pathway leading to photoreceptor death in
patients with RPE65 mutations and 3) to develop a new therapeutic intervention to prevent or delay vision loss
in the patients. In the recent and preliminary studies, we found that fatty acid transport protein 4 (FATP4),
elongation of very long chain fatty acids 1 (ELOVL1) and 26S proteasome non-ATPase regulatory subunit 13
(PSMD13) are negative regulators of RPE65. FATP4 and ELOVL1 inhibited synthesis of 11-cis-retinol
catalyzed by RPE65 while PSMD13 promoted degradation of misfolded RPE65 via the ubiquitination-
dependent proteasomal pathway in the retinal pigment epithelium (RPE). We observed that the majority of
pathogenic missense mutations are mapped on the non-active sites of RPE65 and many of these mutants
underwent the PSMD13-mediated proteasomal degradation due to misfolding. Using a living cell-based assay,
we discovered that chemical chaperones such as 4-phenylbutyrate (PBA) and glycerol can rescue the stability,
membrane-association and the isomerase function of many pathogenic RPE65s with non-active site mutations.
Importantly, PBA (a FDA-approved medication) improved cone survival and function in a mouse model of LCA
caused by R91W RPE65, the most frequent LCA-associated RPE65 mutant. In addition, our preliminary
studies showed that deletion of FATP4 in the R91W knock-in (KI) mouse dramatically improved cone survival
and function. To capitalize on these findings, we propose to accomplish two specific aims in the proposed
project. Specific Aim 1 is to identify the molecular mechanisms of how FATP4-deficiency improves cone
survival and vision in the KI mouse model of LCA. To this end, we will analyze the visual cycle and the
pathogenic pathways leading to cone death in the KI mouse. We will also test if FATP4 suppressor and PBA
can exert synergistic effects on long-term preservation of cone vision in the KI mouse. Specific Aim 2 is to test
the hypothesis that RPE-specific knockout of ELOVL1 increases synthesis of the visual chromophores in
mouse with wild-type or the mutant RPE65, thereby improving cone survival and function in the KI mouse. We
will also analyze the molecular mechanisms by which ELOVL1 inhibits synthesis of 11-cis-retinol catalyzed by
RPE65. The results of ...

## Key facts

- **NIH application ID:** 10000925
- **Project number:** 5R01EY028572-03
- **Recipient organization:** LSU HEALTH SCIENCES CENTER
- **Principal Investigator:** Minghao Jin
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $367,500
- **Award type:** 5
- **Project period:** 2018-09-30 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10000925

## Citation

> US National Institutes of Health, RePORTER application 10000925, Mechanisms that regulate RPE65 isomerase in normal and blindness-associated RPE (5R01EY028572-03). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10000925. Licensed CC0.

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