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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 J+Neurosci
2016 ; 36
(21
): 5808-19
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Pharmacological Amelioration of Cone Survival and Vision in a Mouse Model for
Leber Congenital Amaurosis
#MMPMID27225770
Li S
; Samardzija M
; Yang Z
; Grimm C
; Jin M
J Neurosci
2016[May]; 36
(21
): 5808-19
PMID27225770
show ga
RPE65, an abundant membrane-associate protein in the retinal pigment epithelium
(RPE), is a key retinoid isomerase of the visual cycle necessary for generating
11-cis-retinal that functions not only as a molecular switch for activating cone
and rod visual pigments in response to light stimulation, but also as a chaperone
for normal trafficking of cone opsins to the outer segments. Many mutations in
RPE65 are associated with Leber congenital amaurosis (LCA). A R91W substitution,
the most frequent LCA-associated mutation, results in a severe decrease in
protein level and enzymatic activity of RPE65, causing cone opsin mislocalization
and early cone degeneration in the mutation knock-in mouse model of LCA. Here we
show that R91W RPE65 undergoes ubiquitination-dependent proteasomal degradation
in the knock-in mouse RPE due to misfolding. The 26S proteasome non-ATPase
regulatory subunit 13 mediated degradation specifically of misfolded R91W RPE65.
The mutation disrupted membrane-association and colocalization of RPE65 with
lecithin:retinol acyltransferase (LRAT) that provides the hydrophobic substrate
for RPE65. Systemic administration of sodium 4-phenylbutyrate (PBA), a chemical
chaperone, increased protein stability, enzymatic activity, membrane-association,
and colocalization of R91W RPE65 with LRAT. This rescue effect increased
synthesis of 11-cis-retinal and 9-cis-retinal, a functional iso-chromophore of
the visual pigments, led to alleviation of S-opsin mislocalization and cone
degeneration in the knock-in mice. Importantly, PBA-treatment also improved
cone-mediated vision in the mutant mice. These results indicate that PBA, a U.S.
Food and Drug Administration-approved safe oral medication, may provide a
noninvasive therapeutic intervention that delays daylight vision loss in patients
with RPE65 mutations. SIGNIFICANCE STATEMENT: LCA is a severe early onset retinal
dystrophy. Recent clinical trials of gene therapy have implicated the need of an
alternative or combination therapy to improve cone survival and function in
patients with LCA caused by RPE65 mutations. Using a mouse model carrying the
most frequent LCA-associated mutation (R91W), we found that the mutant RPE65
underwent ubiquitination-dependent proteasomal degradation due to misfolding.
Treatment of the mice with a chemical chaperone partially corrected stability,
enzymatic activity, and subcellular localization of R91W RPE65, which was also
accompanied by improvement of cone survival and vision. These findings identify
an in vivo molecular pathogenic mechanism for R91W mutation and provide a
feasible pharmacological approach that can delay vision loss in patients with
RPE65 mutations.
|Animals
[MESH]
|Blindness/metabolism/pathology/*prevention & control
[MESH]