Reserpine maintains photoreceptor survival in retinal ciliopathy by resolving proteostasis imbalance and ciliogenesis defects

Abstract

Ciliopathies manifest from sensory abnormalities to syndromic disorders with multiorgan pathologies, with retinal degeneration a highly penetrant phenotype. Photoreceptor cell death is a major cause of incurable blindness in retinal ciliopathies. To identify drug candidates to maintain photoreceptor survival, we performed an unbiased, high-throughput screening of over 6,000 bioactive small molecules using retinal organoids differentiated from induced pluripotent stem cells (iPSC) of rd16 mouse, which is a model of Leber congenital amaurosis (LCA)10 caused by mutations in the cilia-centrosomal gene CEP290. We identified five non-toxic positive hits, including the lead molecule reserpine, which improved photoreceptor survival in rd16 organoids. Reserpine also maintained photoreceptors in retinal organoids derived from induced pluripotent stem cells of LCA10 patients and in rd16 mouse retina in vivo. Reserpine-treated patient organoids revealed modulation of signaling pathways related to cell survival/death, metabolism, and proteostasis. Further investigation uncovered misregulation of autophagy associated with compromised primary cilium biogenesis in patient organoids and rd16 mouse retina. Reserpine partially restored the balance between autophagy and the ubiquitin-proteasome system, at least in part by increasing the cargo adaptor p62 and improving primary cilium assembly. Our study identifies effective drug candidates in preclinical studies of CEP290 retinal ciliopathies through cross-species drug discovery using iPSC-derived organoids, highlights the impact of proteostasis in the pathogenesis of ciliopathies, and provides new insights for treatments of retinal neurodegeneration.

Pathways controlling neurotoxicity and proteostasis in mitochondrial complex I deficiency

“…Alterations in the ubiquitin/proteasome and autophagy/lysosome systems have been documented in various genetic forms of retinal degeneration and in other aging-dependent ocular diseases (54,55), as has oxidative stress and mitochondrial dysfunction (42,43), suggesting fundamental connections among these pathways. A functionally important relationship between altered proteostasis and photoreceptor vulnerability was recently suggested by a chemical screening approach in an induced pluripotent stem cell-derived model of retinal degeneration caused by genetic ciliary dysfunction, which identified reserpine as both promoting photoreceptor survival and normalizing proteostasis (56).…”