Dataset Information

Ablation of retinal ciliopathy protein RPGR results in altered photoreceptor ciliary composition.

ABSTRACT: Cilia regulate several developmental and homeostatic pathways that are critical to survival. Sensory cilia of photoreceptors regulate phototransduction cascade for visual processing. Mutations in the ciliary protein RPGR (retinitis pigmentosa GTPase regulator) are a prominent cause of severe blindness disorders due to degeneration of mature photoreceptors. However, precise function of RPGR is still unclear. Here we studied the involvement of RPGR in ciliary trafficking by analyzing the composition of photoreceptor sensory cilia (PSC) in Rpgr(ko) retina. Using tandem mass spectrometry analysis followed by immunoblotting, we detected few alterations in levels of proteins involved in proteasomal function and vesicular trafficking in Rpgr(ko) PSC, prior to onset of degeneration. We also found alterations in the levels of high molecular weight soluble proteins in Rpgr(ko) PSC. Our data indicate RPGR regulates entry or retention of soluble proteins in photoreceptor cilia but spares the trafficking of key structural and phototransduction-associated proteins. Given a frequent occurrence of RPGR mutations in severe photoreceptor degeneration due to ciliary disorders, our results provide insights into pathways resulting in altered mature cilia function in ciliopathies.

SUBMITTER: Rao KN

PROVIDER: S-EPMC4463945 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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Ablation of retinal ciliopathy protein RPGR results in altered photoreceptor ciliary composition.

Rao Kollu N KN Li Linjing L Anand Manisha M Khanna Hemant H

Scientific reports 20150611

Cilia regulate several developmental and homeostatic pathways that are critical to survival. Sensory cilia of photoreceptors regulate phototransduction cascade for visual processing. Mutations in the ciliary protein RPGR (retinitis pigmentosa GTPase regulator) are a prominent cause of severe blindness disorders due to degeneration of mature photoreceptors. However, precise function of RPGR is still unclear. Here we studied the involvement of RPGR in ciliary trafficking by analyzing the compositi ...[more]

PMID: 26068394

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Project description:The retinitis pigmentosa GTPase regulator (RPGR) and nephrocystin-4 (NPHP4) comprise two key partners of the assembly complex of the RPGR-interacting protein 1 (RPGRIP1). Mutations in RPGR and NPHP4 are linked to severe multisystemic diseases with strong retinal involvement of photoreceptor neurons, whereas those in RPGRIP1 cause the fulminant photoreceptor dystrophy, Leber congenital amaurosis (LCA). Further, mutations in Rpgrip1 and Nphp4 suppress the elaboration of the outer segment compartment of photoreceptor neurons by elusive mechanisms, the understanding of which has critical implications in uncovering the pathogenesis of syndromic retinal dystrophies. Here we show RPGRIP1 localizes to the photoreceptor connecting cilium (CC) distally to the centriole/basal body marker, centrin-2 and the ciliary marker, acetylated-?-tubulin. NPHP4 abuts proximally RPGRIP1, RPGR and the serologically defined colon cancer antigen-8 (SDCCAG8), a protein thought to partake in the RPGRIP1 interactome and implicated also in retinal-renal ciliopathies. Ultrastructurally, RPGRIP1 localizes exclusively throughout the photoreceptor CC and Rpgrip1(nmf247) photoreceptors present shorter cilia with a ruffled membrane. Strikingly, Rpgrip1(nmf247) mice without RPGRIP1 expression lack NPHP4 and RPGR in photoreceptor cilia, whereas the SDCCAG8 and acetylated-?-tubulin ciliary localizations are strongly decreased, even though the NPHP4 and SDCCAG8 expression levels are unaffected and those of acetylated-?-tubulin and ?-tubulin are upregulated. Further, RPGRIP1 loss in photoreceptors shifts the subcellular partitioning of SDCCAG8 and NPHP4 to the membrane fraction associated to the endoplasmic reticulum. Conversely, the ciliary localization of these proteins is unaffected in glomeruli or tubular kidney cells of Rpgrip1(nmf247), but NPHP4 is downregulated developmentally and selectively in kidney cortex. Hence, RPGRIP1 presents cell type-dependent pathological effects crucial to the ciliary targeting and subcellular partitioning of NPHP4, RPGR and SDCCAG8, and acetylation of ciliary ?-tubulin or its ciliary targeting, selectively in photoreceptors, but not kidney cells, and these pathological effects underlie photoreceptor degeneration and LCA.

Dataset Information

Ablation of retinal ciliopathy protein RPGR results in altered photoreceptor ciliary composition.

Publications

Ablation of retinal ciliopathy protein RPGR results in altered photoreceptor ciliary composition.

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