Trafficking of Membrane-Associated Proteins to Cone Photoreceptor Outer Segments Requires the Chromophore 11-<i>cis</i>-Retinal

Zhang, Houbin; Fan, Jie; Li, Sha; Karan, Sukanya; Rohrer, Bäerbel; Palczewski, Krzysztof; Frederick, Jeanne M.; Crouch, Rosalie K.; Baehr, Wolfgang

doi:10.1523/jneurosci.0317-08.2008

Cited by 94 publications

(127 citation statements)

References 33 publications

Supporting

Mentioning

112

Contrasting

Order By: Relevance

“…The role(s) played by RPE65 in providing chromophore for cone function and/or survival remains unclear and controversial (1,3,40,(43)(44)(45)(46)(47)(48)(49). Restoration of cone-as well as rod photoreceptor-based visual function by subretinal AAV gene therapy in the canine model of RPE65-LCA (4,8), together with the existence of remnant cone function in patients with untreated RPE65-LCA (3), suggested a potential to improve cone function in patients undergoing gene therapy.…”

Section: Discussionmentioning

confidence: 99%

Human gene therapy for RPE65 isomerase deficiency activates the retinoid cycle of vision but with slow rod kinetics

Cideciyan

Alemán

Boye

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

609

515

View full text Add to dashboard Cite

The RPE65 gene encodes the isomerase of the retinoid cycle, the enzymatic pathway that underlies mammalian vision. Mutations in RPE65 disrupt the retinoid cycle and cause a congenital human blindness known as Leber congenital amaurosis (LCA). We used adeno-associated virus-2-based RPE65 gene replacement therapy to treat three young adults with RPE65-LCA and measured their vision before and up to 90 days after the intervention. All three patients showed a statistically significant increase in visual sensitivity at 30 days after treatment localized to retinal areas that had received the vector. There were no changes in the effect between 30 and 90 days. Both cone-and rod-photoreceptor-based vision could be demonstrated in treated areas. For cones, there were increases of up to 1.7 log units (i.e., 50 fold); and for rods, there were gains of up to 4.8 log units (i.e., 63,000 fold). To assess what fraction of full vision potential was restored by gene therapy, we related the degree of light sensitivity to the level of remaining photoreceptors within the treatment area. We found that the intervention could overcome nearly all of the loss of light sensitivity resulting from the biochemical blockade. However, this reconstituted retinoid cycle was not completely normal. Resensitization kinetics of the newly treated rods were remarkably slow and required 8 h or more for the attainment of full sensitivity, compared with <1 h in normal eyes. Cone-sensitivity recovery time was rapid. These results demonstrate dramatic, albeit imperfect, recovery of rod-and cone-photoreceptor-based vision after RPE65 gene therapy. dark adaptation ͉ photoreceptor ͉ retinal degeneration ͉ retinoid cycle T he enzymatic pathway in the human eye that regenerates light-altered vitamin A molecules is known as the retinoid cycle of vision. Molecular defects in retinoid cycle genes can lead to inherited retinal diseases in man (1). The severity of visual disturbance in these diseases is thought to be related to how the mutation alters the biochemical activity and whether there is redundancy at the multiple biochemical steps of the cycle. A severe form of incurable childhood blindness, Leber congenital amaurosis (LCA), is caused by mutations in RPE65 (retinal pigment epithelium-specific protein, 65 kDa), the gene in the retinal pigment epithelium (RPE) that encodes the isomerase. This is the only known enzyme that catalyzes isomerization of all-trans-retinyl esters to 11-cis-vitamin A. In RPE65 deficiency, photoreceptor cells do not regenerate their visual pigment and vision is not sustained. Retinal anatomy also degenerates, but not entirely (2, 3).RPE65-deficient animals have been characterized, and proofof-principle studies using recombinant adeno-associated virus (AAV) vector delivery of RPE65 to RPE cells have described restoration of vision (2,(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). These studies provided the impetus for human safety studies of RPE65 gene replacement (trials NCT00481546, NCT00643747, NCT00516477, and NCT00422721, www.clinicaltri...

show abstract

Section: Discussionmentioning

confidence: 99%

Human gene therapy for RPE65 isomerase deficiency activates the retinoid cycle of vision but with slow rod kinetics

Cideciyan

Alemán

Boye

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

609

515

View full text Add to dashboard Cite

show abstract

“…S1 comparing the ROS, rod inner segments (RIS) and outer nuclear layer (ONL) in S-opsin + Rho −/− Lrat −/− and S-opsin + Rho +/− Lrat −/− mice at age 1 mo] (16). In the above experiments, we used S-opsin + Rho +/− Lrat −/− and S-opsin + Rho +/+ Lrat −/− mice older than 1 mo in which most of the S-opsin-expressing cones had already died from the lack of chromophore, thus minimizing confounding signals from those cones (13,15,16). As a negative control for a generalized disruption of protein targeting to the ROS in the absence of chromophore and R-opsin, we also examined the localization of a rod cyclic nucleotide-gated cation channel subunit, CNGA1, a membrane protein mediating phototransduction in ROS.…”

Section: Significancementioning

confidence: 99%

“…In vivo evidence, albeit of paramount importance, is also challenging, because rhodopsin always exists as a single isoform in rod photoreceptors, thus making homomeric, higher-order complexes difficult to distinguish from monomers. We addressed this question by taking advantage of the unique opportunity provided by a mouse line (S-opsin + Lrat −/− ) that expresses transgenically the short wavelength-sensitive cone opsin (S-opsin) in rods and by exploiting the fact that cone opsins, but not the apoprotein of rhodopsin R-opsin, require chromophore for proper folding and trafficking to the photoreceptor's outer segment (13)(14)(15)(16)(17). Our work shows that: (i) rhodopsin, and by extension cone pigments, natively mature in vivo in the endoplasmic reticulum (ER) as dimers and traffic as such to the outer segment; (ii) in S-opsin + Lrat −/− transgenic rods, R-opsin helps S-opsin fold and traffic by forming heterodimers with it; and (iii) the H1 and H8 helices are important for pigment dimerization.…”

mentioning

confidence: 99%

Dimerization of visual pigments in vivo

Zhang

Cao

Kumar

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

It is a deeply engrained notion that the visual pigment rhodopsin signals light as a monomer, even though many G protein-coupled receptors are now known to exist and function as dimers. Nonetheless, recent studies (albeit all in vitro) have suggested that rhodopsin and its chromophore-free apoprotein, R-opsin, may indeed exist as a homodimer in rod disk membranes. Given the overwhelmingly strong historical context, the crucial remaining question, therefore, is whether pigment dimerization truly exists naturally and what function this dimerization may serve. We addressed this question in vivo with a unique mouse line (S-opsin + Lrat −/− ) expressing, transgenically, short-wavelength-sensitive cone opsin (S-opsin) in rods and also lacking chromophore to exploit the fact that cone opsins, but not R-opsin, require chromophore for proper folding and trafficking to the photoreceptor's outer segment. In R-opsin's absence, S-opsin in these transgenic rods without chromophore was mislocalized; in R-opsin's presence, however, S-opsin trafficked normally to the rod outer segment and produced functional S-pigment upon subsequent chromophore restoration. Introducing a competing R-opsin transmembrane helix H1 or helix H8 peptide, but not helix H4 or helix H5 peptide, into these transgenic rods caused mislocalization of R-opsin and S-opsin to the perinuclear endoplasmic reticulum. Importantly, a similar peptidecompetition effect was observed even in WT rods. Our work provides convincing evidence for visual pigment dimerization in vivo under physiological conditions and for its role in pigment maturation and targeting. Our work raises new questions regarding a potential mechanistic role of dimerization in rhodopsin signaling.rhodopsin | cone opsin | dimerization | protein trafficking R hodopsin and cone pigments mediate scotopic and photopic vision, respectively. They consist of opsin, the apo-protein, and 11-cis-retinal, a vitamin A-based chromophore. Light absorption by 11-cis-retinal triggers a conformational change in opsin, which in turn initiates a G protein-coupled receptor (GPCR) signaling pathway to lead to vision. Indeed, rhodopsin signaling is a prominent prototypical GPCR pathway from which a huge quantity of mechanistic details about such signaling in general has emerged. All along, it is a dogma that rhodopsin exists and functions as a monomer (1-6). About a decade ago, evidence began to emerge that rhodopsin may exist as a dimer, based on atomic force microscopy and cross-linking experiments performed on rod outersegment (ROS) disk membranes (7-9). However, this concept remains highly controversial because of the lack of in vivo evidence and also is puzzling because, unlike many GPCRs, monomeric rhodopsin is fully functional with respect to coupling to G protein (2, 4-6, 10) and to interactions with rhodopsin kinase and arrestin (11,12). In vivo evidence, albeit of paramount importance, is also challenging, because rhodopsin always exists as a single isoform in rod photoreceptors, thus making homomeric, higher-or...

show abstract

“…The proteins comprising the POS discs are made in the inner segment (IS) on the rough endoplasmic reticulum (ER) followed by post-translational modifications that occur in the ER and Golgi apparatus (22,23). Newly synthesized OS proteins must transport to OS through the connecting cilium (24).…”

mentioning

confidence: 99%

Impaired Association of Retinal Degeneration-3 with Guanylate Cyclase-1 and Guanylate Cyclase-activating Protein-1 Leads to Leber Congenital Amaurosis-1

Zulliger

Naash

Rajala

et al. 2015

Journal of Biological Chemistry

View full text Add to dashboard Cite

Background: Defects in the function of guanylate cyclase 1 (GC1) cause Leber congenital amaurosis (LCA) type 1. Results: GC1, GCAP1, and RD3 form a complex in the endoplasmic reticulum that targets GC1 to outer segments. Conclusion: A subset of LCA1 is caused by impaired formation of the RD3-GC1-GCAP1 complex. Significance: Understanding the molecular interaction of RD3 with GC1 and GCAP1 has potential therapeutic benefits for LCA1.

show abstract

Trafficking of Membrane-Associated Proteins to Cone Photoreceptor Outer Segments Requires the Chromophore 11-cis-Retinal

Cited by 94 publications

References 33 publications

Human gene therapy for RPE65 isomerase deficiency activates the retinoid cycle of vision but with slow rod kinetics

Human gene therapy for RPE65 isomerase deficiency activates the retinoid cycle of vision but with slow rod kinetics

Dimerization of visual pigments in vivo

Impaired Association of Retinal Degeneration-3 with Guanylate Cyclase-1 and Guanylate Cyclase-activating Protein-1 Leads to Leber Congenital Amaurosis-1

Contact Info

Product

Resources

About