Abstract
The retina-specific ATP binding cassette transporter, ABCA4 protein, is associated with a broad range of inherited macular degenerations, including Stargardt disease, autosomal recessive cone rod dystrophy, and fundus flavimaculatus. In order to understand its role in retinal transport in rod out segment discs, we have investigated the interactions of the soluble domains of ABCA4 with both 11-cis- and all-trans-retinal. Using fluorescence anisotropy-based binding analysis and recombinant polypeptides derived from the amino acid sequences of the four soluble domains of ABCA4, we demonstrated that the nucleotide binding domain 1 (NBD1) specifically bound 11-cis-retinal. Its affinity for all-trans-retinal was markedly reduced. Stargardt disease-associated mutations in this domain resulted in attenuation of 11-cis-retinal binding. Significant differences in 11-cis-retinal binding affinities were observed between NBD1 and other cytoplasmic and lumenal domains of ABCA4. The results suggest a possible role of ABCA4 and, in particular, the NBD1 domain in 11-cis-retinal binding. These results also correlate well with a recent report on the in vivo role of ABCA4 in 11-cis-retinal transport.
Highlights
The ABCA4 protein is proposed to transport all-trans-retinal from the outer segment discs of retinal rod and cone photoreceptors
Using fluorescence anisotropy-based binding analysis and recombinant polypeptides derived from the amino acid sequences of the four soluble domains of ABCA4, we demonstrated that the nucleotide binding domain 1 (NBD1) bound 11-cis-retinal
We have shown earlier that NBD1 binds and hydrolyzes all ribonucleotide triphosphates, but NBD2 is specific for ATP
Summary
The ABCA4 protein is proposed to transport all-trans-retinal from the outer segment discs of retinal rod and cone photoreceptors. In order to understand its role in retinal transport in rod out segment discs, we have investigated the interactions of the soluble domains of ABCA4 with both 11-cis- and all-trans-retinal. The retina-specific ABC2 transporter, ABCA4 protein, has been linked through genetic studies to a number of inherited visual diseases, including Stargardt macular dystrophy [1, 2], fundus flavimaculatus [3,4,5,6], autosomal recessive retinitis pigmentosa (6 –11), cone-rod dystrophy [8, 12,13,14,15,16,17], and perhaps increased susceptibility to age-related macular degeneration Based on recent studies proposing a physiological role of ABCA4 that may include translocation of 11-cis-retinal across the ROS disc membrane [25] as well as preliminary studies pointing to a specific interaction of NBD1 with 11-cis-retinal [40], we posed the following question. Do the nucleotide binding domains of ABCA4 interact with retinal, and if so, how is this interaction influenced by disease-associated mutations in these domains? In this report, we have investigated the retinal binding properties of the first nucleotide binding domain of ABCA4 and examined the effects of disease-associated mutations on retinal binding
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
