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Not So Hot Rods:
Mutations of Rhodopsin Kinase in Regards to Oguchi Disease
J. Bade, C. Czerniak, S. Daley, A. Kellicut, J. Killoren, E. Krupski, L. Semler, C. Wilkins
Teacher: Mark Arnholt
Mentor: Melissa Wilk, B.S., Medical College of Wisconsin
Abstract
The average person’s eyes adapt to darkness within minutes. For those with Oguchi disease,
adaptation can be slowed to several hours. Oguchi disease is an autosomal recessive
disorder that results in greatly slowed phototransduction. Phototransduction is a cascade
reaction beginning with a photon activating rhodopsin in the rod and leading to
hyperpolarization of the cell. Oguchi disease is caused by mutations in rhodopsin kinase
which prevent the phosphorylation of rhodopsin, lowering rhodopsin’s affinity for arrestin. This
reduced ability to bind arrestin decreases the speed in which rhodopsin is deactivated and
prepped to reactivate. After a long period in a dark environment, the rhodopsin is eventually
deactivated by arrestin, allowing it to be recycled. The Hartford Union High School SMART
(Students Modelling a Research Topic) Team has designed a model of rhodopsin kinase to
investigate its structure-function relationship. Oguchi disease can be caused by two different
mutations in rhodopsin kinase: large deletion or point mutation. In our 3D model, we will
highlight the complete deletion of exon five, the partial deletion at the C-terminus, and point
mutations in the catalytic domain (Val380Asp and Pro391His) that cause Oguchi disease.
Understanding the structure-function relationships of rhodopsin kinase could shed more light
on night blindness. This program is supported by a grant from NIH and CTSA.
Function of Rhodopsin Kinase
When a photon of light enters the eye, phototransduction, the process enabling us to
see, begins. Within the rod photoreceptors, the cells responsible for night vision, the
photon activates rhodopsin, stimulating a cascade of neural events resulting in the
recognition of light. Following activation of rhodospin, a protein called rhodopsin
kinase is responsible for deactivating rhodopsin so that it can be recycled for another
round of activation. During phototransduction, calcium levels decrease, allowing
recoverin, a calcium-binding protein, to release rhodopsin kinase. Rhodopsin kinase
then uses ATP to phosphorylate the activated rhodopsin. Once phosphorylated,
arrestin binds the rhodopsin, fully deactivating it and allowing for the recycling of
retinal within the rhodopsin. Without the rhodopsin kinase, the rhodopsin cannot be
recycled properly, resulting in slowed dark adaptation.
Structure of Rhodopsin Kinase
Oguchi Disease
Oguchi Disease is caused by mutations in rhodopsin kinase which result in
greatly slowed adaptation of the rods of the retina. For a person living with
this disease, the adaption to the dark will take several hours, whereas a
person without the disease, adaption will only take several minutes. This
makes everyday tasks such as driving at night, navigating a dark room,
and going into a dimly lit restaurant difficult. Patients with Oguchi Disease
have a distinct fundus appearance, with a golden sheen under light
adapted states (left) that disappears with dark adaption (right).
Model of Rhodopsin Kinase based on file 3C51.pdb
● A phosphate binding loop is formed by the Glycine-rich β1-β2 turn. It directly interacts with the triphosphate
tail of ATP and helps stabilize the phosphorylation transition state.
● The N-terminal amino acid residues 8-17 of rhodopsin kinase appear to be critical for rhodopsin
phosphorylation and recoverin binding.
● Point mutations Val380Asp and Pro391His in catalytic domain, as well as a deletion of exon 5, disrupt the
normal function of rhodopsin kinase, resulting in slowed dark adaptation.
Mutations in Rhodopsin Kinase
Summary
One of three mutations in the rhodopsin kinase gene cause Oguchi
disease: a point mutation, two point mutations in the catalytic domain, or a
complete deletion of exon 5. PCR can be used to identify the exon 5
deletion of this protein. Rhodopsin kinase is involved in the process of
phototransduction in the rods of the retina where it works to prepare the
rod to accept another photon of light. The specific mutations alter the
shape of rhodopsin kinase and ultimately slow down the process of
adaptation to a lack of light by nine times[1]. Oguchi disease is the
condition of slowed adaptation to darkness. Understanding the underlying
cause of Oguchi disease may help in the development of future treatments
for this debilitating disease.
References
Oguchi disease is typically caused by one of three mutations in the rhodopsin kinase gene: point mutations in
the Val380Asp or Pro391His, or a total deletion of exon 5. Cideciyan and other used polymerase chain reaction
(PCR) to amplify the rhodopsin kinase gene with and without an exon 5 deletion. Different primers were used to
pinpoint the exons, then the DNA fragments were run through the gel. In gel electrophoresis, strands that travel
further toward the negative end are shorter, and strands that stay closer to the positive end are longer. The
results of the gel electrophoresis show a complete absence of the exon 5 sequence in lane one.
The largest mutation that causes Oguchi disease is the complete deletion of exon
5, a 1.7 kb deletion that removes 42 amino acids from the protein. This greatly
alters the shape of the protein, making it inert and therefore slowing down the rate
of rhodopsin deactivation.
There are also two point mutations in the catalytic domain that can cause Oguchi
disease, Val380Asp and Pro391His. These mutations reside in exon 5, and are
involved in phosphorylating rhodopsin to help deactivate it.
Another point mutation, at amino acid 334, not in the catalytic domain, has been
known to also cause Oguchi disease.
1. Cideyciyan, A.V., Zhao, X., Nielsen, L., Khani, S.C., Jacobson, S.G.,
Palcaewski, K. (1997). Null mutation in the rhodopsin kinase gene
slows recovery kinetics of rod and cone phototransduction in man.
Proc. Natl. Acad. Sci. USA, 95(1): 328-333.
1. Baylor, D.A., Burns, M.E. (1998). Control of rhodopsin activity in
vision. Eye, 12(Pt 3b): 521-525.
1. Singh, P., Wang, B., Maeda, T., Palczewski, K., Tesmer, J.J.G. (2008).
Structures of rhodopsin kinase in different ligand states reveal key
elements involved in G protein-coupled receptor kinase activation. J
Biol Chem, 283(20): 14053-14062.
SMART Teams are supported by the National Center for Advancing Translational
Sciences, National Institutes of Health, through Grant Number 8UL1TR0C0055.
Its contents are solely the responsibility of the author and do not necessarily represent the
official views of the NIH.