Biochemical evidence for pathogenicity of rhodopsin kinase mutations correlated with the oguchi form of congenital stationary night blindness.
Rhodopsin kinase (RK), a rod photoreceptor cytosolic enzyme, plays a key role in the normal deactivation and recovery of the photoreceptor after exposure to light. To date, three different mutations in the RK locus have been associated with Oguchi disease, an autosomal recessive form of stationary night blindness in man characterized in part by delayed photoreceptor recovery [Yamamoto, S. , Sippel, K. C., Berson, E. L. & Dryja, T. P. (1997) Nat. Genet. 15, 175-178]. Two of the mutations involve exon 5, and the remaining mutation occurs in exon 7. Known exon 5 mutations include the deletion of the entire exon sequence [HRK(X5 del)] and a missense change leading to a Val380Asp substitution in the encoded product (HRKV380D). The mutation in exon 7 is a 4-bp deletion in codon 536 leading to premature termination of the encoded polypeptide [HRKS536(4-bp del)]. To provide biochemical evidence for pathogenicity of these mutations, wild-type human rhodopsin kinase (HRK) and mutant forms HRKV380D and HRKS536(4-bp del) were expressed in COS7 cells and their activities were compared. Wild-type HRK catalyzed light-dependent phosphorylation of rhodopsin efficiently. In contrast, both mutant proteins were markedly deficient in catalytic activity with HRKV380D showing virtually no detectible activity and HRKS536(4-bp del) only minimal light-dependent activity. These results provide biochemical evidence to support the pathogenicity of the RK mutations in man.
Khani
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SC
Department of Ophthalmology, State University of New York at Buffalo, Buffalo, NY 14215, USA. skhani@ubmedh.buffalo.edu
Nielsen
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Vogt
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TM
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D005136:Eye Proteins; D051606:G-Protein-Coupled Receptor Kinase 1; D006801:Humans; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D009755:Night Blindness / Q000151:congenital* / Q000209:etiology / Q000235:genetics; D010766:Phosphorylation / Q000528:radiation effects; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012243:Rhodopsin / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D005136:Eye Proteins; D011994:Recombinant Proteins; D012243:Rhodopsin; D011494:Protein Kinases; D051606:G-Protein-Coupled Receptor Kinase 1; C496764:GRK1 protein, human