Recoverin, but not visinin, is an autoantigen in the human retina identified with a cancer-associated retinopathy.
OBJECTIVE
We investigated the hypothesis that visinin, a cone-specific protein first characterized in chicken retina, is a cone homologue of recoverin and may be the cancer-associated retinopathy (CAR) autoantigen in human cone cells.


METHODS
Visinin was purified from chicken retinas and tested for binding by CAR antisera. In addition, antibodies specific to visinin were used immunocytochemically and for Western analysis to determine whether visinin is present in human or bovine retinas. Anti-peptide antibodies against recoverin were used immunocytochemically to localize recoverin to mammalian cone cells.


RESULTS
CAR antisera recognized recoverin but not visinin. Furthermore, visinin could not be detected in mammalian retinas by immunocytochemical methods or by attempts to purify the protein. In contrast to visinin, antibodies specific for different regions of the recoverin molecule stained both rod and cone cells in the human retina.


CONCLUSIONS
Visinin is not the CAR autoantigen in human cone cells. Differences between recoverin and visinin probably reflect species differences rather than rod-cone differences. Recoverin, or a nearly identical molecule, is present in mammalian cones and likely is the cone cell CAR autoantigen.
Polans
A S
AS
R.S. Dow Neurological Sciences Institute, GSH&MC, Portland, OR 97209.
Burton
M D
MD
Haley
T L
TL
Crabb
J W
JW
Palczewski
K
K
D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm / Q000032:analysis* / Q000302:isolation & purification; D001324:Autoantigens / Q000032:analysis*; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000302:isolation & purification; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000032:analysis* / Q000302:isolation & purification; D002417:Cattle; D002645:Chickens; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D005136:Eye Proteins / Q000032:analysis / Q000302:isolation & purification; D051597:Hippocalcin; D006801:Humans; D008074:Lipoproteins; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000032:analysis* / Q000302:isolation & purification; D010786:Photoreceptor Cells / Q000737:chemistry; D011817:Rabbits; D051603:Recoverin; D012160:Retina / Q000737:chemistry*; D013045:Species Specificity
D000951:Antigens, Neoplasm; D001324:Autoantigens; D014408:Biomarkers, Tumor; D002135:Calcium-Binding Proteins; D005136:Eye Proteins; D008074:Lipoproteins; D009419:Nerve Tissue Proteins; C496731:RCVRN protein, human; C045140:visinin; D051603:Recoverin; D051597:Hippocalcin