Pathological roles of recoverin in cancer-associated retinopathy.

Cancer associated retinopathy (CAR) is an ocular manifestation of paraneoplastic syndrome clinically characterized by progressive visual impairment similar to retinitis pigmentosa. As a possible mechanism causing the retinal degeneration, the presence of serum autoantibodies against recoverin and other retinal antigens are involved. The molecular pathology in CAR by anti-recoverin antibody is considered to occur in the following steps: Firstly, recoverin aberrantly expressed in cancerous tissues is recognized by immunocytes by some unknown mechanisms and then a specific antibody toward recoverin is produced. Secondly, the anti-recoverin antibody reaches the retina via the peripheral circulation and is taken up into photoreceptor cells. Lastly, the antibody blocks recoverin function (inhibition of rhodopsin phosphorylation in a calcium dependent manner), and enhancement of rhodopsin phosphorylation induces retinal apoptosis.