Cancer-associated retinopathy (CAR) is an ocular manifestation of a paraneoplastic syndrome whereby immunological reactions toward recoverin (Rec), a retina-specific Ca2+ binding protein, and its aberrant expression in tumor cells lead to the retinal degeneration. To elucidate functional roles of the aberrantly expression in cancer cells, we performed immunoprecipitation using antihuman Rec mAb. We observed co-precipitation of G-protein-coupled receptor kinases (GRKs) and caveolin-1 with Rec from cell lysates of 293 or SSTW cells. Immunocytochemistry revealed that immunoreactivities toward Rec within the cancer cells were almost identical to those toward GRKs and caveolin-1. The present data strongly suggest that aberrantly expressed Rec should be involved in the GRK-dependent cellular regulation in cancer cells. (C) 2002 Elsevier Science (USA). All rights reserved.