AN ANALYSIS OF THE EXPRESSION OF CYCLOPHILIN-C REVEALS TISSUE RESTRICTION AND AN INTRIGUING PATTERN IN THE MOUSE KIDNEY

Cyclophilin C (cyp C) is a cyclosporin A (CsA) binding protein origina lly isolated from a mouse bone marrow stromal cell line. We have compa red the expression patterns of the mammalian cyclophilins A, B, and C in mouse tissues using in situ hybridization. These studies reveal tha t cyp C is expressed in a restricted subset of tissues including mouse ovary, testis, bone marrow, and kidney. Within the kidney, cyp C is h ighly expressed in a narrow zone in the outer medulla. Using monoclona l antibodies reactive against cyp C, we find that the kidney cells exp ressing cyp C correspond to the S3 segment of the nephron The S3 segme nt has been shown to sustain histopathological damage from high dosage s of CsA, raising the possibility that cyp C may be involved in mediat ing this damage.