Identification of RPE65 in transformed kidney cells

The protein RPE65 has an important role in retinoid processing and/or retin oid transport in the eye, Retinoids are involved in cell differentiation, e mbryogenesis and carcinogenesis. Since the kidney is known as an important site for retinoid metabolism, the expression of RPE65 in normal kidney and transformed kidney cells has been examined, The RPE65 mRNA was detected in transformed kidney cell lines including the human embryonic kidney cell lin e HEK293 and the African green monkey kidney cell lines COS-1 and COS-7 by reverse transcription PCR, In contrast, it was not detected in human primar y kidney cells or monkey kidney tissues under the same PCR conditions. The RPE65 protein was also identified in COS-7 and HEK293 cells by Western blot analysis using a monoclonal antibody to RPE65, but not in the primary kidn ey cells or kidney tissues. The RPE65 cDNA containing the full-length encod ing region was amplified from HEK293 and COS-7 cells. DNA sequencing showed that the RPE65 cDNA from HEK293 cells is identical to the RPE65 cDNA from the human retinal pigment epithelium. The RPE65 from COS-7 cells shares 98 and 99% sequence identity with human RPE65 at the nucleotide and amino acid levels, respectively. Moreover, the RPE65 mRNA was detected in three out o f four renal tumor cultures analyzed including congenital mesoblastic nephr oma and clear cell sarcoma of the kidney. These results demonstrated that t ransformed kidney cells express this retinoid processing protein, suggestin g that these transformed tells may have an alternative retinoid metabolism not present in normal kidney cells. (C) 1999 Federation of European Biochem ical Societies.