Immunological detection of polycystin-1 in human kidney.

Polycystin-1 is the protein product of the PKD1 gene. Mutations in this gene are responsible for most cases of polycystic kidney disease, but little is known about how these mutations lead to the development of cysts. Indeed, even less is known about the normal role of polycystin-1 in the kidney. The cellular localization of polycystin-1 has been the subject of intense investigation by many groups, including ours. In this report we describe our results and compare our data with those of others. We generated 14 different polyclonal antisera against fragments of the predicted 462-kDa polycystin-1 molecule to enable us to investigate the expression of polycystin-1 in cells and tissues by immunocytochemistry, western blotting, and immunoprecipitation. Our antibodies readily recognized a 134-kDa polycystin-1 fragment overexpressed in COS cells and stained the epithelial cells of fetal, adult, and cystic kidney sections with the same pattern as reported by others. However, further investigations revealed that this pattern was not specific for polycystin-1. We could not unequivocally detect polycystin-1 in vivo, either by immunoblotting or immunocytochemistry. Therefore our studies do not support the reported pattern of polycystin-1 expression in the kidney.