Polarity of prostate specific membrane antigen, prostate stem cell antigen, and prostate specific antigen in prostate tissue and in a cultured epithelial cell line

BACKGROUND. Madin-Darby canine kidney (MDCK) cells are immortalized epithelial cells that have been used extensively as a model system to study intracellular molecular trafficking, polarized expression, and secretion of proteins in various epithelia. In order to determine if MDCK cells might serve as a model to study molecular events within prostate epithelial cells, we have evaluated the polarized distribution of three prostate restricted proteins, PSMA, PSCA, and PSA, in situ, and in MDCK cells. METHODS. Using immunofluorescence, confocal microscopy, cell surface biotinylation, antibody internalization, and biochemical assays we evaluated surface expression and secretion of three prostate restricted proteins expressed in MDCK cells. We compared these patterns of expression to results observed within prostatic epithelium. RESULTS. We demonstrate that PSMA is localized primarily to the apical plasma membrane in both the prostatic epithelium and transfected MDCK cells, whereas PSCA is expressed in a non-polarized fashion. We also show that PSA is secreted predominantly from the apical surface of transfected MDCK cells, consistent with in vivo observations. CONCLUSIONS. Similar patterns of localization among MDCK and prostatic epithelial cells suggest that the mechanisms of polarized sorting within these cell types are conserved. Thus, MDCK cells offer a useful model system to study mechanisms of targeting of these proteins within the prostate. (C) 2003 Wiley-Liss, Inc.