Cellular localization and tissue distribution of polycystin-1

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the formation of fluid-filled cysts in both kidneys, in addition to a variety of extra-renal manifestations. The PKD1 gene product, polycystin-1, encodes a novel protein with a putative role in cell-cell/cell-matrix interactions. The present study we focused on the (sub)cellular localization of polycystin-1 in cultured cells, and on its tissue distribution in various organs. In Madin Darby canine kidney (MDCK) cells, several polyclonal antibodies showed intense staining at the sites of interaction between adjacent cells, which remained after Triton extraction. Weak cytoplasmic staining was observed. No signal was detected at the free borders of cell aggregates, supporting a role for polycystin-1 in cell-cell interactions. At the tissue level, polycystin-1 expression was observed in specific cell types in tissues with known manifestations of the disease, but also in tissues of organs which have not been reported to be affected in ADPKD. Expression was frequently seen in epithelia, but also in endocrine cells (pancreatic islets, parathyroid-producing cells, clusters in the adenohypophysis, clusters in the adrenal gland, and Leydig cells in the testis). In addition, expression was observed in myocardium and more weakly in myocytes of cardiac valves, of the cerebral arteries, and of skeletal muscles.