Polycystin-1, the product of the polycystic kidney disease 1 gene, co-localizes with desmosomes in MDCK cells

Polycystin-1 is a novel protein predicted to be a large membrane-spanning g lycoprotein with an extracellular N-terminus and an intracellular C-terminu s, harboring several structural motifs, To study the subcellular localizati on, antibodies raised against various domains of polycystin-1 and against s pecific adhesion complex proteins were used for two-color immunofluorescenc e staining. In Madine Darby canine kidney (MDCK) cells, polycystin-1 was de tected in the cytoplasm as well as co-localizing with desmosomes, but not w ith tight or adherens junctions. Using confocal laser scanning and immunoel ectron microscopy we confirmed the desmosomal localization. By performing a calcium switch experiment, we demonstrated the sequential reassembly of ti ght junctions, subsequently adherens junctions and finally desmosomes, Poly cystin-1 only stained the membrane after incorporation of desmoplakin into the desmosomes, suggesting that membrane-bound polycystin-1 may be importan t for cellular signaling or cell adhesion, but not for the assembly of adhe sion complexes.