Polycystin-1 and polycystin-2 are involved in autosomal dominant polycystic kidney disease (ADPKD) by unknown mechanisms. These two proteins are located in primary cilia where they mediate mechanosensation, suggesting a link between cilia function and renal disease. In this study we sought to characterize the subcellular localization of polycystin-L, a closely related member of polycystin-2, in epithelial renal cell lines. We have shown that endogenous polycystin-L subcellular distribution is different in proliferative and non-proliferative cultures. Polycystin-L is found mostly in the endoplasmic reticulum in subconfluent cell cultures while in confluent cells it is redistributed to sites of cell-cell contact and to the primary cilium as is polycystin-1. Subcellular fractionation confirmed a common distribution of polycystin-L and polycystin-1 in the fractions corresponding to those containing the plasma membrane of post-confluent cells. Reciprocal co-immunoprecipitation experiments showed that polycystin-L was associated with polycystin-1 in a common complex in both subconfluent and confluent cell cultures. Interestingly, we also identified a novel site for a polycystin member (polycystin-L) in unciliated cells, the centrosome, which allowed us to reveal an involvement of polycystin-L in cell proliferation.