There are suggestions of polycystin-2 functioning in different cellular locations:
Polycystin-2 associated with polycystin-1 gates Ca2+ entry across the plasma membrane.
In the case of mechanosensitive cilia in kidney cells, the primary entry of external Ca2+ is amplified by releasing further Ca2+ from the endoplasmic reticulum either through ryanodine receptors (RYRs) or through inositol 1,4,5-trisphosphate receptors (InsP3Rs).
There is a suggestion that polycystin-1 located in the plasma membrane may be associated with, and regulates the release of internal Ca2+ by, polycystin-2 located in the endoplasmic reticulum.
Polycystin-2 located in the endoplasmic reticulum may be stimulated to release Ca2+ through a Ca2+-induced Ca2+ release (CICR) mechanism using the Ca2+ released through InsP3.