Taken all together, we propose that as in kidney cysts, in KV cells the drop of the intracellular Ca2+ levels caused by the knockdown of Polycystin-2, leads to the activation of AC5 and AC6 and to the inhibition of PDE1A, raising the levels of cAMP and, thus, activating CFTR (Fig. 5D). Here, PDE1A is linked to Kidney Cyst.