Functional cross-talk between the TSC2 gene product, Tuberin and the PKD1 gene product, polycystin-1. Evidence published to date suggests that PC-1 trafficking from the Golgi compartment to cell-cell junctions requires Tuberin . The role of Tuberin in PC-1 trafficking to the primary cilium was not investigated. In addition, PC-1 can regulate the mTORC1 cascade by regulating the phosphorylation and activity of Tuberin (A) . Furthermore, a physical interaction was described between the portion of the PC-1 cytoplasmic C-terminal tail most proximal to the last transmembrane domain and Tuberin . The PC-1/Tuberin interaction might be necessary for the correct trafficking of PC-1 or for regulation of mTORC1 (B, see text). Future studies should focus on providing experimental evidence of the significance of this interaction. One final possibility is that PC-1 and Tuberin cross-talk at several levels.