Fig. 5. Ligand-induced dimerization and its applications to membrane receptors. (a) Chemical structure of rapamycin (Rap). Black or red region correspond to those interacting with FKBP or FRB, respectively. (b) Schematic illustration of intracellular heterodimerization of TGF-βRI and TGF-βRII by rapamycin. (c) Application of heterodimerization into AND logic gate for the precise control of CAR-T cell. In this system, both antigen-recognition and addition of the dimerizer are required for the signal transduction. (d) Ligand-induced translocation of Gα protein to transmembrane for dissecting its role in the heterotrimeric complex. ER, endoplasmic reticulum.