RHPN2 (rhophilin-2) binds to activated RHOB (RHOB:GTP) and relocalizes to endosomal membrane. The expression of the mouse Rhpn2 in thyrocytes increases upon TSH stimulation (Mircescu et al. 2002). This implied an important function of Rhpn2 in the thyroid, but Rhpn2 deficient mice exhibit normal thyroid structure and function, as well as an overall normal development (Behrends et al. 2005).