FKBP12 is a member of the family of soluble receptors capable of binding to one of two major immunosuppressant agents. FKBP12 also plays a role in intracellular calcium regulation by associating with three types of calcium release channel complexes, cardiac and skeletal ryanodine receptors and the inositol 1,4,5-trisphosphate receptor. In interactions with members of the TGF beta family type I receptors, FKBP12 has been shown to exert an inhibitory effect on the signaling pathway.