Constitutively inactive PPiase, which becomes active when bound to calmodulin and calcium. Seems to act as a chaperone for BCL2, targets it to the mitochondria and modulates its phosphorylation state. The BCL2/FKBP8/calmodulin/calcium complex probably interferes with the binding of BCL2 to its targets. The active form of FKBP8 may therefore play a role in the regulation of apoptosis (By similarity). Required for normal embryonic development. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Homomultimers or heteromultimers (Potential). Forms heterodimer with calmodulin. When activated by calmodulin and calcium, interacts with the BH4 domain of BCL2 and weakly with BCLX isoform Bcl-X(L). Does not bind and inhibit calcineurin (By similarity). Interacts with ZFYVE27; may negatively regulate ZFYVE27 phosphorylation (By similarity). Detected throughout the embryonic body, in caudal neural tube, limbs and head. Detected in adult retina, brain, heart, kidney, liver, pancreas, lung, testis and urinary bladder (at protein level). Detected in adult brain, kidney, liver, testis and trigeminal nerve, and in embryo. Detected at lower levels in lung, spleen, heart and ovary. Widely expressed in forebrain. Detected in the Purkinje cell layer in the cerebellum and in hippocampus neurons. Ubiquitinated by PRKN during mitophagy, leading to its degradation and enhancement of mitophagy. Deubiquitinated by USP30. Mice die shortly after birth. They display neural tube and skeletal defects. The neuroepithelium is disorganized and the formation of dorsal root ganglia is defective, likely as a result of an increased frequency of apoptosis and aberrant migration of neuronal cells. The extension of nerve fibers in the spinal cord is also abnormal. Binds the immunosuppressant FK506 only in its calmodulin/calcium activated form.