Along with PPIB, PPIC localizes to the endoplasmic reticulum (ER), where it maintains redox homeostasis. Depletion of these two cyclophilins lead to hyperoxidation of the ER. In the brain, PPIC complexes with cyclophilin C-associated protein (CyCAP) to activate microglia and macrophage function via the calcineurin/NFAT pathway. As a cyclophilin, PPIC binds the immunosuppressive drug CsA to form a CsA-cyclophilin complex, which then targets calcineurin to inhibit the signaling pathway for T-cell activation. In cardiac myogenic cells, cyclophilins have been observed to be activated by heat shock and hypoxia-reoxygenation as well as complex with heat shock proteins. Thus, cyclophilins may function in cardioprotection during ischemia-reperfusion injury. Similarly, PPIC may confer neuroprotection by forming a complex with CyCAP to activate survival mechanisms and mitigate ischemic damage in the brain. Currently, cyclophilin expression is highly correlated with cancer pathogenesis, but the specific mechanisms remain to be elucidated. For instance, studies identify PPIC as a reliable indicator of circulating tumor cells in epithelial ovarian cancer (EOC) and, thus, may serve as a biomarker for detection and treatment of the cancer. PPIC has been shown to interact with: