Novel PN7718 protein and nucleic acids encoding PN7718 are provided. PN7718-containing protein complexes formed by PN7718 and a PN7718-interacting protein (e.g., cyclophilin C) are also provided. Cyclophilin C and PN7718 may be involved in common biological processes such as intracellular calcium signaling, beta-amyloid formation, T-cell receptor and IgE receptor signaling pathways, and protein folding and degradation. Thus, the protein complexes as well as PN7718 can be used in screening assays to select modulators of PN7718 and the protein complexes formed by PN7718 and cyclophilin C. The identified modulators can be useful in modulating the functions and activities of PN7718 and protein complexes containing PN7718, and in treating and preventing autoimmune diseases, neurological diseases and cardiovascular disorders.