Identification of simian cyclophilin A as a calreticulin-binding protein in yeast two-hybrid screen and demonstration of cyclophilin A interaction with calreticulin

Cyclophilin A (CyPA) was identified as one of the calreticulin (CR)-binding proteins in a yeast two-hybrid screen utilizing simian cDNA expression-lib rary. The simian CyPA protein had 96% identity with that of human, differin g only at eight amino acid residues. We further established CyPA-CR interac tion by incubation of glutathione transferase-fused CyPA (GST-CyPA) and CR proteins with CV-1 cyto-lysates, followed by CR and CyPA-specific immune-bl ot analysis. The immunosuppressive drug cyclosporin A, a CyPA ligand, did n ot inhibit CyPA-CR interaction. Our results established a new property of C yPA binding activity to CR. Since CR is a Ca2+-binding protein, CR-CyPA int eractions may be important in signaling pathways for induction of Ca2+-depe ndent cellular processes. (C) 1999 Elsevier Science B.V. All rights reserve d.