title: An endoplasmic reticulum-specific cyclophilin.
abstract: Cyclophilin is a ubiquitously expressed cytosolic peptidyl-prolyl cis-trans isomerase that is inhibited by the immunosuppressive drug cyclosporin A. A degenerate oligonucleotide based on a conserved cyclophilin sequence was used to isolate cDNA clones representing a ubiquitously expressed mRNA from mice and humans. This mRNA encodes a novel 20-kDa protein, CPH2, that shares 64% sequence identity with cyclophilin. Bacterially expressed CPH2 binds cyclosporin A and is a cyclosporin A-inhibitable peptidyl-prolyl cis-trans isomerase. Cell fractionation of rat liver followed by Western blot (immunoblot) analysis indicated that CPH2 is not cytosolic but rather is located exclusively in the endoplasmic reticulum. These results suggest that cyclosporin A mediates its effect on cells through more than one cyclophilin and that cyclosporin A-induced misfolding of T-cell membrane proteins normally mediated by CPH2 plays a role in immunosuppression.
authors.affiliation: Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
authors.forename: K W
authors.initials: KW
authors.lastname: Hasel
authors.forename: J R
authors.initials: JR
authors.lastname: Glass
authors.forename: M
authors.initials: M
authors.lastname: Godbout
authors.forename: J G
authors.initials: JG
authors.lastname: Sutcliffe
mesh_terms: D000591:Amino Acid Isomerases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D003524:Cyclosporins / Q000378:metabolism; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D004721:Endoplasmic Reticulum / Q000502:physiology*; D015723:Gene Library; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D015345:Oligonucleotide Probes; D019696:Peptidylprolyl Isomerase; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics / Q000302:isolation & purification; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D013950:Thymus Gland / Q000502:physiology
chemical_list: D002352:Carrier Proteins; D003524:Cyclosporins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D011994:Recombinant Proteins; D012313:RNA; D004247:DNA; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase