Peptidyl-prolyl cis-trans isomerase is the cyclosporin A-binding protein cyclophilin

Yeast cyclophilin: isolation and characterization of the protein, cDNA and gene

Cyclophilin (CPH) has been isolated from the yeast Saccharomyces cerevisiae, purified to homogeneity and partially sequenced. Oligodeoxyribonucleotides deduced from this sequence were used to isolate the corresponding cDNA and gene. An open reading frame coding for a 162-amino acid (aa) protein with a calculated Mr of 17,392, was deduced from the nucleotide sequence. Comparison between yeast and human CPH shows a very high overall sequence conservation (65% aa homology). The binding of yeast CPH to cyclosporin A is identical to that of human and bovine CPH. Unlike in Neurospora crassa, a mitochondrial form of CPH could not be detected in yeast. Southern-blot analysis of yeast DNA shows that only one CPH-related sequence is present per haploid genome, whereas at least 20 genes or pseudogenes were detected in the human and rat genome. Purified yeast CPH exhibits peptidyl-prolyl cis-trans isomerase activity, albeit to a far lesser extent than the mammalian protein.

A receptor for the immunosuppressant FK506 is a cis-trans peptidyl-prolyl isomerase

The structurally novel macrolide FK506 (refs 1,2) has recently been demonstrated to have potent immunosuppressive activity at concentrations several hundredfold lower than cyclosporin A (CsA). Cyclosporin A, a cyclic peptide, has found widespread clinical use in the prevention of graft rejection following bone marrow and organ transplantation. The mechanisms of immunosuppression mediated by FK506 and CsA appear to be remarkably similar, suggesting that these unrelated structures act on a common receptor or on similar molecular targets, perhaps the CsA receptor, cyclophilin, which has recently been shown by Fischer et al. and Takahashi et al. to have cis-trans peptidyl-prolyl isomerase activity. We have prepared an FK506 affinity matrix and purified a binding protein for FK506 from bovine thymus and from human spleen. This FK506-binding protein (FKBP) has a relative molecular mass (Mr) of approximately 14,000(14K), a pI of 8.8-8.9, and does not cross-react with antisera against cyclophilin. The first 40 N-terminal residues of the bovine and 16 residues of the human FKBP were determined; the 16-residue fragments are identical to each other and unrelated to any known sequences. This protein catalyses the cis-trans isomerization of the proline amide in a tetrapeptide substrate and FK506 inhibits the action of this new isomerase. The FKBP and cyclophilin appear to be members of an emerging class of novel proteins that regulate T cell activation and other metabolic processes, perhaps by the recognition (and possibly the isomerization) of proline-containing epitopes in target proteins.

A cytosolic binding protein for the immunosuppressant FK506 has peptidyl-prolyl isomerase activity but is distinct from cyclophilin

CYCLOSPORIN A and the newly discovered immunosuppressant, FK-506, are potent inhibitors of T cell activation. In addition to their clinical importance in the prevention of allograft rejection, cyclosporin A and FK-506 represent important reagents for the study of the molecular mechanisms of lymphocyte activation. Cyclosporin A, a cyclic undecapeptide and FK-506, a macrolide, although chemically distinct, inhibit similar lymphocyte activation responses. The earliest responses inhibited in the T cell seem to be the expression of early phase T cell-activation genes for interleukins 2, 3 and 4, granulocyte-macrophage colony stimulating factor and gamma interferon. Although FK-506 and cyclosporin A seem to inhibit similar signal transduction processes, they do so be interacting with distinct cytosolic proteins. We report here the purification to homogeneity of a specific FK-506 binding protein that is distinct from the cyclosporin A-binding protein, cyclophilin. In addition, we show that this FK-506 binding protein, like cyclophilin, has peptidyl-prolyl isomerase activity.

Structure and expression of the human motilin gene

The human motilin gene was isolated from a human genomic library and its structure was determined by restriction mapping and DNA sequence analysis. The gene consists of five exons separated by four introns spanning approximately 9 kb of genomic DNA. Exon I encodes the 5' untranslated portion of the motilin mRNA. Exons II and III encode the signal peptide and the 22-amino-acid motilin peptide; codons encoding the motilin moiety are split by an intron. The carboxy-terminal motilin-associated peptide (MAP) is largely encoded by Exons III and IV with the last two amino acids of the motilin precursor and the 3' untranslated region encoded by Exon V. Thus, the motilin gene has an unusual structure in which a small bioactive peptide is encoded on two distinct exons. Examination of the expression of the human and nonhuman primate motilin gene by Northern hybridization analysis indicates that it is expressed in a number of gastrointestinal and extragastrointestinal tissues.

Nucleotide sequences of fic and fic-1 genes involved in cell filamentation induced by cyclic AMP in Escherichia coli

The nucleotide sequences of fic-1 involved in the cell filamentation induced by cyclic AMP in Escherichia coli and its normal counterpart fic were analyzed. The open reading frame of both fic-1 and fic coded for 200 amino acids. The Gly at position 55 in the Fic protein was changed to Arg in the Fic-1 protein. The promoter activity of fic was confirmed by fusing fic and lacZ. The gene downstream from fic was found to be pabA (p-aminobenzoate). There is an open reading frame (ORF190) coding for 190 amino acids upstream from the fic gene. Computer-assisted analysis showed that Fic has sequence similarity with part of CDC28 of Saccharomyces cerevisiae, CDC2 of Schizosaccharomyces pombe, and FtsA of E. coli. In addition, ORF190 has sequence similarity with the cyclosporin A-binding protein cyclophilin.

Kinetic beta-deuterium isotope effects suggest a covalent mechanism for the protein folding enzyme peptidylprolyl cis/trans-isomerase

The cis/trans interconversion of Glt-Ala-Ala-Pro-Phe-4-nitroanilide and Glt-Ala-Gly-Pro-Phe-4-nitroanilide was studied both enzymatically and nonenzymatically by measuring kinetic beta-deuterium isotope effects. The hydrogen atom at the alpha-carbon atom of the Xaa residue within the Xaa-Pro moiety was substituted by deuterium. In the nonenzymatic case the transition state of rotation is reflected by kH/kD greater than 1. When catalysed by 17 kDa PPIase the same bond rotation is characterized by kH/kD less than 1. This suggests a covalent mechanism of catalysis which involves an approximately tetravalent carbon of the prolyl imidic bond for the transition state of reaction.

Drosophila ninaA gene encodes an eye-specific cyclophilin (cyclosporine A binding protein)

Mutations in the ninaA gene of Drosophila severely reduce the amount of rhodopsin specifically in R1-6 photoreceptors. Isolation of the ninaA gene by chromosomal walking revealed that it is expressed only in the eye and encodes a 237-amino acid polypeptide that shows strong sequence similarity to cyclophilin, a putative molecular target for cyclosporine A, a potent immunosuppressant used in human organ transplantations. Unlike most cyclophilins characterized to date, the ninaA-encoded protein has a putative signal sequence and a transmembrane domain. Each of the three ehtyl methanesulfonate-induced ninaA mutant alleles analyzed shows a single nucleotide change in the mRNA coding region leading to either a nonsense or a missense mutation. We find no evidence that the ninaA-encoded protein is directly involved in phototransduction. The only detectable mutant phenotype that correlates with the severity of molecular defects in the three mutants is the amount of depletion of R1-6 rhodopsin. The above results and the recent findings that cyclophilin is a peptidylprolyl cis-trans-isomerase suggest that the ninaA-encoded protein may be required for proper folding and stability of R1-6 rhodopsin.

NGF induction of the gene encoding the protease transin accompanies neuronal differentiation in PC12 cells

Various proteases have been found to be released by the growth cones of developing neurons in culture and have been hypothesized to play a role in the process of axon elongation. We report here that nerve growth factor (NGF) induced the gene encoding the metalloprotease transin in PC12 cells with a time course coincident with the initial appearance of neurites by these cells. Acidic and basic fibroblast growth factors also stimulated transin mRNA expression and neurite outgrowth, whereas various other agents had no effects on either of these phenomena. In contrast, dexamethasone was found to inhibit the induction of transin mRNA when added with, or following, NGF treatment. Finally, we show that sequences contained within 750 bp of the 5' untranscribed region of the transin gene confer responsiveness to NGF and dexamethasone.

The ninaA gene required for visual transduction in Drosophila encodes a homologue of cyclosporin A-binding protein

Mutations of the Drosophila melanogaster ninaA gene affect phototransduction: ninaA mutant flies have a 10-fold reduction in the levels of rhodopsin in the R1-R6 photoreceptor cells. The ninaA gene was isolated and found to encode a 237-amino-acid protein that has over 40% amino-acid sequence identity with the vertebrate cyclosporin A-binding protein, cyclophilin, a protein that seems to be involved in T-lymphocyte activation. The remarkable evolutionary conservation of cyclophilin in two phylogenetically distant organisms and its involvement in diverse transduction processes suggests that this protein plays an important role in cellular metabolism. Indeed, cyclophilin has recently been shown to be a prolyl cis-trans isomerase that catalyses, in vitro, rate-limiting steps in the folding of a number of proteins. Here, we present evidence for the involvement of cyclophilin-like molecules in a defined cellular process. The availability of mutations in a cyclophilin gene provides a new model system for the study of cyclophilin and cyclosporin action.