Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The immunosuppressants cyclosporin A, FK506, and rapamycin inhibit growth of unicellular eukaryotic microorganisms and also block activation of T lymphocytes from multicellular eukaryotes. In vitro, these compounds bind and inhibit two different types of peptidyl-prolyl cis-trans isomerases. Cyclosporin A binds cyclophilins, whereas FK506 and rapamycin bind FK506-binding proteins (FKBPs). Cyclophilins and FKBPs are ubiquitous, abundant, and targeted to multiple cellular compartments, and they may fold proteins in vivo. Previously, a 12-kDa cytoplasmic FKBP was shown to be only one of at least two FK506-sensitive targets in the yeast Saccharomyces cerevisiae. We find that a second FK506-sensitive target is required for amino acid import. Amino acid-auxotrophic yeast strains (trp1 his4 leu2) are FK506 sensitive, whereas prototrophic strains (TRP1 his4 leu2, trp1 HIS4 leu2, and trp1 his4 LEU2) are FK506 resistant. Amino acids added exogenously to the growth medium mitigate FK506 toxicity. FK506 induces GCN4 expression, which is normally induced by amino acid starvation. FK506 inhibits transport of tryptophan, histidine, and leucine into yeast cells. Lastly, several genes encoding proteins involved in amino acid import or biosynthesis confer FK506 resistance. These findings demonstrate that FK506 inhibits amino acid import in yeast cells, most likely by inhibiting amino acid transporters. Amino acid transporters are integral membrane proteins which import extracellular amino acids and constitute a protein family sharing 30 to 35% identity, including eight invariant prolines. Thus, the second FK506-sensitive target in yeast cells may be a proline isomerase that plays a role in folding amino acid transporters during transit through the secretory pathway.
Mol Cell Biol 1993 Aug
PMID:The immunosuppressant FK506 inhibits amino acid import in Saccharomyces cerevisiae. 768 45

In their unliganded state, mouse glucocorticoid receptors (GR) that are overexpressed in the WCL2 line of Chinese hamster ovary cells are distributed in a nonrandom manner throughout all planes of the nucleus. These untransformed nuclear receptors exist in a heterocomplex containing three heat shock proteins, hsp90, hsp70, and hsp56, the latter being an immunophilin of the FK506 binding type whose cellular function is unknown. Because a knowledge of the cellular distribution of hsp56 could provide important clues to its function in steroid-receptor heterocomplexes, we have examined hsp56 localization in intact cells by indirect immunofluorescence using the UPJ56 antibody. The majority of hsp56 is located in the nucleus, with substantial amounts also visualized in the cytoplasm of intact cells. The cytoplasmic hsp56 was examined in rat pulmonary endothelial cells where the protein was found to colocalize with microtubules. The nuclear hsp56 was examined in the WCL2 cells, where the protein was found by confocal imaging to colocalize throughout all planes of the nucleus in the same mottled pattern as the overexpressed GR. Like the GR, the nuclear hsp56 is recovered largely in the cytosolic fraction after hypotonic rupture of WCL2 cells. An observation potentially related to the microtubule-associated fraction of hsp56 is that immunoadsorption of hsp56 from WCL2 cytosol is accompanied by coadsorption of the microtubule-associated protein-1C complex. These observations are discussed with respect to the possible biological functions of hsp56 in the folding and/or cytoplasmic-nuclear trafficking of the receptor.
Mol Endocrinol 1994 Dec
PMID:The hsp56 immunophilin component of untransformed steroid receptor complexes is localized both to microtubules in the cytoplasm and to the same nonrandom regions within the nucleus as the steroid receptor. 770 60

The folding pathways of multi-domain proteins are still poorly understood due to the complexity of the reaction involving domain folding, association and, in many cases, prolyl cis/trans isomerization. Here, we have established a kinetic model for the folding of the Fab fragment of the antibody MAK 33 with intact disulfide bonds. Folding of the hetero-dimeric protein from the completely denatured, oxidized state comprises the pairwise association of the two domains of each chain with those of the partner protein. Both the reactivation of the Fab fragment in which the two constituent polypeptide chains were covalently linked via a cystine bond (Fab) and that of a mutant lacking this covalent linkage (Fab/-cys) were monitored by ELISA. Folding of the Fab fragment is a slow process, which can be described by a single exponential term. The kinetic phase reflects a folding step after the association of the two chains. The same reaction was detected in the folding of Fab/-cys but an additional rate-limiting step is involved that is due to a unimolecular step in the folding of the isolated light chain. This implies that, during Fab reactivation, Fd associates with the light chain at the stage of an earlier folding intermediate, thus eliminating the additional slow folding step of the light chain observed with Fab/-cys. Both in Fab and Fab/-cys renaturation, the folding reaction after association is determined by prolyl isomerization. Therefore, at least four different association-competent folding intermediates have to be postulated according to the folding stage of light chain and the configuration of at least one prolyl-peptide bond. Using the different substrate specificities of cyclophilin and FK506 binding protein, we have obtained evidence that Pro159 within the Fd fragment may be responsible for the observed slow folding phase after association, although three other proline residues adopt a cis configuration in the native protein. Furthermore, the data suggest that in the case of the Fab fragment, association is a prerequisite for cis/trans isomerization of prolyl peptide bonds, implying that the quaternary but not the tertiary structure determines the cis-configuration of the prolyl residue in Fd involved in the rate-limiting folding reaction.
J Mol Biol 1995 Apr 21
PMID:Association of antibody chains at different stages of folding: prolyl isomerization occurs after formation of quaternary structure. 773 Oct 44

The immunophilin family of FK506-binding proteins (FKBPs), involved in eukaryotic protein-folding and cell regulation, have recently been found to have prokaryotic homologues. Genes with sequences homologous to those encoding human FKBPs were examined in Neisseria species. An FKBP DNA sequence was present, as shown by the polymerase chain reaction and Southern blotting experiments, in the chromosome of Neisseria meningitidis (14 strains) and in all 11 different commensal Neisseria spp. studied, but was not found in Neisseria gonorrhoeae (11 strains tested) or in Moraxella catarrhalis. The nucleotide and predicted protein sequences of the FKBP-encoding domain from five of the meningococcal strains were highly conserved (e.g. > or = 97% homologous). The meningococcal nucleotide sequence was > or = 93% homologous and the consensus meningococcal protein sequence was > or = 97% homologous to FKBP sequences found in seven different commensal Neisseria spp. The meningococcal nucleotide and predicted protein sequences were > or = 59% homologous to the conserved C-terminus of the human FKBP gene family. The FKBP nucleotide sequence was present as a single copy in the chromosome of commensal Neisseria spp. and in most strains of N. meningitidis. The FKBP gene was linked to the silent pilin locus, pilS, in class II-piliated meningococcal strains. In meningococcal strains expressing class I pili, the FKBP gene was linked to one of several pilS loci but not the pilE locus present in these strains. FKBP genes found in commensal Neisseria spp. were not linked to known pilin loci.
Mol Microbiol 1993 Oct
PMID:Analysis in Neisseria meningitidis and other Neisseria species of genes homologous to the FKBP immunophilin family. 796 9

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-2 (IL-2) are produced by stimulation with phorbol-12-myristate acetate (PMA) and calcium ionophore (A23187) in human T cell leukemia Jurkat cells. The expression of GM-CSF and IL-2 is inhibited by immunosuppressive drugs such as cyclosporin A (CsA) and FK506. Earlier studies on the IL-2 gene expression showed that overexpression of calcineurin (CN), a Ca2+/calmodulin-dependent protein phosphatase, can stimulate transcription from the IL-2 promoter through the NF-AT-binding site. In this study, we obtained evidence that transfection of the cDNAs for CN A (catalytic) and CN B (regulatory) subunits also augments transcription from the GM-CSF promoter and recovers the transcription inhibited by CsA. The constitutively active type of the CN A subunit, which lacks the auto-inhibitory and calmodulin-binding domains, acts in synergy with PMA to activate transcription from the GM-CSF promoter. We also found that the active CN partially replaces calcium ionophore in synergy with PMA to induce expression of endogenous GM-CSF and IL-2. By multimerizing the regulatory elements of the GM-CSF promoter, we found that one of the target sites for the CN action is the conserved lymphokine element 0 (CLE0), located at positions between -54 and -40. Mobility shift assays showed that the CLE0 sequence has an AP1-binding site and is associated with an NF-AT-like factor, termed NF-CLE0 gamma. NF-CLE0 gamma binding is induced by PMA/A23187 and is inhibited by treatment with CsA. These results suggest that CN is involved in the coordinated induction of the GM-CSF and IL-2 genes and that the CLE0 sequence of the GM-CSF gene is a functional analogue of the NF-AT-binding site in the IL-2 promoter, which mediates signals downstream of T cell activation.
Mol Biol Cell 1994 Jan
PMID:Calcineurin potentiates activation of the granulocyte-macrophage colony-stimulating factor gene in T cells: involvement of the conserved lymphokine element 0. 818 61

We have previously shown that a human B lymphoma cell line, B104, expressed surface IgM (sIgM) and surface IgD (sIgD), and that crosslinking of sIgM and sIgD by anti-IgM antibody (Ab) and anti-IgD Ab, respectively, induced Ca2+ influx to almost the same degree, whereas only sIgM-crosslinking caused B104 cell death. Here, we investigated the accumulation of cyclic AMP (cAMP), the hydrolysis of inositol phosphates, protein kinase C (PKC) activity and the induction of Egr-1 and c-fos mRNA expression by sIgM- and sIgD-crosslinking to examine differences in the signals mediated through sIgM and sIgD in B104 cells. Both sIgM- and sIgD-crosslinking with antibodies induced elevation of cAMP levels, phosphatidylinositol turnover, PKC activation and expression of Egr-1 and c-fos mRNA, although sIgM-crosslinking was more effective than sIgD-crosslinking, presumably due to the higher expression of sIgM than of sIgD. Egr-1 mRNA expression induced by sIgM- and sIgD-crosslinking was inhibited by H7, erbstatin and genistein, but not by HA1004. Erbstatin and genistein inhibited the sIg-crosslinking-induced Egr-1 mRNA expression in a dose-dependent manner parallel to that observed in the inhibition of sIg-crosslinking-induced protein tyrosine phosphorylation. Phorbol myristate acetate induced Egr-1 mRNA expression but forskolin and dibutyryl cyclic AMP did not. These findings suggest that the Egr-1 mRNA activating signals through sIgM and sIgD are protein tyrosine kinase- and PKC-dependent, but protein kinase A-independent. Cyclosporin A (CsA) and FK506 rescued B104 cells from death induced by anti-IgM Ab, but did not affect the expression of Egr-1 and c-fos mRNA, showing that CsA and FK506 affect signal transducers differently from or downstream to these molecules. The difference in signals transduced through sIgM and sIgD in B104 cells is discussed.
Mol Immunol 1994 Jan
PMID:Induction of phosphatidylinositol turnover and EGR-1 mRNA expression by crosslinking of surface IgM and IgD in the human B cell line B104. 830 96

CD28 is a 44 kDa Ig superfamily cell surface molecule expressed on most mature T cells. Through its interaction with the recently identified B7/BB1 counter-receptor, it is believed to play an important role as a co-stimulator of T cells along with the TCR-CD3 complex. Activation of T cells with CD28 mAbs synergizes with TCR-CD3 and CD2 stimulation, resulting in long term T cell proliferation, differentiation of cytotoxic T cells and production of large amounts of cytokines. In order to further delineate the role of CD28 in signal transduction and T cell activation, human CD28 was transfected into CD3+ murine T cell hybridomas. High levels of cell surface CD28 expression was achieved by protoplast fusion. The transfected molecule retained all the native CD28 mAb epitopes found on human T cells. In these transfectants, CD28 mAbs, similarly to CD3 mAbs, were able to induce Ca2+ mobilization, IL-2 promoter induction (measured as beta-galactosidase activity in T cells hybridomas pre-transfected with the IL-2-lac Z reporter gene), IL-2 secretion, TNF alpha production and apoptosis (observed as growth arrest and genome fragmentation). The parental host cells, or cells transfected with vector alone, responded only to mAbs to CD3. IL-2 secretion in the transfectants was obtained using either an IgM mAb to CD28 or IgG mAbs presented on the surface of IgG-FcR+ B lymphoma cells. Optimal activation via CD28 was inhibited by suboptimal concentrations of soluble CD3 mAb, suggesting an interaction between the two pathways. The immunosuppressive drugs Cyclosporin A and FK506 completely blocked CD28 and CD3 mediated IL-2 production in these transfectants whereas rapamycin had only a partial inhibitory effect. Finally, since the transfected human CD28 molecule confers full functional responsiveness to the murine T cell hybridomas without the need for costimulators such as PMA, this model is ideal for studying the structure-function relationships of the CD28 molecule as well as the transmembrane and cytoplasmic associations implied in CD28 signaling.
Mol Immunol 1994 Jan
PMID:Functional expression of human CD28 in murine T cell hybridomas. 830 98

A novel method, which we call GenStar, has been developed to suggest chemically reasonable structures which fill the active sites of enzymes. The proposed molecules provide good steric contact with the enzyme and exist in low-energy conformations. These structures are composed entirely of sp3 carbons which are grown sequentially, but which can also branch or form rings. User-selected enzyme seed atoms may be used to determine the area in which structure generation begins. Alternatively, GenStar may begin with a predocked 'inhibitor core' from which atoms are grown. For each new atom generated by the program, several hundred candidate positions representing a range of reasonable bond lengths, bond angles, and torsion angles are considered. Each of these candidates is scored, based on a simple enzyme contact model. The selected position is chosen at random from among the highest scoring cases. Duplicate structures may be removed using a variety of criteria. The compounds may be energy minimized and displayed using standard modeling programs. Also, it is possible to analyze the collection of all structures created by GenStar and locate binding motifs for common fragments such as benzene and naphthylene. Tests of the method using HIV protease, FK506 binding protein (FKBP-12) and human carbonic anhydrase (HCA-II) demonstrated that structures similar to known potent inhibitors may be generated with GenStar.
J Comput Aided Mol Des 1993 Feb
PMID:GenStar: a method for de novo drug design. 847 16

The FK506-binding immunophilin hsp56 (FKBP52) is one of several chaperone proteins associated with untrasformed steroid receptors in a multiprotein heterocomplex. The function of heat shock protein 56 (hsp56) with respect to receptor action is unknown. hsp56 is not required for glucocorticoid receptor heterocomplex assembly or for proper folding of the receptor hormone-binding domain into a high affinity steroid-binding conformation. In intact cells, the majority of the hsp56 is located in the nucleus, with a minority colocalizing with microtubules in the cytoplasm. hsp56 contains a conserved negatively charged domain that we speculate might serve as a nuclear localization signal recognition sequence. Here we show that injection of an antibody raised against this negative sequence into intact L cells impedes subsequent dexamethasone-mediated shift of the glucocorticoid receptor into the nucleus. Nonimmune rabbit serum and an antibody raised against another site on hsp56 do not affect receptor movement. Inhibition of receptor movement by the 419 antibody against the negative sequence is blocked by preincubation with purified hsp56, but not by preincubation with purified hsp90, hsp70, or BSA. These observations are consistent with the possibility that hsp56 is involved in receptor trafficking to the nucleus, possibly functioning as the nuclear localization signal recognition protein. Receptor trafficking to the nucleus is not affected by FK506, indicating that the peptidylprolyl isomerase activity of hsp56 is not involved.
Mol Endocrinol 1995 Nov
PMID:Evidence that the FK506-binding immunophilin heat shock protein 56 is required for trafficking of the glucocorticoid receptor from the cytoplasm to the nucleus. 858 32

The PMC1 gene in Saccharomyces cerevisiae encodes a vacuolar Ca2+ ATPase required for growth in high-Ca2+ conditions. Previous work showed that Ca2+ tolerance can be restored to pmc1 mutants by inactivation of calcineurin, a Ca2+/calmodulin-dependent protein phosphatase sensitive to the immunosuppressive drug FK506. We now report that calcineurin decreases Ca2+ tolerance of pmc1 mutants by inhibiting the function of VCX1, which encodes a vacuolar H+/Ca2+ exchanger related to vertebrate Na+/Ca2+ exchangers. The contribution of VCX1 in Ca2+ tolerance is low in strains with a functional calcineurin and is high in strains which lack calcineurin activity. In contrast, the contribution of PMC1 to Ca2+ tolerance is augmented by calcineurin activation. Consistent with these positive and negative roles of calcineurin, expression of a vcx1::lacZ reporter was slightly diminished and a pmc1::lacZ reporter was induced up to 500-fold by processes dependent on calcineurin, calmodulin, and Ca2+. It is likely that calcineurin inhibits VCX1 function mainly by posttranslational mechanisms. Activities of VCX1 and PMC1 help to control cytosolic free Ca2+ concentrations because their function can decrease pmc1::lacZ induction by calcineurin. Additional studies with reporter genes and mutants indicate that PMR1 and PMR2A, encoding P-type ion pumps required for Mn2+ and Na+ tolerance, may also be induced physiologically in response to high-Mn2+ and -Na+ conditions through calcineurin-dependent mechanisms. In these situations, inhibition of VCX1 function may be important for the production of Ca2+ signals. We propose that elevated cytosolic free Ca2+ concentrations, calmodulin, and calcineurin regulate at least four ion transporters in S. cerevisiae in response to several environmental conditions.
Mol Cell Biol 1996 May
PMID:Calcineurin inhibits VCX1-dependent H+/Ca2+ exchange and induces Ca2+ ATPases in Saccharomyces cerevisiae. 862 89


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