SEARCH · PubMed Health

Results for “Tacrolimus Binding Protein 1A”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed2001

FKBP binding characteristics of cardiac microsomes from diverse vertebrates.

FK506 binding protein (FKBP) is a cytosolic receptor for the immunosuppressive drug FK-506. The common isoform, FKBP12, was found to be associated with the calcium release channel (ryanodine receptor 1) of different species of vertebrate skeletal muscle, whereas 12.6, a novel FKBP isoform was found to be associated with canine cardiac ryanodine receptor (ryanodine receptor 2). Until recently, canine cardiac sarcoplasmic reticulum was considered to be the prototype for studying heart RyR2 and its interactions with FKBP. In this study, cardiac microsomes were isolated from diverse vertebrates: human, rabbit, rat, mice, dog, chicken, frog, and fish and were analyzed for their ability to bind or exchange with FKBP isoforms 12 and 12.6. Our studies indicate that RyR2 from seven out of the eight animals contain both FKBP12 and 12.6. Dog is the exception. It can now be concluded that the association of FKBP isoforms with RyR2 is widely conserved in the hearts of different species of vertebrates.

Animals↗

PubMed2001

Ryanodine receptors/calcium release channels in heart failure and sudden cardiac death.

Calcium (Ca2+) ions are second messengers in signaling pathways in all types of cells. They regulate muscle contraction, electrical signals which determine the cardiac rhythm and cell growth pathways in the heart. In the past decade cDNA cloning has provided clues as to the molecular structure of the intracellular Ca2+ release channels (ryanodine receptors, RyR, and inositol 1,4,5-trisphosphate receptors, IP3R) on the sarcoplasmic and endoplasmic reticulum (SR/ER) and an understanding of how these molecules regulate Ca2+ homeostasis in the heart is beginning to emerge. The intracellular Ca2+ release channels form a distinct class of ion channels distinguished by their structure, size, and function. Both RyRs and IP3Rs have gigantic cytoplasmic domains that serve as scaffolds for modulatory proteins that regulate the channel pore located in the carboxy terminal 10% of the channel sequence. The channels are tetramers comprised of four RyR or IP3R subunits. RyR2 is required for excitation-contraction (EC) coupling in the heart. Using co-sedimentation and co-immunoprecipitation we have defined a macromolecular complex comprised of RyR2, FKBP12.6, PKA, the protein phosphatases PP1 and PP2A, and an anchoring protein mAKAP. We have shown that protein kinase A (PKA) phosphorylation of RyR2 dissociates FKBP12.6 and regulates the channel open probability (P(o)). In failing human hearts RyR2 is PKA hyperphosphorylated resulting in defective channel function due to increased sensitivity to Ca2+-induced activation.

Animals↗

PubMed2006

Isolating the whole complex of target proteins of FK506 using affinity resins from novel solid phases.

The development of novel solid phases enabled us to create affinity resins that could be used to isolate the whole complex of target proteins responsible for the immunosuppressive effects of FK506 from rat brain lysate, whereas the affinity resins from commercially available matrices could not achieve this isolation. The results illustrate the enhanced effectiveness of the affinity resin made from this novel material at identifying the target protein of the bioactive compound compared to resins made from the well-known materials Affigel or Toyopearl. This effectiveness arises because the novel material is hydrophilic enough to reduce nonspecific binding proteins and because it has a higher density of ligands that capture the nonubiquitous target protein.

Animals↗

PubMed2006

The human FK506-binding proteins: characterization of human FKBP19.

Analysis of the human repertoire of the FK506-binding protein (FKBP) family of peptidyl-prolyl cis/trans isomerases has identified an expansion of genes that code for human FKBPs in the secretory pathway. There are distinct differences in tissue distribution and expression levels of each variant. In this article we describe the characterization of human FKBP19 (Entrez Gene ID: FKBP11), an FK506-binding protein predominantly expressed in vertebrate secretory tissues. The FKBP19 sequence comprises a cleavable N-terminal signal sequence followed by a putative peptidyl-prolyl cis/trans isomerase domain with homology to FKBP12. This domain binds FK506 weakly in vitro. FKBP19 mRNA is abundant in human pancreas and other secretory tissues and high levels of FKBP19 protein are detected in the acinar cells of mouse pancreas.

Amino Acid Sequence↗

PubMed2002

Wheat FKBP73 functions in vitro as a molecular chaperone independently of its peptidyl prolyl cis-trans isomerase activity.

Peptidyl-prolyl cis-trans isomerases (PPIases) catalyse protein folding by accelerating the slow step of cis-trans isomerisation of peptidyl-prolyl bonds. Wheat (Triticum aestivum L.) FKBP73 (wFKBP73) is a peptidyl-prolyl cis-trans isomerase belonging to the FK506-binding protein (FKBP) family. It comprises three FKBP12-like domains, tetratricopeptide repeats and a calmodulin-binding domain (CaMbd). In vitro studies indicated that wFKBP73 possesses PPIase activity, binds calmodulin and forms a heterocomplex with mammalian p23 and wheat Hsp90 in wheat-germ lysate. To further study the role of wFKBP73 we have analysed its chaperone properties. Using the thermal unfolding and aggregation of citrate synthase (CS) as a model system, we have shown that the plant wFKBP73 exhibits chaperone activity, being able to suppress CS aggregation independently of its PPIase activity. The wFKBP73 interacts transiently with non-native CS and slows down its inactivation kinetics, whereas the mammalian homologue, hFKBP52 binds tightly to CS and does not affect its rate of inactivation. Hence, the first plant FKBP shown to function as a molecular chaperone has a mode of action different from that of the mammalian FKBP52.

Calmodulin-Binding Proteins↗

PubMed2005

FKBP52.

The large molecular-weight immunophilin, FKBP52, is a known target of the immunosuppressive drug FK506. FKBP52 exhibits peptidyl-prolyl cis-trans isomerase (PPIase) activity, which is inhibited by the binding of FK506--properties that it shares with the smaller but better-studied immunophilin, FKBP12. Unlike FKBP12, however, FKBP52 does not mediate the immunosuppressive actions of FK506 and, due to its larger size, contains additional numerous functional domains. One such structure is a series of tetratricopeptide repeat (TPR) domains, which serve as binding sites for the ubiquitous and abundant molecular chaperone, Hsp90. It is this property as a TPR protein that best characterizes the known cellular roles of FKBP52. Here, we review the structural features of FKBP52 and relate them to the evolving and diverse functions of this protein. Although the most recognized role of FKBP52 is in regulation of steroid receptor signaling, other less well-known functions are also discussed.

Animals↗

PubMed2006

A rapid, reversible, and tunable method to regulate protein function in living cells using synthetic small molecules.

Rapid and reversible methods for perturbing the function of specific proteins are desirable tools for probing complex biological systems. We have developed a general technique to regulate the stability of specific proteins in mammalian cells using cell-permeable, synthetic molecules. We engineered mutants of the human FKBP12 protein that are rapidly and constitutively degraded when expressed in mammalian cells, and this instability is conferred to other proteins fused to these destabilizing domains. Addition of a synthetic ligand that binds to the destabilizing domains shields them from degradation, allowing fused proteins to perform their cellular functions. Genetic fusion of the destabilizing domain to a gene of interest ensures specificity, and the attendant small-molecule control confers speed, reversibility, and dose-dependence to this method. This general strategy for regulating protein stability should enable conditional perturbation of specific proteins with unprecedented control in a variety of experimental settings.

Animals↗

PubMed2006

Targeting protein stability with a small molecule.

Both genetic approaches and small-molecule inhibitors can be used to perturb protein function. Banaszynski et al. (2006) now describe a strategy to regulate the stability of a target protein, in which specificity is provided by a genetically encoded tag and temporal control is imparted by a small molecule.

Animals↗

PubMed2005

Genomic organization, chromosomal localization, and promoter of human gene for FK506-binding protein 12.6.

Cyclic ADP-ribose (cADPR) induces the release of Ca2+ from microsomes of pancreatic islets for insulin secretion. It has been demonstrated that cADPR binds to FK506-binding protein 12.6 (FKBP 12.6) on rat islet ryanodine receptor and that the binding of cADPR to FKBP12.6 frees the ryanodine receptor from FKBP12.6, causing it to release Ca2+ [Noguchi, N., Takasawa, S., Nata, K., Tohgo, A., Kato, I., Ikehata, F., Yonekura, H., Okamoto, H., 1997. Cyclic ADP-ribose binds to FK506-binding protein to release Ca2+ from islet microsomes. J. Biol. Chem. 272, 3133-3136.]. In this study, we cloned, characterized the structural organization of the human FKBP12.6, which is highly homologous to human FKBP12, and analyzed the promoters for FKBP12.6 and FKBP12. Human FKBP12.6 gene spanned about 16 kb in length and consisted of four exons and three introns. The positions of exon-intron junction of the FKBP12.6 gene were perfectly matched with those of FKBP12 gene except that FKBP12 has an additional exon, exon V, to code exclusively for 3'-UTR. Fluorescence in situ hybridization revealed that the FKBP12.6 gene was located on chromosome 2 p21-23, which is different from the locus (chromosome 20 p13) of the FKBP12 gene. Reporter gene analyses revealed that the regions of -58 approximately -24 of FKBP12.6 and -106 approximately -79 of FKBP12 are important for promoter activities. The promoters contain a consensus transcription factor binding sequence for Sp family in FKBP12.6 and Ets-1 in FKBP12. Electrophoretic mobility shift assays showed that nuclear proteins bind to the promoters. The DNA/protein complex on FKBP12.6 promoter was competed out by Sp1 consensus probe and the complex was supershifted by anti-Sp3 antibodies. On the other hand, the DNA/protein complex on FKBP12 promoter was competed out by Ets-1 consensus probe but not by its mutant probe, indicating that Sp3 and Ets-1 play an essential role in transcription of FKBP12.6 and FKBP12, respectively.

3' Untranslated Regions↗

PubMed2006

A kinetically trapped intermediate of FK506 binding protein forms in vitro: chaperone machinery dominates protein folding in vivo.

We have characterised the stability, binding and enzymatic properties of three human FK506 binding proteins (FKBP-12) differing only by the length and sequence of their N-terminus. One construct has a short hexa-his tag (6H-FKBP12); the second longer fusion protein (6HL-FKBP12) contains an additional thrombin protease cleavage site; the third has the long fusion tag removed and is essentially native FKBP-12 (cFKBP12). The proteins were purified both under native conditions and also using a refolding protocol. All three natively purified proteins have, within experimental error, the same peptidyl-prolyl isomerase (PPIase) activity (k(cat)/K(m) approximately 1 x 10(6)M(-1)s(-1)), and bind a natural inhibitor, rapamycin, with the same high affinity (K(d) approximately 6 nM). However, refolding of the protein containing the longer tag in vitro results in reduced PPIase activity (the k(cat)/K(m) was reduced from 1 x 10(6)M(-1)s(-1) to 0.81 x 10(6)M(-1)s(-1)) and a 6-fold affinity loss for rapamycin. Addition of both the long and short N-terminal his-tags slows the refolding kinetics of FKBP-12. However, the shorter his-tagged fusion protein regains fully native activity (> or =95%) while the longer regains only approximately 80-85% of native activity. Equilibrium urea denaturation titrations, isothermal titration calorimetry (ITC), analytical gel-filtration, and fluorescence binding data show that this loss of activity is not due to gross misfolding events, but is rather caused by the formation of a stable but subtly misfolded protein that has reduced peptidyl-prolyl isomerase (PPIase) activity and reduced affinity for rapamycin. The difference in behaviour between the in vitro refolded and native forms is due to the dominant role of the cellular chaperone/folding machinery.

Histidine↗

PubMed2002

Early decrease of the immunophilin FKBP 52 in the spinal cord of a transgenic model for amyotrophic lateral sclerosis.

Expressions of immunophilin FKBP-12 and FKBP-52 were examined in the spinal cord of transgenic mice with an ALS-linked mutant Cu/Zn superoxide dismutase (SOD1) gene. The immunoreactivity of FKBP-12 was present predominantly in the cytoplasm, but did not show a difference between age-matched wild type and transgenic (Tg) mice at 25 and 35 weeks. In contrast, the immunoreactivity of FKBP-52 was predominantly present in the nucleus, which progressively declined only in the Tg mice as early as an early presymptomatic stage at 25 weeks of age in the anterior horn neurons. The present result suggests that the downregulation of FKBP-52 may be involved in the pathogenesis in the early stages of amyotrophic lateral sclerosis (ALS).

Amyotrophic Lateral Sclerosis↗

PubMed2001

Mutation of FKBP associated protein 48 (FAP48) at proline 219 disrupts the interaction with FKBP12 and FKBP52.

Immunophilins are known as intracellular receptors for the immunosuppressant drugs, cyclosporin A, FK506, and rapamycin. They can be divided into two groups, cyclophilins that bind cyclosporin A and FK506 binding proteins (FKBPs) that bind FK506 and rapamycin. Many efforts were made to elucidate the physiological role of the immunophilins. Many of them are involved in intracellular signalling as they bind to calcium channels or to steroid receptor complexes. A yeast two-hybrid screen was used to identify further target proteins that interact with known proteins. Recently, a 48-kDa FKBP associated protein (FAP48) was isolated that binds to FKBP12 and FKBP52. Binding of FAP48 to FKBPs is inhibited by the macrolide FK506 indicating that the binding sites on the immunophilins coincide with the binding site for FK506. A peptidyl-prolyl motif on FAP48 should be responsible for the binding of the protein to FKBPs. We sequentially point mutated proline sites on FAP48 and checked the mutant proteins for interaction with FKBP12 and FKBP52. Mutation of proline 219 to alanine leads to a loss of interaction indicating that a cysteinyl prolyl site might be responsible for the binding of FAP48 to FKBPs. Thus we identified proline 219 being essential for the interaction.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Neuroprotective and antioxidant properties of FKBP-binding immunophilin ligands are independent on the FKBP12 pathway in human cells.

We focused on immunophilin isoforms in order to clarify the neuroimmunophilins which were identified as targets for the immunophilin ligands to elicit a neuroprotective effect. Although the expressions of five FK506-binding protein (FKBP) mRNAs were detected in both SH-SY5Y (human neuroblastoma) and U251 (human glioma) cell lysates, the FKBP12 mRNA expression was detected in only the SH-SY5Y cells, and not the U251 cells. However, we found that the SH-SY5Y and the U251 cells were equipotent in the intensity of cellular protection of FK506 (an immunosuppressive immunophilin ligand) and GPI1046 (a non-immunosuppressive FK506 analog), indicating that the protective effect and glutathione activation of FK506 and GPI1046 had little need to bind FKBP12. Therefore, we conclude that the neuroprotective and antioxidant properties of immunophilin ligands are independent on the FKBP12 pathway.

Actins↗

PubMed2003

Hippocampal CA1 neuron survival and cytosolic FKBP12, the 12 kDa FK506-binding protein, after ischemia and tacrolimus treatment in gerbils.

To assess the neuroprotective effect of tacrolimus (FK506) in transient forebrain ischemia models in gerbils, 10.0 mg/kg of FK506 was injected intraperitoneally immediately following reperfusion and at intervals of 1, 3, 6, 9, and 12 h after reperfusion. FK506 produced a significant neuroprotective effect for up to 6 h after 5 min of ischemia. Immunoblot and immunohistochemistry revealed that the amount of FKBP12, the 12-kDa FK506-binding protein, in the cytosol remained unchanged until 12 h after reperfusion. Translocation of FKBP12 from the nucleus to the cytosol was not observed until 24 h after reperfusion. Administration of FK506 did not appear to induce the cytosolic increase in FKBP12. In this study, no correlation was apparent between the post-ischemic therapeutic efficacy of FK506 and the post-ischemic changes in the cytosolic FKBP12.

Animals↗

PubMed2003

Gene expression of FK506-binding proteins 12.6 and 12 during chicken development.

FKBPs are cytosolic receptors for the immunosuppressive drug FK506. FKBP12.6 and FKBP12 associate with cardiac and skeletal muscle isoforms of ryanodine receptors and thereby regulate intracellular Ca(2+) release. The amino acid sequences of FKBP12.6 and FKBP12 are highly conserved among mammals and chicken. The expression profiles of FKBP12.6 and FKBP12 genes during chicken development were compared by Northern blot and in situ hybridization analyses. Transcripts of the FKBP12 gene were abundant throughout the embryo at early stages of development but subsequently underwent gradual down-regulation. Expression of the FKBP12.6 gene was mostly restricted to the heart during early embryogenesis and also underwent subsequent down-regulation, becoming localized to the atrium after hatching. Treatment of early embryos with FK506 had no apparent effect on embryogenesis. Retinoic acid induced marked abnormalities in cardiogenesis, but it did not affect FKBP gene expression. These results suggest that, even though FKBP12.6 and FKBP12 genes are expressed in chick embryos, FK506-sensitive functions of the encoded proteins do not appear to contribute to early embryogenesis or cardiogenesis.

Animals↗

PubMed2002

Inferring protein function from genomic sequence: Giardia lamblia expresses a phosphatidylinositol kinase-related kinase similar to yeast and mammalian TOR.

Functional assays of genes have historically led to insights about the activities of a protein or protein cascade. However, the rapid expansion of genomic and proteomic information for a variety of diverse taxa is an alternative and powerful means of predicting function by comparing the enzymes and metabolic pathways used by different organisms. As part of the Giardia lamblia genome sequencing project, we routinely survey the complement of predicted proteins and compare those found in this putatively early diverging eukaryote with those of prokaryotes and more recently evolved eukaryotic lineages. Such comparisons reveal the minimal composition of conserved metabolic pathways, suggest which proteins may have been acquired by lateral transfer, and, by their absence, hint at functions lost in the transition from a free-living to a parasitic lifestyle. Here, we describe the use of bioinformatic approaches to investigate the complement and conservation of proteins in Giardia involved in the regulation of translation. We compare an FK506 binding protein homologue and phosphatidylinositol kinase-related kinase present in Giardia to those found in other eukaryotes for which complete genomic sequence data are available. Our investigation of the Giardia genome suggests that PIK-related kinases are of ancient origin and are highly conserved.

Amino Acid Sequence↗

PubMed2006

Comparative analysis of calcineurin inhibition by complexes of immunosuppressive drugs with human FK506 binding proteins.

Multiple intracellular receptors of the FK506 binding protein (FKBP) family of peptidylprolyl cis/trans-isomerases are potential targets for the immunosuppressive drug FK506. Inhibition of the protein phosphatase calcineurin (CaN), which has been implicated in the FK506-mediated blockade of T cell proliferation, was shown to involve a gain of function in the FKBP12/FK506 complex. We studied the potential of six human FKBPs to contribute to CaN inhibition by comparative examination of inhibition constants of the respective FK506/FKBP complexes. Interestingly, these FKBPs form tight complexes with FK506, exhibiting comparable dissociation constants, but the resulting FK506/FKBP complexes differ greatly in their affinity for CaN, with IC50 values in the range of 0.047-17 microM. The different capacities of FK506/FKBP complexes to affect CaN activity are partially caused by substitutions corresponding to the amino acid side chains K34 and I90 of FKBP12. Only the FK506 complexes of FKBP12, FKBP12.6, and FKBP51 showed high affinity to CaN; small interfering RNA against these FKBP allowed defining the contribution of individual FKBP in an NFAT reporter gene assay. Our results allow quantitative correlation between FK506-mediated CaN effects and the abundance of the different FKBPs in the cell.

Amino Acid Sequence↗

PubMed2005

Characterization of the FKBP.rapamycin.FRB ternary complex.

Rapamycin is an important immunosuppressant, a possible anticancer therapeutic, and a widely used research tool. Essential to its various functions is its ability to bind simultaneously to two different proteins, FKBP and mTOR. Despite its widespread use, a thorough analysis of the interactions between FKBP, rapamycin, and the rapamycin-binding domain of mTOR, FRB, is lacking. To probe the affinities involved in the formation of the FKBP.rapamycin.FRB complex, we used fluorescence polarization, surface plasmon resonance, and NMR spectroscopy. Analysis of the data shows that rapamycin binds to FRB with moderate affinity (K(d) = 26 +/- 0.8 microM). The FKBP12.rapamycin complex, however, binds to FRB 2000-fold more tightly (K(d) = 12 +/- 0.8 nM) than rapamycin alone. No interaction between FKBP and FRB was detected in the absence of rapamycin. These studies suggest that rapamycin's ability to bind to FRB, and by extension to mTOR, in the absence of FKBP is of little consequence under physiological conditions. Furthermore, protein-protein interactions at the FKBP12-FRB interface play a role in the stability of the ternary complex.

Binding, Competitive↗