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

BIOINFORMATICS, TISSUE DISTRIBUTION, AND SUBCELLULAR LOCALIZATION ANALYSES OF FK506 BINDING PROTEIN 12B FROM SILKWORMS

FK506 binding proteins (FKBPs) are intracellular receptors of the immunosuppressant FK506 and play important roles in the correct folding of new proteins and the self-assembly of biological macromolecules. FKBP12 is a member of the FKBP family that is widely expressed and highly conserved in many species. In this study, we identified the complete cDNA sequence encoding the FKBP12 ortholog in Bombyx mori, named Bm-FKBP12B (GenBank accession no. DQ443423). Multiple-sequence alignment among different species revealed a high similarity among FKBP12 paralogs and orthologs. Bioinformatics analysis of the Bm-FKBP12B gene showed that it is located on chromosome 20 and consists of three exons and two introns. We cloned, expressed, and purified the Bm-FKBP12B protein in Escherichia coli and generated a specific polyclonal antibody against Bm-FKBP12B. The real-time quantitative reverse-transcription (qRT) PCR and Western blotting results showed that Bm-FKBP12B was present throughout all of the development stages, but it was abundant in the adult and embryo stages. Bm-FKBP12B expression was higher in the silk gland and gut, suggesting that it might play important roles in regulating gene expression in the silk gland and during silk fiber formation. Bm-FKBP12B protein was distributed in the cytoplasm, nucleus, and nuclear membrane.

Conditional transgenesis using Dimerizable Cre (DiCre)

Cre recombinase is extensively used to engineer the genome of experimental animals. However, its usefulness is still limited by the lack of an efficient temporal control over its activity. We have recently developed a conceptually new approach to regulate Cre recombinase, that we have called Dimerizable Cre or DiCre. It is based on splitting Cre into two inactive moieties and fusing them to FKBP12 (FK506-binding protein) and FRB (binding domain of the FKBP12-rapamycin associated protein), respectively. These latter can be efficiently hetero-dimerized by rapamycin, leading to the reinstatement of Cre activity. We have been able to show, using in vitro approaches, that this ligand-induced dimerization is an efficient way to regulate Cre activity, and presents a low background activity together with a high efficiency of recombination following dimerization. To test the in vivo performance of this system, we have, in the present work, knocked-in DiCre into the Rosa26 locus of mice. To evaluate the performance of the DiCre system, mice have been mated with indicator mice (Z/EG or R26R) and Cre-induced recombination was examined following activation of DiCre by rapamycin during embryonic development or after birth of progenies. No recombination could be observed in the absence of treatment of the animals, indicating a lack of background activity of DiCre in the absence of rapamycin. Postnatal rapamycin treatment (one to five daily injection, 10 mg/kg i.p) induced recombination in a number of different tissues of progenies such as liver, heart, kidney, muscle, etc. On the other hand, recombination was at a very low level following in utero treatment of DiCrexR26R mice. In conclusion, DiCre has indeed the potentiality to be used to establish conditional Cre-deleter mice. An added advantage of this system is that, contrary to other modulatable Cre systems, it offers the possibility of obtaining regulated recombination in a combinatorial manner, i.e. induce recombination at any desired time-point specifically in cells characterized by the simultaneous expression of two different promoters.

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.

CYCLOSPORINE A MEDIATES FIBROPROLIFERATION THROUGH EPITHELIAL CELLS

BACKGROUND

Obliterative bronchiolitis (OB) is the major cause of morbidity and mortality after lung transplantation. The potential role of immunosuppressive drugs in the development of OB is uncertain, but there are limited data indicating that cyclosporine A (CsA) may have a direct fibrogenic effect on various human cell types. Epithelium-fibroblast interactions have been suggested to play a crucial role in the course of fibroproliferation, which is a major feature of OB.

METHODS

We studied the effect of CsA and FK506 on primary human lung fibroblast proliferation in a human epithelial-fibroblast interactive model.

RESULTS

Clinically relevant concentrations of CsA (0.1-1 microg/mL) and FK506 (0.001-0.01 microg/mL) did not affect fibroblast proliferation in monocultures. Conditioned medium (CM) from untreated epithelial cells (Calu-3) stimulated fibroblast proliferation. CM from FK506-treated (0.001-0.1 microg/mL) epithelial cells had no significant additive effect on fibroblast proliferation compared with CM of untreated epithelial cells. In contrast, CM obtained from epithelial cells treated with 0.1 microg/mL CsA significantly enhanced fibroblast proliferation compared with CM of untreated epithelial cells. This proliferative effect of 0.1 microg/mL CsA was mediated by epithelial-derived factors greater than 100 kDa.

CONCLUSIONS

These data demonstrate that a clinically relevant concentration of CsA stimulates fibroblast proliferation through mediators produced by airway epithelial cells, raising the possibility that CsA may contribute to the development of OB after lung transplantation.