Immunophilins interact with calcineurin in the absence of exogenous immunosuppressive ligands.

Cárdenas, María E.; Hemenway, Charles S.; Muir, R S; Ye, R; Fiorentino, David; Heitman, Joseph

doi:10.1002/j.1460-2075.1994.tb06940.x

Cited by 149 publications

(174 citation statements)

References 81 publications

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“…It has been reported that in the absence of exogenous ligand, FKBP12 interacts with and modulates calcineurin activity, and that the immunosuppressant FK506 enhances preexisting immunophilin-calcineurin complexes (36). In this context, we can imagine that FAP48 could interfere in the formation of the complex between calcineurin and FKBP12 to prevent their association, thus leading to an optimum immune response of T cells.…”

Section: Discussionmentioning

confidence: 99%

The FKBP-associated protein FAP48 is an antiproliferative molecule and a player in T cell activation that increases IL2 synthesis

Krummrei

Baulieu

Chambraud

2003

Proc. Natl. Acad. Sci. U.S.A.

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FAP48 was identified and cloned thanks to its interaction with FK506-binding proteins (FKBPs) such as FKBP52 and FKBP12, which belong to the large family of immunophilins that bind the macrolide immunosuppressant drugs FK506 and rapamycin. We have previously shown that FAP48 -FKBP complexes are dissociated by FK506 and rapamycin, suggesting that FAP48 is an endogenous ligand of FKBP. The present work describes the biochemical consequences of FAP48 overexpression, induced by the tetracycline analogue doxycycline, in an established cell line derived from Jurkat T cells. We report that overexpression of FAP48 results in the inhibition of cellular proliferation as does the exposure of Jurkat T cells to FK506. We also show that the expression levels of argininosuccinate synthetase and the Myc antagonist Mxi1 are modified by overexpression of FAP48, suggesting that these proteins could be good candidates to mediate the antiproliferative effect of FAP48. FAP48 affects neither the calcineurin-dependent nuclear factor of activated T cells (NFAT)1 nor JNK͞p38-dependent pathways that mediate immunosuppression by FK506. However, contrary to FK506, which blocks IL2 synthesis, we observed that FAP48 -FKBP complexes increase IL2 production, thus revealing a previously uncharacterized aspect of the immunosuppressive mechanism of FK506.T he pharmacological actions of immunosuppressant drugs such as FK506 and rapamycin are mediated in the cell by intracellular proteins named FK506-binding proteins (FKBPs) belonging to the immunophilin family (reviewed in refs. 1-3).The main cytoplasmic FKBP isoform is FKBP12, which, in a complex with FK506, binds to and inhibits the phosphatase calcineurin (4-6). Subsequently, dephosphorylation and nuclear translocation of nuclear factor of activated T cells (NFAT)1 can no longer occur, leading to the inhibition of the transcription of the IL2 gene, IL2 being the major growth factor for T cells (reviewed in ref. 7). In addition, a recent report has demonstrated that immunophilin-FK506 complexes block the JNK and p38 mitogen-activated protein kinases (MAPKs) during T cell activation and also inhibit IL2 synthesis via these pathways (8). The authors showed that direct inhibitors of calcineurin activity had no effect on JNK and p38 activation, suggesting that FK506 leads to immunosuppression via calcineurin-dependent as well as calcineurin-independent pathways.FKBP52 is another member of the FKBP family that was originally found associated with heat shock protein with a molecular mass of 90 kDa (HSP90) in the heterooligomeric forms of steroid receptor complexes (9, 10). FKBP52 displays a modular organization (11-13) and only the NH 2 -terminal part of the protein is responsible for the immunophilin character of the whole protein; it binds FK506 and rapamycin and displays a peptidylprolyl isomerase function characteristic of the immunophilin family (14). Although this NH 2 -terminal part shares high structural and functional homologies with FKBP12, it does not inhibit the phosphatase activity of calc...

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Section: Discussionmentioning

confidence: 99%

The FKBP-associated protein FAP48 is an antiproliferative molecule and a player in T cell activation that increases IL2 synthesis

Krummrei

Baulieu

Chambraud

2003

Proc. Natl. Acad. Sci. U.S.A.

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“…It may be that an additional protein will enhance the DNA binding and nucleolytic activities of Cyp. Indeed, Cyp binds only weakly to calcineurin by itself, but it shows great affinity for calcineurin with the addition of CsA (58). Thus, there are several possibilities to account for the rate of DNA degradation by Cyps.…”

Section: Discussionmentioning

confidence: 99%

Native Recombinant Cyclophilins A, B, and C Degrade DNA Independently of Peptidylprolyl cis-trans-Isomerase Activity

Montague

Hughes

Cidlowski

1997

Journal of Biological Chemistry

162

122

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Previous work in our laboratory (Montague, J., Gaido, M., Frye, C., and Cidlowski, J. (1994) J. Biol. Chem. 269, 18877-18880) has shown that human recombinant cyclophilins A, B, and C have sequence homology with the apoptotic nuclease NUC18 and that denatured cyclophilins can degrade DNA. We have now evaluated the nucleolytic activity of recombinant cyclophilins under native conditions. We show that nuclease activity inherent to cyclophilins is distinct from cis-trans-peptidylprolyl isomerase activity and is similar to that described for apoptotic nucleases. Cyclophilin nucleolytic activity is stimulated by Ca 2؉ and/or Mg 2؉, with a combination of the two being optimal for cyclophilins A and B. Mg 2؉ alone is sufficient for cyclophilin C nuclease activity. pH optimums are in the range of pH 7.5-9.5. Cyclophilins can degrade both single-stranded and double-stranded DNA. Additionally, cyclophilins produce 3-OH termini in linear double-stranded substrates, suggesting the cuts produced are similar to those of apoptotic cells. Cyclophilins also display endonucleolytic activity, demonstrated by their ability to degrade supercoiled DNA. In the absence of ions, cyclophilins bind linearized DNA. When added to nuclei from nonapoptotic cells, cyclophilin C induces 50-kilobase pair DNA fragmentation but not internucleosomal fragmentation. Together, these data suggest that cyclophilins are involved in degradation of the genome during apoptosis.

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“…Cyclophilin A: Overexpression, Purification, and Generation of Antisera-Wild-type yeast cyclophilin A was tagged with a stretch of six histidines at the amino terminus and overexpressed and purified by Ni 2ϩ -nitrilotriacetic acid-agarose affinity chromatography as described previously (50). The His 6 -cyclophilin A protein was further purified by excision and electroelution from KCl-stained SDS-PAGE gels.…”

Section: Methodsmentioning

confidence: 99%

Mutations That Perturb Cyclophilin A Ligand Binding Pocket Confer Cyclosporin A Resistance in Saccharomycescerevisiae

Cárdenas

Lim

Heitman

1995

Journal of Biological Chemistry

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In complex with the peptidyl-prolyl isomerase cyclophilin A, the immunosuppressive antifungal drug cyclosporin A (CsA) inhibits a Ca 2؉ /calmodulin-dependent protein phosphatase, calcineurin, which regulates signal transduction. We isolated and characterized cyclophilin A mutations that confer CsA resistance in a Saccharomyces cerevisiae strain whose growth is CsAsensitive. Three mutations (G70S, H90Y, and G102A) alter single amino acids conserved between yeast and human cyclophilin A, which structural analyses implicate in CsA binding to human cyclophilin A. By Western analysis, all three mutant proteins are expressed in yeast. In vitro, two purified mutant cyclophilins (G70S, G102A) retain prolyl isomerase activity and have moderately reduced affinity for CsA and calcineurin but, when bound to CsA, do bind and inhibit calcineurin phosphatase activity. In contrast, the purified H90Y mutant cyclophilin is dramatically decreased in prolyl isomerase activity, CsA affinity, and calcineurin binding and inhibition. These studies identify conserved cyclophilin A residues that participate in CsA binding and catalysis.

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Immunophilins interact with calcineurin in the absence of exogenous immunosuppressive ligands.

Cited by 149 publications

References 81 publications

The FKBP-associated protein FAP48 is an antiproliferative molecule and a player in T cell activation that increases IL2 synthesis

The FKBP-associated protein FAP48 is an antiproliferative molecule and a player in T cell activation that increases IL2 synthesis

Native Recombinant Cyclophilins A, B, and C Degrade DNA Independently of Peptidylprolyl cis-trans-Isomerase Activity

Mutations That Perturb Cyclophilin A Ligand Binding Pocket Confer Cyclosporin A Resistance in Saccharomycescerevisiae

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