RGD Reference Report - Molecular mechanisms of TGF beta receptor-triggered signaling cascades rapidly induced by the calcineurin inhibitors cyclosporin A and FK506. - Rat Genome Database

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Molecular mechanisms of TGF beta receptor-triggered signaling cascades rapidly induced by the calcineurin inhibitors cyclosporin A and FK506.

Authors: Akool el-S, 2008  Doller, A  Babelova, A  Tsalastra, W  Moreth, K  Schaefer, L  Pfeilschifter, J  Eberhardt, W 
Citation: Akool el-S, etal., J Immunol. 2008 Aug 15;181(4):2831-45.
RGD ID: 2302517
Pubmed: PMID:18684975   (View Abstract at PubMed)

The calcineurin inhibitor (CNI)-induced renal fibrosis is attributed to an exaggerated deposition of extracellular matrix, which is mainly due to an increased expression of TGFbeta. Herein we demonstrate that the CNI cyclosporin A and tacrolimus (FK506), independent of TGFbeta synthesis, rapidly activate TGFbeta/Smad signaling in cultured mesangial cells and in whole kidney samples from CNI-treated rats. By EMSA, we demonstrate increased DNA binding of Smad-2, -3, and -4 to a cognate Smad-binding promoter element (SBE) accompanied by CNI-triggered activation of Smad-dependent expression of tissue inhibitor of metalloprotease-1 (TIMP-1) and connective tissue growth factor. Using an activin receptor-like kinase-5 (ALK-5) inhibitor and by small interfering RNA we depict a critical involvement of both types of TGFbeta receptors in CNI-triggered Smad signaling and fibrogenic gene expression, respectively. Mechanistically, CNI cause a rapid activation of latent TGFbeta, which is prevented in the presence of the antioxidant N-acetyl cysteine. A convergent activation of p38 MAPK is indicated by the partial blockade of CNI-induced Smad-2 activation by SB203580; conversely, both TGFbeta-RII and TGFbeta are critically involved in p38 MAPK activation by CNI. Activation of both signaling pathways is similarly triggered by reactive oxygen species. Finally, we show that neutralization of TGFbeta markedly reduced the CNI-dependent Smad activation in vitro and in vivo. Collectively, this study demonstrates that CNI via reactive oxygen species generation activate latent TGFbeta and thereby initiate the canonical Smad pathway by simultaneously activating p38 MAPK, which both synergistically induce Smad-driven gene expression.



Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Tgfbr1Rattransforming growth factor beta receptor signaling pathway  IMP  RGD 
Tgfbr2Rattransforming growth factor beta receptor signaling pathway  IMP  RGD 

Molecular Function

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Tgfbr1Rattransforming growth factor beta receptor activity, type I  IMP  RGD 
Tgfbr2Rattransforming growth factor beta receptor activity, type II  IMP  RGD 

Molecular Pathway Annotations    Click to see Annotation Detail View
Objects Annotated

Genes (Rattus norvegicus)
Smad2  (SMAD family member 2)
Tgfbr1  (transforming growth factor, beta receptor 1)
Tgfbr2  (transforming growth factor, beta receptor 2)

Genes (Mus musculus)
Smad2  (SMAD family member 2)
Tgfbr1  (transforming growth factor, beta receptor I)
Tgfbr2  (transforming growth factor, beta receptor II)

Genes (Homo sapiens)
SMAD2  (SMAD family member 2)
TGFBR1  (transforming growth factor beta receptor 1)
TGFBR2  (transforming growth factor beta receptor 2)

Objects referenced in this article
Gene Smad4 SMAD family member 4 Rattus norvegicus

Additional Information