Inhibition of transforming growth factor-beta signaling by low molecular weight compounds interfering with ATP- or substrate-binding sites of the TGF beta type I receptor kinase

• Transforming growth factor-beta (TGFbeta) is a potent regulator of cell proliferation, differentiation, apoptosis, and migration. TGF-beta type I receptor (TbetaR-I), which has intrinsic serine/threonine kinase activity, is a key component in activation of intracellular TGFbeta signaling. We studied two different classes of TbetaR-I inhibitors, i.e., compounds interfering with the ATP-binding site of the kinase and substrate-mimicking peptides. We found that pyridinylimidazole compounds inhibited TbetaR-I kinase at micromolar concentration. A representative compound, SB203580, inhibited in vivo Smad2 phosphorylation by TbetaR-I and affected TGFbeta-dependent transcriptional activation. Peptides mimicking the TbetaR-I phosphorylation sites at the C-terminus of Smad2 also inhibited the autophosphorylation of TbetaR-I and phosphorylation of Smad2 by TbetaR-I in vitro and in vivo, whereas a similar peptide from Smad5 was without effect. The substrate-mimicking peptide, fused to penetratin, inhibited a TGFbeta1-dependent transcriptional response in a luciferase reporter assay and ligand-dependent growth inhibition of Mv1Lu cells. Thus, the substrate-mimetic peptide is a new type of specific inhibitor of the TGFbeta signaling in vivo.

Nyckelord

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine/pharmacology

Adenosine Triphosphate/antagonists & inhibitors/*metabolism

Amino Acid Sequence

Animals

Antennapedia Homeodomain Protein

Binding Sites/drug effects

COS Cells

Cell Line

DNA-Binding Proteins/metabolism/pharmacology

Enzyme Inhibitors/pharmacology

Homeodomain Proteins/pharmacology

Imidazoles/pharmacology

Mink

Molecular Mimicry

Molecular Sequence Data

Molecular Weight

Nuclear Proteins

Peptide Fragments/chemical synthesis/pharmacology

Protein-Serine-Threonine Kinases/*antagonists & inhibitors/genetics/metabolism

Pyridines/pharmacology

Receptors; Transforming Growth Factor beta/*antagonists & inhibitors/metabolism

Recombinant Fusion Proteins/chemical synthesis/pharmacology

Signal Transduction/drug effects

Smad2 Protein

Smad3 Protein

Substrate Specificity

Trans-Activators/metabolism/pharmacology

Transcription Factors

Transforming Growth Factor beta/*antagonists & inhibitors/metabolism/*physiology

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