Casein kinase Iepsilon plays a functional role in the transforming growth factor-beta signaling pathway.

Journal Article (Journal Article)

The transforming growth factor-beta (TGF-beta) signaling pathway is known to be involved in a wide range of biological events, including development, cellular differentiation, apoptosis, and oncogenesis. The TGF-beta signal is mediated by ligand binding to the type II receptor, leading to the recruitment and activation of the type I receptor, and subsequent activation of a family of intracellular signal transducing proteins called Smads. Here we report a regulatory role for casein kinase Iepsilon (CKIepsilon) in the TGF-beta signaling cascade. We find that CKIepsilon binds to all Smads and the cytoplasmic domains of the type I and type II receptors both in vitro and in vivo. The interaction of CKIepsilon with the type I and type II receptors is independent of TGF-beta stimulation, whereas the CKIepsilon/Smad interaction is transiently disrupted by ligand treatment. Additionally, CKIepsilon is able to phosphorylate the receptor-activated Smads (Smads 1-3 and 5) and the type II receptor in vitro. Transcriptional reporter assays reveal that transient overexpression of wild type CKIepsilon dramatically reduces basal reporter activity but enhances TGF-beta-stimulated transcription. Furthermore, overexpression of a kinase-dead mutant of CKIepsilon inhibits both basal and ligand-induced transcription, whereas inhibition of endogenous CKI catalytic activity with IC261 blocks only TGF-beta-stimulated reporter activity. Finally, knocking down CKIepsilon protein levels results in a significant increase in basal and TGF-beta-induced transcription. These results suggest that CKIepsilon plays a ligand-dependent, differential, and dual regulatory role within the TGF-beta signaling pathway.

Full Text

Duke Authors

Cited Authors

  • Waddell, DS; Liberati, NT; Guo, X; Frederick, JP; Wang, X-F

Published Date

  • July 9, 2004

Published In

Volume / Issue

  • 279 / 28

Start / End Page

  • 29236 - 29246

PubMed ID

  • 15133026

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.M400880200


  • eng

Conference Location

  • United States