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A novel transforming growth factor-beta receptor-interacting protein that is also a light chain of the motor protein

Qian Tang1, Cory M Staub, Guofeng Gao

  • 1Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.

Molecular Biology of the Cell
|December 12, 2002
PubMed

Insights

Researchers discovered a link between transforming growth factor-beta (TGFbeta) signaling and dynein, a motor protein. This protein, mLC7-1, interacts with TGFbeta receptors and influences cell growth, suggesting a novel mechanism for TGFbeta pathway regulation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cytoskeletal Dynamics

Background:

  • Transforming growth factor-beta (TGFbeta) is a critical cytokine regulating cell growth and differentiation.
  • TGFbeta signaling pathways involve receptor kinases and downstream effectors.
  • The precise mechanisms of TGFbeta receptor-mediated intracellular signaling are still being elucidated.

Purpose of the Study:

  • To identify novel proteins interacting with activated TGFbeta receptors.
  • To investigate the role of identified proteins in TGFbeta-induced cellular responses.
  • To explore the potential connection between TGFbeta signaling and the dynein motor complex.

Main Methods:

  • Screening of a TGFbeta-responsive intestinal epithelial cell line expression library using phosphorylated TGFbeta receptor domains.
  • Co-immunoprecipitation and Western blotting to confirm protein interactions and phosphorylation.
  • Forced expression studies to assess the functional impact of the identified protein on TGFbeta signaling.
  • Analysis of protein localization and recruitment to dynein components.

Main Results:

  • Isolation and identification of the mammalian homologue of the LC7 family (mLC7) of dynein light chains (DLCs) as a TGFbeta receptor-interacting protein.
  • Demonstration that mLC7-1 interacts with the TGFbeta receptor complex and is phosphorylated upon ligand stimulation.
  • Forced expression of mLC7-1 recapitulates key TGFbeta responses, including JNK activation, c-Jun phosphorylation, and growth inhibition.
  • Evidence that TGFbeta signaling induces the recruitment of mLC7-1 to the dynein intermediate chain (DIC).

Conclusions:

  • This study reveals the first link between cytoplasmic dynein and a growth inhibitory cytokine, TGFbeta.
  • mLC7-1 acts as a novel intracellular component of the TGFbeta receptor complex.
  • The findings suggest that TGFbeta signaling may utilize dynein light chains for cargo recruitment and intracellular transport along microtubules.

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