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Sci Signal. 2015 Jan 6;8(358):ra1. doi: 10.1126/scisignal.2005379.

The kinase activity of the Ser/Thr kinase BUB1 promotes TGF-β signaling.

Author information

1
Center for Molecular Imaging, University of Michigan, Ann Arbor, MI 48109, USA. Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA.
2
Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA.
3
Single Molecule Analysis in Real-Time (SMART) Center, University of Michigan, Ann Arbor, MI 48109, USA. Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
4
Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA.
5
Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA.
6
Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA. Michigan Center for Translational Pathology, University of Michigan, Ann Arbor, MI 48109, USA.
7
Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
8
Center for Molecular Imaging, University of Michigan, Ann Arbor, MI 48109, USA. Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA.
9
Center for Molecular Imaging, University of Michigan, Ann Arbor, MI 48109, USA. Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA. alnawaz@med.umich.edu.

Abstract

Transforming growth factor-β (TGF-β) signaling regulates cell proliferation and differentiation, which contributes to development and disease. Upon binding TGF-β, the type I receptor (TGFBRI) binds TGFBRII, leading to the activation of the transcription factors SMAD2 and SMAD3. Using an RNA interference screen of the human kinome and a live-cell reporter for TGFBR activity, we identified the kinase BUB1 (budding uninhibited by benzimidazoles-1) as a key mediator of TGF-β signaling. BUB1 interacted with TGFBRI in the presence of TGF-β and promoted the heterodimerization of TGFBRI and TGFBRII. Additionally, BUB1 interacted with TGFBRII, suggesting the formation of a ternary complex. Knocking down BUB1 prevented the recruitment of SMAD3 to the receptor complex, the phosphorylation of SMAD2 and SMAD3 and their interaction with SMAD4, SMAD-dependent transcription, and TGF-β-mediated changes in cellular phenotype including epithelial-mesenchymal transition (EMT), migration, and invasion. Knockdown of BUB1 also impaired noncanonical TGF-β signaling mediated by the kinases AKT and p38 MAPK (mitogen-activated protein kinase). The ability of BUB1 to promote TGF-β signaling depended on the kinase activity of BUB1. A small-molecule inhibitor of the kinase activity of BUB1 (2OH-BNPP1) and a kinase-deficient mutant of BUB1 suppressed TGF-β signaling and formation of the ternary complex in various normal and cancer cell lines. 2OH-BNPP1 administration to mice bearing lung carcinoma xenografts reduced the amount of phosphorylated SMAD2 in tumor tissue. These findings indicated that BUB1 functions as a kinase in the TGF-β pathway in a role beyond its established function in cell cycle regulation and chromosome cohesion.

PMID:
25564677
PMCID:
PMC4440544
DOI:
10.1126/scisignal.2005379
[Indexed for MEDLINE]
Free PMC Article

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