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

  • Sci Signal. 2015 Jan 6;8(358):ra1. doi: 10.1126/scisignal.2005379.
Shyam Nyati  1 ,  Katrina Schinske-Sebolt  2 ,  Sethuramasundaram Pitchiaya  3 ,  Katerina Chekhovskiy  2 ,  Areeb Chator  2 ,  Nauman Chaudhry  2 ,  Joseph Dosch  4 ,  Marcian E Van Dort  4 ,  Sooryanarayana Varambally  5 ,  Chandan Kumar-Sinha  6 ,  Mukesh Kumar Nyati  2 ,  Dipankar Ray  2 ,  Nils G Walter  3 ,  Hongtao Yu  7 ,  Brian Dale Ross  8 ,  Alnawaz Rehemtulla  9
Affiliations
  • 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. [email protected].
PMID: 25564677 DOI: 10.1126/scisignal.2005379
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.

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