The nonreceptor tyrosine kinase c-Src attenuates SCF(β-TrCP) E3-ligase activity abrogating Taz proteasomal...

Area of Science:

• Molecular Oncology
• Cell Signaling
• Virology

Background:

• Polyomavirus middle T antigen (PyMT) oncogene activates c-Src and Hippo pathway effectors Yap and Taz.
• Yap and Taz are key transcription coactivators in oncogenesis, regulated by the Hippo pathway kinase Lats1/2.
• Lats1/2 promotes Yap/Taz ubiquitination and degradation via the SCF(β-TrCP) E3 ligase.

Purpose of the Study:

• To elucidate the mechanism by which PyMT increases cytoplasmic Taz levels.
• To investigate the role of Src tyrosine kinase in regulating Taz stability and degradation.
• To determine if Src affects other SCF(β-TrCP) substrates.

Main Methods:

• Utilized PyMT-induced Src activation models in cellular systems.
• Assessed the degradation of wild-type and mutant Taz proteins.
• Examined the activity of the SCF(β-TrCP) E3 ligase.
• Investigated the degradation of IkB, a known β-TrCP substrate.

Main Results:

• PyMT-induced Src activation inhibits the proteasomal degradation of Taz.
• Src directly attenuates SCF(β-TrCP) E3-ligase activity, preventing Taz degradation.
• Src-mediated rescue of Taz from degradation enhances cell proliferation in dense cultures.
• Src also rescues IkB from β-TrCP-mediated degradation, indicating a broader role.

Conclusions:

• Src tyrosine kinase is a key regulator of SCF(β-TrCP) E3-ligase activity.
• Src's inhibition of Taz degradation contributes to PyMT-driven oncogenesis.
• Src impacts the stability of multiple β-TrCP substrates, suggesting a significant role in cellular regulation.