Proapoptotic RYBP interacts with FANK1 and induces tumor cell apoptosis through the AP-1 signaling pathway

Area of Science:

• Molecular Biology
• Cell Biology
• Oncology

Background:

• Ring1 and YY1 Binding Protein (RYBP) is known to induce tumor-specific apoptosis.
• The precise molecular mechanisms underlying RYBP's pro-apoptotic function remain incompletely elucidated.

Purpose of the Study:

• To identify novel RYBP-interacting proteins.
• To elucidate the molecular mechanism by which RYBP mediates tumor cell apoptosis.

Main Methods:

• Yeast two-hybrid screening to identify RYBP-interacting proteins.
• Coimmunoprecipitation, GST pulldown, and immunofluorescence assays to confirm protein interactions.
• Western blotting and shRNA knockdown to assess protein expression and stability.
• Proteasome degradation assays and AP-1 signaling pathway analysis.

Main Results:

• Fibronectin type III and ankyrin repeat domains 1 (FANK1) was identified as a novel RYBP-interacting protein.
• The N-terminal FNIII domain of FANK1 interacts with the C-terminal Serine/Threonine-rich region of RYBP.
• RYBP overexpression stabilized FANK1 expression, while RYBP knockdown reduced FANK1 levels.
• RYBP was found to inhibit the proteasome degradation of polyubiquitinated FANK1, extending its half-life.
• RYBP activates the FANK1-mediated activator protein 1 (AP-1) signaling pathway, contributing to tumor cell apoptosis.

Conclusions:

• RYBP interacts with FANK1, stabilizing its protein levels by inhibiting proteasome degradation.
• RYBP activates FANK1-mediated AP-1 signaling, which plays a role in tumor cell apoptosis.
• This study uncovers a novel mechanism for RYBP's pro-apoptotic activity in human tumor cells.