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Updated: Jul 31, 2025

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

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The adapter protein FADD provides an alternate pathway for entry into the cell cycle by regulating APC/C-Cdh1 E3

Sahezeel Awadia1, Merna Sitto1, Sundaresh Ram2

  • 1Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, Michigan, USA.

The Journal of Biological Chemistry
|May 5, 2023
PubMed

Insights

Fas-associated protein with death domain (FADD) inhibits APC/C-Cdh1, a key regulator of cell cycle arrest. FADD enables cell cycle entry, offering a potential strategy to overcome resistance to CDK4/6 inhibitors.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Biology

Background:

  • The anaphase-promoting complex/cyclosome (APC/C)-Cdc20 homolog 1 (Cdh1) E3 ubiquitin ligase complex is crucial for maintaining G0/G1 cell cycle arrest.
  • Inactivation of APC/C-Cdh1 is a prerequisite for initiating the cell cycle.
  • Oncogenic signaling pathways like EGFR/KRAS can promote cell cycle progression, but their efficacy is often limited by APC/C-Cdh1 activity.

Purpose of the Study:

  • To investigate the novel role of Fas-associated protein with death domain (FADD) in regulating the cell cycle.
  • To elucidate the mechanism by which FADD influences APC/C-Cdh1 activity.
  • To explore FADD as a potential therapeutic target for overcoming resistance to cell cycle inhibitors.

Main Methods:

  • Real-time, single-cell imaging of live cells.
  • Biochemical analysis, including protein interaction studies.
  • Assessment of cell cycle progression in response to FADD manipulation and CDK4/6 inhibition.
  • Analysis of FADD phosphorylation and subcellular localization.

Main Results:

  • FADD acts as an inhibitor of APC/C-Cdh1.
  • FADD deficiency leads to APC/C-Cdh1 hyperactivity and G1 arrest, even with active mitogenic signaling.
  • FADD interacts with Cdh1 via a KEN-box motif, and this interaction is essential for inhibiting APC/C-Cdh1.
  • FADD phosphorylation at Ser-194 by CK1α is required for its nuclear translocation and inhibitory function.
  • Overexpression of wild-type FADD, but not a non-interacting mutant, promotes cell cycle entry independently of CDK4/6-Rb-E2F signaling.

Conclusions:

  • FADD plays a critical role in cell cycle progression by inhibiting APC/C-Cdh1.
  • FADD provides a CDK4/6-Rb-E2F-independent mechanism for cell cycle entry.
  • FADD represents a promising therapeutic target for overcoming CDK4/6 inhibitor resistance in cancer.
Keywords:
APC/CFADDG1/S transitioncell cyclelung canceroncogenerestriction point

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