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Fas-associated death domain protein interacts with methyl-CpG binding domain protein 4: a potential link between

Robert A Screaton1, Stephan Kiessling, Owen J Sansom

  • 1The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.

Proceedings of the National Academy of Sciences of the United States of America
|April 19, 2003
PubMed

Insights

Fas-associated death domain protein (FADD) is surprisingly found in the nucleus, not cytoplasm. This nuclear FADD interacts with DNA repair proteins and influences apoptosis, suggesting a new role beyond traditional death receptor signaling.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Fas-associated death domain protein (FADD) is known as a cytoplasmic adaptor protein linking death receptors to initiator caspases.
  • The subcellular localization and nuclear functions of endogenous FADD have not been previously reported.

Purpose of the Study:

  • To investigate the localization of endogenous FADD within cells.
  • To identify potential nuclear binding partners of FADD.
  • To elucidate novel functions of FADD beyond its canonical role in death receptor signaling.

Main Methods:

  • Immunofluorescence microscopy to determine FADD localization in various adherent cell lines.
  • Co-immunoprecipitation assays to identify FADD interacting proteins.
  • Analysis of FADD phosphorylation site mutants and their interaction with exportin-5.
  • Assessment of MBD4-mediated apoptosis regulation.

Main Results:

  • Endogenous FADD is predominantly localized in the nucleus of several adherent cell lines.
  • Nuclear accumulation and cytoplasmic export of FADD depend on phosphorylation at Ser-194 and interaction with exportin-5.
  • FADD interacts with methyl-CpG binding domain protein 4 (MBD4), a DNA repair protein, and MLH1 within the nucleus.
  • MBD4, in complex with FADD, regulates apoptosis induced by DNA damage, Fas ligand, and cell detachment.

Conclusions:

  • FADD exhibits a predominantly nuclear localization, challenging its established cytoplasmic role.
  • Nuclear FADD interacts with the DNA repair protein MBD4, suggesting a novel function in genome surveillance and DNA repair-associated apoptosis.
  • This discovery reveals a new paradigm for FADD function, extending beyond its classical involvement in death receptor-mediated apoptosis pathways.

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