Protein phosphatase 4 negatively regulates LPS cascade by inhibiting ubiquitination of TRAF6

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• Toll-like receptor (TLR) signaling pathways are crucial for innate immunity.
• TRAF6 (TNF receptor-associated factor 6) is a central E3 ubiquitin ligase in TLR/IL-1R signaling.
• Understanding TRAF6-interacting proteins is key to elucidating pathway regulation.

Purpose of the Study:

• To identify novel TRAF6-interacting proteins.
• To investigate the role of PP4 in the LPS/TLR4 signaling pathway.
• To determine if PP4 modulates TRAF6-mediated NF-kappaB activation.

Main Methods:

• Yeast two-hybrid screening to identify TRAF6-interacting proteins.
• Co-immunoprecipitation assays to confirm physical interaction between PP4 and TRAF6.
• Analysis of NF-kappaB activation and TRAF6 ubiquitination in response to LPS stimulation.
• Quantitative PCR to assess PP4 gene expression.

Main Results:

• PP4 was identified as a TRAF6-interacting protein via yeast two-hybrid screening.
• PP4 physically interacts with TRAF6 and is recruited to the TLR4 complex upon LPS stimulation.
• PP4 negatively regulates LPS-induced and TRAF6-mediated NF-kappaB activation by inhibiting TRAF6 ubiquitination.
• LPS stimulation leads to an increase in PP4 expression.

Conclusions:

• PP4 is a novel negative feedback regulator of the LPS/TLR4 signaling pathway.
• PP4 modulates TLR4 signaling by interacting with TRAF6 and inhibiting its ubiquitination.
• These findings provide new insights into the molecular mechanisms governing TLR4 pathway homeostasis.