TLR4/MD-2 is a receptor for extracellular nucleophosmin 1

Area of Science:

• Immunology
• Molecular Biology

Background:

• Nucleophosmin 1 (NPM1) is released by damaged cells and promotes inflammation, acting as a damage-associated molecular pattern (DAMP).
• The specific receptor for extracellular NPM1 and its signaling pathway remain largely unknown.
• Toll-like receptors (TLRs) are known to bind DAMPs, suggesting a potential role in NPM1 recognition.

Purpose of the Study:

• To identify the receptor for extracellular Nucleophosmin 1 (NPM1).
• To elucidate the signaling pathway activated by NPM1.
• To investigate the therapeutic potential of targeting the NPM1-receptor interaction.

Main Methods:

• Utilized differentiated THP-1 cells to assess NPM1-induced cytokine production and ERK1/2 activation.
• Employed TLR4 antagonists (LPS-Rhodobacter sphaeroides, an MD-2 antagonist) and a TLR4 signaling inhibitor (TAK-242).
• Performed far-western blot analysis to confirm direct binding between NPM1 and MD-2.

Main Results:

• NPM1-induced tumor necrosis factor-alpha (TNF-α) production and ERK1/2 activation were significantly inhibited by TLR4 pathway antagonists.
• Far-western blot analysis demonstrated a direct binding interaction between NPM1 and myeloid differentiation protein-2 (MD-2).
• These findings strongly suggest that TLR4 acts as the receptor for NPM1.

Conclusions:

• Toll-like receptor 4 (TLR4) is identified as the receptor for extracellular Nucleophosmin 1 (NPM1).
• NPM1 signaling is mediated through the TLR4/MD-2 complex.
• Inhibiting NPM1 activity presents a potential novel therapeutic strategy for TLR4-related inflammatory diseases.