Ninjurin1 regulates lipopolysaccharide-induced inflammation through direct binding

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Ninjurin1 is a transmembrane protein implicated in macrophage functions during inflammation.
• Previous studies suggest Ninjurin1 repression attenuates lipopolysaccharide (LPS)-induced inflammation, but the mechanism is unclear.

Purpose of the Study:

• To elucidate the mechanism by which Ninjurin1 modulates LPS-induced inflammatory responses in macrophages.
• To investigate the direct interaction between Ninjurin1 and LPS.

Main Methods:

• Pull-down assays using HEK293T cells expressing Ninjurin1 and biotinylated LPS.
• LPS binding assays with truncated Ninjurin1 protein variants.
• Ninjurin1 knockdown using siRNA in Raw264.7 cells followed by LPS stimulation.

Main Results:

• LPS directly binds to Ninjurin1, confirmed by pull-down assays.
• Amino acids 81-100 of Ninjurin1 are essential for LPS binding.
• Ninjurin1 knockdown significantly reduced nitric oxide (NO) and tumor necrosis factor-α (TNFα) secretion upon LPS treatment.

Conclusions:

• Ninjurin1 directly binds to LPS, mediating the inflammatory response.
• Ninjurin1 is a critical regulator of LPS-induced inflammation.
• Ninjurin1 represents a potential therapeutic target for inflammatory conditions like sepsis and inflammation-associated carcinogenesis.