Information processing in the NF-κB pathway

Area of Science:

• Cellular signaling and systems biology
• Molecular mechanisms of immune response

Background:

• The Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway is critical for cellular responses.
• Previous understanding suggested the NF-κB pathway transmits only one bit of information regarding stimulus levels.

Purpose of the Study:

• To investigate how tumor necrosis factor (TNF) concentration information is converted into a binary cellular decision.
• To quantify information transmission and discernibility at various stages of the NF-κB pathway.

Main Methods:

• Combined experimental approaches with mathematical modeling.
• Utilized Kolmogorov-Smirnov distance to assess the cell's ability to differentiate between eight TNF concentrations.
• Investigated the effects of translation inhibitor cycloheximide on NF-κB activation.

Main Results:

• Signal discernibility decreases along the NF-κB pathway, with noise limiting low TNF concentration detection and saturation limiting high concentration detection.
• Optimal TNF concentration discernibility occurs between 0.03 and 1 ng/ml.
• Cycloheximide treatment prolonged NF-κB activation and increased NF-κB inhibitor transcript levels (IκBα and A20), indicating information integration over time.

Conclusions:

• The NF-κB pathway functions as a feedback-controlled decision-making module, not just an information transmitter.
• The system integrates information about stimuli over longer time courses, influencing gene expression beyond initial binary responses.