Discrete LAT condensates encode antigen information from single pMHC:TCR binding events

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• T cell recognition of antigens is crucial for adaptive immunity.
• The linker for activation of T cells (LAT) protein forms 2D condensates, a key feature in T cell antigen discrimination.
• Understanding the dynamics of LAT condensation and its relationship with T cell receptor (TCR) binding is essential.

Purpose of the Study:

• To investigate the spatial and temporal dynamics of LAT condensation in response to pMHC:TCR binding events.
• To determine how the duration of pMHC:TCR binding influences LAT condensate formation, size, and lifetime.
• To elucidate the role of LAT condensation in setting antigen discrimination thresholds in T cells.

Main Methods:

• Utilized single-molecule imaging techniques to track individual pMHC:TCR binding events.
• Simultaneously monitored LAT condensation dynamics at the cell membrane.
• Analyzed the correlation between pMHC:TCR binding dwell time and LAT condensate properties.

Main Results:

• Individual pMHC:TCR binding events are sufficient to initiate LAT condensation.
• LAT condensates are self-limiting, with size and lifetime independent of binding event duration.
• The probability of LAT condensate formation correlates with pMHC:TCR binding dwell time.
• LAT condensation occurs abruptly after a significant delay, and a mutation affecting PLC-γ1 recruitment alters this delay and T cell specificity.

Conclusions:

• LAT protein condensation functions as a critical phase transition in T cell antigen discrimination.
• The probability of LAT condensate formation, rather than its physical characteristics, is modulated by antigen binding dwell time.
• LAT condensation dynamics play a role in establishing the thresholds for T cell antigen specificity.