T-cell protrusions enable fast, localised initiation of chimeric antigen receptor signalling

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• T cell protrusions are crucial for migration, antigen surveillance, and immune signaling.
• Understanding how these structures initiate T cell activation signaling is vital for immunotherapy development.

Purpose of the Study:

• To investigate the role of T cell protrusions in initiating signaling pathways for T cell activation.
• To visualize and quantify protein dynamics within protrusions during chimeric antigen receptor (CAR) T cell interactions with target cells.

Main Methods:

• Live-cell imaging of endogenously tagged proteins in HER2-specific CAR T cells.
• Quantitative super-resolution STED microscopy to monitor protein rearrangement and membrane topology.
• Correlating protein dynamics with T cell activation events upon contact with HER2+ breast cancer cells.

Main Results:

• Signaling proteins (Lck, CD45, LAT, CAR) were not pre-enriched in protrusions before activation.
• Upon target cell contact, rapid protein reorganization and CAR clustering occurred preferentially within protrusions.
• Enhanced recruitment of ZAP-70 and LAT was observed in protrusions, alongside CD45 exclusion.
• Signaling machinery rearranged more effectively in protrusions than in the main plasma membrane.

Conclusions:

• T cell protrusions act as key sites for enhanced receptor activation through protein clustering and exclusion dynamics.
• Protrusions facilitate faster and more effective signaling initiation compared to other membrane regions.
• This mechanism reframes the understanding of T cell activation initiation at cell-cell contacts.