Quantitative Interactomics in Primary T Cells Provides a Rationale for Concomitant PD-1 and BTLA Coinhibitor Blockade...

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• Coinhibitory receptors like PD-1 and BTLA are crucial regulators of T cell activation.
• Understanding their signaling mechanisms is vital for both fundamental immunology and clinical applications, particularly in cancer immunotherapy.
• The precise roles of SHP-1 and SHP-2 phosphatases in PD-1 and BTLA signaling remain incompletely defined.

Purpose of the Study:

• To quantitatively define the composition and dynamics of PD-1 and BTLA coinhibitory signalosomes in primary T cells.
• To resolve the controversy surrounding the roles of SHP-1 and SHP-2 in PD-1 coinhibition.
• To elucidate the functional redundancy and distinct recruitment patterns of phosphatases by PD-1 and BTLA.

Main Methods:

• Quantitative interactomics to analyze protein complexes.
• Study of primary effector T cells and the T cell-antigen-presenting cell interface.
• Separation and analysis of specific PD-1-phosphatase complexes (PD-1-SHP-1 and PD-1-SHP-2).

Main Results:

• PD-1 primarily recruits SHP-2, but can recruit SHP-1 when SHP-2 is absent, maintaining function.
• BTLA predominantly recruits SHP-1, with some SHP-2 recruitment.
• Both PD-1-SHP-1 and PD-1-SHP-2 complexes equally dampen T cell receptor (TCR) and CD28 signaling pathways.

Conclusions:

• Quantitative interactomics in primary T cells reveals functional redundancy in coinhibitory receptor signaling.
• The distinct and overlapping phosphatase recruitment by PD-1 and BTLA provides a basis for rational design of combination immunotherapies.
• Understanding these signaling pathways can optimize cancer immunotherapy strategies by targeting specific coinhibitory mechanisms.