CTLA4 ligation attenuates AP-1, NFAT and NF-kappaB activity in activated T cells

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Cytotoxic T-Lymphocyte-Associated protein 4 (CTLA4) is a T cell surface receptor known to inhibit T cell proliferation.
• The precise mechanisms by which CTLA4 exerts its inhibitory effects, particularly its timing and molecular targets, remain incompletely understood.

Purpose of the Study:

• To investigate how CTLA4 ligation inhibits activated T cell proliferation.
• To determine the influence of CTLA4 on the activity of nuclear transcription factors AP-1, NFAT, and NF-kappaB.

Main Methods:

• Cross-linking of CTLA4 on activated T cells.
• Assessing the activity of transcription factors AP-1, NFAT, and NF-kappaB.
• Measuring T cell proliferation.
• Evaluating DNA binding activity of transcription factors.
• Investigating the role of TCR and CD28 signaling in CTLA4 function.

Main Results:

• CTLA4 cross-linking completely blocked AP-1 and NFAT activity before observable effects on proliferation.
• NF-kappaB activity was less affected compared to AP-1 and NFAT.
• Suppression of AP-1 and NFAT transcriptional activity correlated with reduced DNA binding as early as 10 hours post-activation.
• CTLA4 inhibition of proliferation and transcription factor activity occurred independently of CD28 stimulation and required proximity to signaling TCR complexes.

Conclusions:

• CTLA4 acts early in T cell activation to inhibit proliferation.
• CTLA4 suppresses the activity of crucial nuclear transcription factors, including AP-1 and NFAT.
• These findings reveal an early inhibitory role for CTLA4 in T cell activation pathways.