Signalling to suit function: tailoring phosphoinositide 3-kinase during T-cell activation

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• CD28 family co-receptors (e.g., CD28, ICOS, CTLA-4, BTLA) are critical for T-cell activation outcomes.
• These receptors interact with B7 family ligands, mediating either costimulation or coinhibition of T-cell responses.
• Both costimulatory and coinhibitory receptors engage with class 1A phosphoinositide 3-kinase (PI3K).

Purpose of the Study:

• To investigate the mechanisms by which CD28 family receptors differentially regulate the PI3K-Akt signaling pathway.
• To elucidate how distinct regulation of PI3K-Akt signaling contributes to the functional divergence of these co-receptors.

Main Methods:

• Analysis of PI3K-Akt signaling pathway activation.
• Examination of interactions between CD28 family receptors and class 1A PI3K.
• Investigation of mechanisms opposing Akt activation by co-inhibitory receptors.

Main Results:

• CD28 and inducible costimulator (ICOS) activate PI3K and its downstream effector Akt.
• Cytotoxic T lymphocyte antigen-4 (CTLA-4) and B and T lymphocyte attenuator (BTLA) oppose Akt activation.
• Distinct mechanisms underlie the inhibition of Akt activation by different co-inhibitory receptors.

Conclusions:

• Differential regulation of the PI3K-Akt pathway by CD28 family receptors dictates their opposing roles in T-cell activation.
• Understanding these distinct regulatory mechanisms is key to comprehending T-cell immunity and developing targeted therapies.