Extracellular NAD and ATP: Partners in immune cell modulation

Area of Science:

• Immunology
• Cellular Signaling
• Biochemistry

Background:

• Extracellular nucleotides like NAD and ATP modulate immune cell functions.
• These nucleotides are catabolized by enzymes, maintaining low steady-state concentrations and generating signaling metabolites.
• NAD and ATP signal through distinct pathways, including purinergic receptors and ADP-ribosyltransferases (ARTs).

Purpose of the Study:

• To elucidate the distinct mechanisms of P2X7 receptor activation by extracellular NAD and ATP.
• To investigate the role of NAD-induced cell death (NICD) in immune regulation.
• To understand how extracellular nucleotide signaling impacts T cell populations during inflammation.

Main Methods:

• Comparative analysis of P2X7 receptor activation by NAD and ATP.
• Investigation of ART-dependent signaling pathways.
• Assessment of cell death induction and T cell population dynamics under inflammatory conditions.

Main Results:

• ATP directly activates P2X7 receptors at high concentrations, while NAD requires ART-dependent ADP-ribosylation for activation.
• NAD-dependent P2X7 activation is more stable and occurs at lower concentrations than ATP-dependent activation.
• NICD specifically targets naive/resting T cells expressing ARTs, leading to cell death.

Conclusions:

• Extracellular NAD and ATP differentially activate the P2X7 receptor, influencing immune cell fate.
• NICD serves as a mechanism to regulate T cell populations, potentially preventing autoimmunity and shaping adaptive immune responses.
• These findings highlight the complex role of extracellular nucleotides as danger signals in immunity.