Mitochondrial Superoxide Generation Enhances P2X7R-mediated Loss of Cell Surface CD62L on Naïve Human CD4+ T Lymphocytes1

• Published in: The Journal of immunology (1950) 2013-01, Vol.190 (4), p.1551-1559
• Main Authors: Foster, John G., Carter, Edward, Kilty, Iain, MacKenzie, Amanda B., Ward, Stephen G.
• Format: Article
• Language: English
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.1201510

Migration of naïve CD4 + T lymphocytes into lymphoid tissue is essential for their activation and subsequent roles in adaptive immunity. The adhesion molecule CD62L, critical for this process, is highly expressed on naïve CD4 + T lymphocytes and is down-regulated upon T lymphocyte activation. We demonstrate protein expression of P2X7R on naïve CD4 + T lymphocytes and show functional channel activity in whole cell patch clamp recordings. CD62L down-regulation occurs rapidly in response to extracellular ATP, a process which is blocked by selective antagonists of P2X7R. This loss of surface CD62L expression was not associated with externalization of phosphatidyl serine. While investigating the mechanisms for this process we revealed that pharmacological modulation of mitochondrial complex I or III, but not inhibition of NADPH oxidase, enhanced P2X7R dependent CD62L down-regulation by increasing ATP potency. Enhanced superoxide generation in the mitochondria of Rotenone and Antimycin A treated cells was observed and may contribute to the enhanced sensitivity of P2X7R to ATP. P2X7R dependent exposure of phosphatidylserine was also revealed by pre-incubation with mitochondrial un-couplers prior to ATP treatment. This may present a novel mechanism whereby P2X7R dependent PS exposure occurs only when cells have enhanced mitochondrial ROS generation. The clearance of apoptotic cells may therefore be enhanced by this mechanism which requires functional P2X7R expression.