The role of the P2X7 receptor in the retina: Cell signalling and dysfunction

Abstract

Adenosine 5′-triphosphate (ATP) acts as a signalling molecule within the retina. It can be released like a traditional neurotransmitter via exocytosis, but non-classical mechanisms for release have also been demonstrated. ATP and its breakdown products act at a range of purine receptor subclasses, P1, P2X and P2Y, which are expressed by all cell types of the retina. The P2X-receptors are ligand-gated ion channels and seven subclasses (P2X1-7) have been identified. In particular, the P2X7 receptor subclass is unique; it is relatively insensitive to ATP and it has a long intracellular C-terminus, which is not only critical for ion channel function, but also allows the formation of a pore in the plasma membrane following prolonged stimulation with ATP, which is permeable to molecules up to 900 kDa. This unique activity means the P2X7 receptor has been found to be involved in a range of physiological and pathological roles. In the retina, the receptor is expressed by neurons, macroglia and microglia. This review focuses on the role of the P2X7 receptor in these retinal tissues under physiological conditions and during disease. © 2012 Springer Science+Business Media, LLC.