P2X4 receptors contribute to lysosomal properties and functions

P2X receptors are ligand-gated cation channels that play key roles in the central nervous system (CNS). Among those, P2X4 receptor, the most abundant P2X receptors expressed in the brain including neurons and microglia, are constitutively internalized and retained mainly into the lysosomes with a weak surface expression in normal conditions. Microglia functions have been directly linked to the regulation of lysosomal activity, which contributes to the brain homeostasis. Interestingly, P2X4 preserve their functionality into lysosomes and their activation by intraluminal ATP allows calcium influx, promoting lysosomal fusion. However, it remains uncertain whether P2X4 modulate lysosomal functions on microglial properties.We have recently developed internalization-defective P2X4KI mice increasing surface P2X4 and P2X4KO mice in which P2X4 gene is deleted to better understand its function. Firstly, we evaluated whether such surface increase induce or not the depletion of lysosomal pools of P2X4. P2X4KI mice showed a decreased colocalization of P2X4 and lysosomal markers in microglial cultures, suggesting a decrease on the lysosomal P2X4 pools. We are currently investigating the impact of P2X4 on lysosomal properties from brain and microglia of WT, P2X4KI and P2X4KO mice. By combining cellular and biochemical approaches, we will study whether lysosomal P2X4 expression modulates the size and subcellular distribution of the lysosomes, the intraluminal pH, proteolytic enzymatic activities and autophagic pathways.This work will unravel the role of P2X4 receptors in lysosomal function, providing valuable insights to potentially target multiple pathological conditions impacting lysosomal functions in the CNS.