P2RX4 and amyotrophic lateral sclerosis: We observed a potentiation of ATP-induced P2X4 currents as well as an increase in P2X4 surface/total ratio in heterologous cells co-expressing mP2X4 receptors and different ALS human mutant SOD1 proteins (SOD1-G93A, G85R and G37R) compared to cells expressing WT human SOD1.