Effects of the ecto-ATPase apyrase on microglial ramification and surveillance reflect cell depolarization, not ATP depletion

摘要: Microglia, the brain’s innate immune cells, have highly motile processes which constantly survey brain to detect infection, remove dying and prune synapses during development. ATP released by tissue damage is known attract microglial processes, but it controversial whether an ambient level of needed promote constant surveillance in normal brain. Applying ATPase apyrase, enzyme hydrolyzes ADP, reduces process ramification surveillance, suggesting that ATP/ADP maintains surveillance. However, attempting raise blocking endogenous ecto-ATPase (termed NTPDase1/CD39), also ATP/ADP, does not affect cells’ or nor their membrane currents, respond even small rises extracellular [ATP] [ADP] with activation K+ channels. This indicates a lack detectable activity, contradicting results apyrase. We resolve this contradiction demonstrating contamination commercially available apyrase high concentration depolarizing microglia. Exposure same (without added) reduced as Dialysis retained its ATP-hydrolyzing activity abolished depolarization decrease produced undialyzed enzyme. Thus, applying affects microglia action independent ATP, no purinergic signaling required maintain These implications for hundreds prior studies employed hydrolyze ATP/ADP.