Pharmacological inhibition of mitochondrial soluble adenylyl cyclase in astrocytes causes activation of AMP-activated protein kinase and induces breakdown of glycogen

Astrocytes contain the majority of the brain’s supply of glycogen which has been suggested to play an important role in neuronal synaptic plasticity. This may be mediated by release of glycogen-derived lactate or glutamine supporting neuronal metabolism or via induction of neuronal signaling pathways. The second messenger cyclic AMP (cAMP) can induce glycogen breakdown and activation of cytosolic soluble adenylyl cyclase (sAC) in astrocytes has been suggested to be the link between neuronal depolarization and glycogen breakdown. However, recent studies have revealed that sAC residing in the mitochondria rather than the cytosol is regulating mitochondrial bioenergetics, and that employing pharmacological inhibitors of sAC significantly alters cellular energy metabolism. This effect on energy metabolism could influence the interpretation of previous studies employing pharmacological inhibition of sAC. Here, we show that pharmacological inhibition of sAC lowers mitochondrial respiration, induces phosphorylation of the metabolic master switch AMPK, and decreases glycogen stores in cultured astrocytes. In light of this, we discuss the pharmacological challenges of investigating the functional and metabolic roles of sAC in astrocytes.