Amyloid pathology disrupts gliotransmitter release in astrocytes

Abstract

Accumulation of amyloid-{beta} peptide (A{beta}), a hallmark of Alzheimers disease (AD), is associated with synchronous hyperactivity and dysregulated Ca2+ signaling in hippocampal astrocytes. However, the consequences of altered Ca2+ signaling on the temporal dynamics of Ca2+ and gliotransmitter release events at astrocytic microdomains are not known. We have developed a detailed biophysical model of microdomain signaling at a single astrocytic process that accurately describes key temporal features of Ca2+ events and Ca2+-mediated kiss-and-run and full fusion exocytosis. Using this model, we ask how aberrant plasma-membrane Ca2+ pumps and mGluR activity, molecular hallmarks of A{beta} toxicity that are also critically involved in Ca2+ signaling, modify astrocytic feedback at a tripartite synapse. We show that AD related molecular pathologies increase the rate and synchrony of Ca2+ and exocytotic events triggered by neuronal activity. Moreover, temporal precision between Ca2+ and release events, a mechanism indispensable for rapid modulation of synaptic transmission by astrocytes, is lost in AD astrocytic processes. Our results provide important evidence on the link between AD-related molecular pathology, dysregulated calcium signaling and gliotransmitter release at an astrocytic process.