Distinct mechanisms drive sequential internalization and degradation of GABAARs during global ischemia and reperfusion injury
Joshua D. Garcia,
Sarah E. Wolfe,
Amber R. Stewart,
Erika Tiemeier,
Sara E. Gookin,
Mayra Bueno Guerrero,
Nidia Quillinan,
Katharine R. Smith
Affiliations
Joshua D. Garcia
Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
Sarah E. Wolfe
Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
Amber R. Stewart
Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
Erika Tiemeier
Department of Anesthesiology, Neuronal Injury Program, University of Colorado School of Medicine, Anschutz Medical Campus, 12801 East 17th Avenue, Aurora, CO 80045, USA
Sara E. Gookin
Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
Mayra Bueno Guerrero
Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA
Nidia Quillinan
Department of Anesthesiology, Neuronal Injury Program, University of Colorado School of Medicine, Anschutz Medical Campus, 12801 East 17th Avenue, Aurora, CO 80045, USA
Katharine R. Smith
Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 East 19th Avenue, Aurora, CO 80045, USA; Corresponding author
Summary: Synaptic inhibition is critical for controlling neuronal excitability and function. During global cerebral ischemia (GCI), inhibitory synapses are rapidly eliminated, causing hyper-excitability which contributes to cell-death and the pathophysiology of disease. Sequential disassembly of inhibitory synapses begins within minutes of ischemia onset: GABAARs are rapidly trafficked away from the synapse, the gephyrin scaffold is removed, followed by loss of the presynaptic terminal. GABAARs are endocytosed during GCI, but how this process accompanies synapse disassembly remains unclear. Here, we define the precise trafficking itinerary of GABAARs during the initial stages of GCI, placing them in the context of rapid synapse elimination. Ischemia-induced GABAAR internalization quickly follows their initial dispersal from the synapse, and is controlled by PP1α signaling. During reperfusion injury, GABAARs are then trafficked to lysosomes for degradation, leading to permanent removal of synaptic GABAARs and contributing to the profound reduction in synaptic inhibition observed hours following ischemia onset.
