JNK regulates GABAAR expression at the cell surface via the receptor clustering protein GIT1 (ArfGAP1)

Abstract

GABAA-type receptors (GABAARs) mediate fast and tonic inhibition and are essential for maintaining excitatory/inhibitory balance in neural circuits. Disrupted GABAergic signaling leads to maladaptive changes associated with neuropsychiatric disorders, yet the mechanisms that regulate GABAAR surface availability remain incompletely understood. We previously identified that the stress-activated kinase JNK1 drives anxiety-like behaviours in mice suggesting a potential link between stress signalling and GABAergic regulation. Here, we show that genetic deletion or inhibition of JNK1 increases surface expression of {beta}3-containing GABAARs at extrasynaptic sites and at excitatory synapses where they may participate in shunting inhibition. We identify the signalling scaffold GIT1 as a direct JNK1 substrate, phosphorylated at S371, and find that GIT1 accumulates in dendritic spines in Jnk1-/- neurons or following JNK inhibition, whereas the phosphomimetic GIT1-S371D is excluded. Moreover, GIT1 is required for JNK-dependent regulation of {beta}3-GABAAR trafficking. Accordingly, neurons from Jnk1-/- mice exhibit increased spontaneous inhibitory postsynaptic potentials and enhanced tonic inhibition. These results reveal a JNK1-GIT1 signalling axis that suppresses GABAAR stability and inhibitory tone, providing a mechanism by which the stress-activated JNK pathway modulates synaptic and extrasynaptic inhibition.