GABAAR-PPT1 palmitoylation homeostasis controls synaptic transmission and circuitry oscillation

The infantile neuronal ceroid lipofuscinosis, also called CLN1 disease, is a fatal neurodegenerative disease caused by mutations in the CLN1 gene encoding palmitoyl protein thioesterase 1 (PPT1). Identifying the depalmitoylation substrates of PPT1 is crucial for understanding CLN1 disease. In this study, we found that GABA_AR, the critical synaptic protein essential for inhibitory neurotransmission, is a substrate of PPT1. PPT1 depalmitoylates GABA_AR α1 subunit at Cystein-260, while binding to Cystein-165 and -179. Mutations of PPT1 or its GABA_AR α1 subunit binding site enhanced inhibitory synaptic transmission and strengthened oscillations powers but disrupted phase coupling in CA1 region and impaired learning and memory in 1- to 2-months-old PPT1-deficient and Gabra1^em1 mice. Our study highlights the critical role of PPT1 in maintaining GABA_AR palmitoylation homeostasis and reveals a previously unknown molecular pathway in CLN1 diseases induced by PPT1 mutations.