Plic-1, a new target in repressing epileptic seizure by regulation of GABA_AR function in patients and a rat model of epilepsy

Dysfunction of γ-aminobutyric acid A (GABA_A) receptors (GABA_ARs) is a prominent factor affecting intractable epilepsy. Plic-1, an ubiquitin-like protein enriched in the inhibitory synapses connecting GABA_ARs and the ubiquitin protease system (UPS), plays a key role in the modification of GABA_AR functions. However, the relationship between Plic-1 and epileptogenesis is not known. In the present study, we aimed to investigate Plic-1 levels in patients with temporal lobe epilepsy, as well as the role of Plic-1 in regulating onset and progression of epilepsy in animal models. We found that Plic-1 expression was significantly decreased in patients with epilepsy as well as pilocarpine- and pentylenetetrazol (PTZ)-induced rat epileptic models. Intrahippocampal injection of the PePα peptide, which disrupts Plic-1 binding to GABA_ARs, significantly shortened the latency of seizure onset, and increased the seizure severity and duration in these two epileptic models. Overexpressed Plic-1 through lentivirus transfection into a PTZ model resulted in a reduction in both seizure severity and generalized tonic–clonic seizure duration. Whole-cell clamp recordings revealed that the PePα peptide decreased miniature inhibitory postsynaptic currents (mIPSCs) whereas overexpressed Plic-1 increased mIPSCs in the pyramidal neurons of the hippocampus. These effects can be blocked by picrotoxin, a GABA_AR inhibitor. Our results indicate that Plic-1 plays an important role in managing epileptic seizures by enhancing seizure inhibition through regulation of GABA_ARs at synaptic sites.