TRIM8 Promotes Epileptiform Activity by Destabilizing the Glucocorticoid Receptor NR3C1 and Enhancing AMPA Receptor...

Area of Science:

• Neuroscience
• Molecular Biology
• Epilepsy Research

Background:

• The glucocorticoid receptor NR3C1 has known antiepileptic effects.
• Mechanisms regulating NR3C1 stability during epileptogenesis are not well understood.
• The E3 ubiquitin ligase TRIM8's role in modulating NR3C1 stability and epilepsy is investigated.

Purpose of the Study:

• To determine if TRIM8 regulates neuronal hyperexcitability and epileptic activity by modulating NR3C1.
• To elucidate the molecular mechanisms linking TRIM8, NR3C1, and epileptogenesis.

Main Methods:

• Established in vivo (kainic acid-induced) and in vitro (Mg2+-free media) epilepsy models.
• Utilized gain- and loss-of-function approaches for TRIM8 and NR3C1.
• Employed co-immunoprecipitation, Western blotting, immunofluorescence, and patch-clamp recordings.

Main Results:

• TRIM8 was upregulated in epileptic hippocampi, inversely correlating with NR3C1 levels.
• TRIM8 directly interacted with NR3C1, promoting its polyubiquitination and proteasomal degradation.
• TRIM8-induced NR3C1 reduction enhanced AMPA receptor (AMPAR) phosphorylation and neuronal hyperexcitability; NR3C1 restoration reversed these effects.
• TRIM8 knockdown significantly reduced seizure frequency and severity in vivo.

Conclusions:

• TRIM8 drives epileptiform activity by degrading NR3C1, leading to increased AMPAR phosphorylation and network hyperexcitability.
• The TRIM8-NR3C1-AMPAR axis represents a novel molecular pathway in epileptogenesis.
• This pathway presents a potential therapeutic target for epilepsy treatment.