c-Jun-N terminal kinase mediated degradation of γ-glutamylcysteine ligase catalytic subunit inhibits GSH recovery after acetaminophen treatment: role in sustaining JNK activation and liver injury

Aims: We confirmed that GCLC protein rapidly decreased at the same time P-JNK increased after APAP treatment. Therefore, our aims were to determine if JNK was directly responsible for decreased causing impaired recovery of GSH and if this was an important factor in determining APAP hepatotoxicity.

Results: Immunoprecipitation of JNK after APAP identified binding to GCLC. Expression of a site directed mutated canonical JNK docking site in GCLC was resistant to degradation and lead to rapid restoration of GSH and inhibited sustained JNK activation. The JNK-resistant GCLC markedly protected against necrosis and ALT elevation. The proteolytic loss of GCLC was abrogated by inhibition of the proteosome, ubiquitination, or calpain.

Innovation: We addressed the aims by preparing mutated Gclc resistant to JNK induced degradation. The results allowed us to identify impaired GSH recovery as an important contributor to early progression of APAP toxicity after the metabolism of APAP and initial GSH depletion had occurred.

Conclusion: Activated JNK interacts directly with GCLC and leads to proteolytic degradation of GCLC. Degradation of GCLC impairs GSH recovery after APAP allowing the continued activation of JNK. Conversely, rapid recovery of GSH inhibits the sustained activation of the MAP Kinase cascade and dampens APAP toxicity by suppressing the continued activation of JNK.