Sumoylation of RORγt regulates T_H17 differentiation and thymocyte development

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• RORγt (Retinoid-related Orphan Receptor gamma t) is essential for T_H17 cell differentiation, a key player in autoimmune conditions such as experimental autoimmune encephalomyelitis (EAE).
• RORγt also plays a role in thymocyte development and lymph node formation.
• Post-translational modifications, like sumoylation, are increasingly recognized as critical regulators of protein function.

Purpose of the Study:

• To investigate the role of sumoylation in regulating RORγt function.
• To identify the specific E3 ligase and site of RORγt sumoylation.
• To elucidate the molecular mechanism by which sumoylation affects RORγt activity and its downstream consequences.

Main Methods:

• Utilized mouse models with genetic modifications (e.g., loss of Sumo3, mutation of RORγt at K31).
• Assessed T_H17 cell differentiation, thymic cell populations (ISPs), and EAE progression.
• Investigated protein-protein interactions using techniques like co-immunoprecipitation to study RORγt, PIAS4, KAT2A, and SRC1 interactions.

Main Results:

• Loss of Sumo3 impaired T_H17 differentiation and thymic ISP progression.
• RORγt sumoylation at lysine 31 (K31) by PIAS4 was identified as crucial.
• RORγt K31R mutant mice exhibited defective T_H17 differentiation, resistance to EAE, thymic ISP accumulation, and Peyer's patch deficiency.
• Sumoylation at RORγt-K31 recruits KAT2A, stabilizing SRC1 binding and enhancing RORγt transcriptional activity.

Conclusions:

• Sumoylation is a critical regulatory mechanism for RORγt function.
• The sumoylation of RORγt-K31 by PIAS4 is essential for T_H17 cell differentiation and immune homeostasis.
• This pathway presents potential therapeutic targets for T_H17-mediated autoimmune diseases.