Defining STING-sterol interactions with chemoproteomics

Area of Science:

• Immunology
• Molecular Biology
• Cellular Metabolism

Background:

• Stimulator of interferon genes (STING) is a crucial intracellular receptor for detecting cytosolic DNA and cyclic dinucleotides.
• STING regulation is vital to prevent excessive type I interferon responses and autoinflammatory conditions.
• Cholesterol metabolism's role in modulating STING activity is increasingly recognized but not fully understood.

Purpose of the Study:

• To elucidate the molecular mechanisms linking cholesterol homeostasis and STING activity.
• To investigate the impact of cholesterol synthesis modulation on STING function.
• To identify direct interactions between sterols and STING.

Main Methods:

• Genetic manipulation (gain- and loss-of-function systems) including SCAP-SREBP2 and Srebf2 deletion.
• Activity-based protein profiling using sterol-mimetic probes.
• Co-purification assays and subcellular localization studies.

Main Results:

• Increasing SCAP-SREBP2-mediated cholesterol synthesis had minimal effect on STING activity.
• Genetic deletion of Srebf2 enhanced basal and ligand-induced type I interferon responses.
• Direct evidence of STING-sterol binding was observed; VDAC1 was identified as a STING-interacting protein sensitive to sterols. STING localization responded to cellular sterol content changes.

Conclusions:

• STING can function independently of the SCAP-SREBP2 pathway.
• Sterol synthesis in the endoplasmic reticulum influences STING activity.
• Findings support a model where cholesterol recognition amino acid consensus (CARC) motifs mediate cholesterol-dependent STING retention in the ER.