3β-hydroxysteroid-Δ24 reductase dampens anti-viral innate immune responses by targeting K27 ubiquitination of MAVS and STING.

The mechanism by which lipid metabolism regulates innate immunity is unknown. Here, we report that the key enzyme in cholesterol synthesis, 3ß-hydroxysteroid-Δ24 reductase (DHCR24), is inhibited by viral infection. DHCR24 deficiency significantly promotes interferon production and interferon-stimulated gene expression. Inhibition of DHCR24 enzyme activity or the addition of the precursor 24-dehydrocholesterol (24-DHC) can augment innate immunity. Mechanistically, DHCR24 interacts with MAVS or STING, and DHCR24 impairs K27-linked ubiquitination of MAVS mediated by TRIM21 and K27-linked ubiquitination of STING mediated by AMFR, blocking the activation of MAVS and STING, respectively. Collectively, DHCR24 plays a negative role in regulating innate immune responses that may be targeted to improve immunity. [ABSTRACT FROM AUTHOR]