Toll-like receptor mediated inflammation requires FASN-dependent MYD88 palmitoylation.

Toll-like receptor (TLR)/myeloid differentiation primary response protein (MYD88) signaling aggravates sepsis by impairing neutrophil migration to infection sites. However, the role of intracellular fatty acids in TLR/MYD88 signaling is unclear. Here, inhibition of fatty acid synthase by C75 improved neutrophil chemotaxis and increased the survival of mice with sepsis in cecal ligation puncture and lipopolysaccharide-induced septic shock models. C75 specifically blocked TLR/MYD88 signaling in neutrophils. Treatment with GSK2194069 that targets a different domain of fatty acid synthase, did not block TLR signaling or MYD88 palmitoylation. De novo fatty acid synthesis and CD36-mediated exogenous fatty acid incorporation contributed to MYD88 palmitoylation. The binding of IRAK4 to the MYD88 intermediate domain and downstream signal activation required MYD88 palmitoylation at cysteine 113. MYD88 was palmitoylated by ZDHHC6, and ZDHHC6 knockdown decreased MYD88 palmitoylation and TLR/MYD88 activation upon lipopolysaccharide stimulus. Thus, intracellular saturated fatty acid-dependent palmitoylation of MYD88 by ZDHHC6 is a therapeutic target of sepsis.

Distinct roles of FKF1, Gigantea, and Zeitlupe proteins in the regulation of Constans stability in Arabidopsis photoperiodic flowering.

Many plants measure changes in day length to synchronize their flowering time with appropriate seasons for maximum reproductive success. In Arabidopsis, the day-length-dependent regulation of Constans (CO) protein stability is crucial to induce flowering locus T (FT) expression for flowering in long days. The flavin-binding, KELCH repeat, F-box1 (FKF1) protein binds to CO protein specifically in the long-day afternoon and stabilizes it, although the mechanism remains unknown. Here we demonstrated that the FKF1-interacting proteins Gigantea (GI) and Zeitlupe (ZTL) are involved in CO stability regulation. First, our immunoprecipitation-mass spectrometry analysis of FKF1 revealed that FKF1 forms an S-phase kinase-associated protein 1 (Skp1)/Cullin(CUL)/F-box complex through interactions with Arabidopsis Skp1-like 1 (ASK1), ASK2, and CUL1 proteins and mainly interacts with GI protein in vivo. GI interacts with CO directly and indirectly through FKF1. Unexpectedly, the gi mutation increases the CO protein levels in the morning in long days. This gi-dependent destabilization of CO protein was cancelled by the fkf1 mutation. These results suggest that there are other factors likely influenced by both gi and fkf1 mutations that also control CO stability. We found that ZTL, which interacts with GI and FKF1, may be one such factor. ZTL also interacts with CO in vivo. The CO protein profile in the ztl mutant resembles that in the gi mutant, indicating that ZTL activity also may be changed in the gi mutant. Our findings suggest the presence of balanced regulation among FKF1, GI, and ZTL on CO stability regulation for the precise control of flowering time.