Stress granules (SGs) are cytoplasmic biomolecular condensates containing proteins and RNAs in response to stress. Ras-GTPase–activating protein binding protein 1 (G3BP1) is a core SG protein. Caprin-1 and ubiquitin specific peptidase 10 (USP10) interact with G3BP1, facilitating and suppressing SG formation, respectively. The crystal structures of the nuclear transport factor 2-like (NTF2L) domain of G3BP1 in complex with the G3BP1-interacting motif (GIM) of Caprin-1 and USP10 show that both GIMs bind to the same hydrophobic pocket of G3BP1. Moreover, both GIMs suppressed the liquid–liquid phase separation (LLPS) of G3BP1, suggesting that Caprin-1 likely facilitates SG formation via other mechanisms. Thus, we dissected various domains of Caprin-1 and investigated their role in LLPS in vitro and SG formation in cells. The C-terminal domain of Caprin-1 underwent spontaneous LLPS, whereas the N-terminal domain and GIM of Caprin-1 suppressed LLPS of G3BP1. The opposing effect of the N- and C-terminal domains of Caprin-1 on SG formation were demonstrated in cells with or without the endogenous Caprin-1. We propose that the N- and C-terminal domains of Caprin-1 regulate SG formation in a “yin and yang” fashion, mediating the dynamic and reversible assembly of SGs.

Oxidative stress-induced lipid accumulation is mediated by lipid droplets (LDs) homeostasis, which sequester vulnerable unsaturated triglycerides into LDs to prevent further peroxidation. Here we identify the upregulation of lipopolysaccharide-binding protein (LBP) and its trafficking through LDs as a mechanism for modulating LD homeostasis in response to oxidative stress. Our results suggest that LBP induces lipid accumulation by controlling lipid-redox homeostasis through its lipid-capture activity, sorting unsaturated triglycerides into LDs. N-acetyl-L-cysteine treatment reduces LBP-mediated triglycerides accumulation by phospholipid/triglycerides competition and Peroxiredoxin 4, a redox state sensor of LBP that regulates the shuttle of LBP from LDs. Furthermore, chronic stress upregulates LBP expression, leading to insulin resistance and obesity. Our findings contribute to the understanding of the role of LBP in regulating LD homeostasis and against cellular peroxidative injury. These insights could inform the development of redox-based therapies for alleviating oxidative stress-induced metabolic dysfunction.

Proton-detected solid-state NMR in combination with molecular docking and molecular dynamics (MD) simulations allow the study of rhomboid protease inhibition under native-like conditions.

Solid-state nuclear magnetic resonance (ssNMR) methods can probe the motions of membrane proteins in liposomes at the atomic level and propel the understanding of biomolecular processes for which static structures cannot provide a satisfactory description. In this work, we report our study on the fluoride channel Fluc-Ec1 in phospholipid bilayers based on ssNMR and molecular dynamics simulations. Previously unidentified fluoride binding sites in the aqueous vestibules were experimentally verified by ¹⁹ F-detected ssNMR. One of the two fluoride binding sites in the polar track was identified as a water molecule by ¹ H-detected ssNMR. Meanwhile, a dynamic hotspot at loop 1 was observed by comparing the spectra of wild-type Fluc-Ec1 in variant buffer conditions or with its mutants. Therefore, we propose that fluoride conduction in the Fluc channel occurs via a “water-mediated knock-on” permeation mechanism and that loop 1 is a key molecular determinant for channel gating.