Academic Paper

AbstractAlthough GPR3 plays pivotal roles in both the nervous system and metabolic processes, such as cold-induced thermogenesis, its endogenous ligand remains elusive. Here, by combining structural approach (including cryo-electron microscopy), mass spectrometry analysis, and functional studies, we identify oleic acid (OA) as an endogenous ligand of GPR3. Our study reveals a hydrophobic tunnel within GPR3 that connects the extracellular side of the receptor to the middle of plasma membrane, enabling fatty acids to readily engage the receptor. Functional studies demonstrate that OA triggers downstream Gs signaling, whereas lysophospholipids fail to activate the receptor. Moreover, our research reveals that cold stimulation induces the secretion of OA in mice, subsequently activating Gs/cAMP/PKA signaling in brown adipose tissue. Notably, brown adipose tissues from Gpr3 knockout mice do not respond to OA during cold stimulation, reinforcing the significance of GPR3 in this process. Finally, we propose a “born to be activated and cold to enhance” model for GPR3 activation. Our study provides a starting framework for the understanding of GPR3 signaling in cold-stimulated thermogenesis.

AbstractPlants can adapt to environmental fluctuations through modulating their fatty acids (FAs) dynamically. In this study, an enhanced mass spectrometry approach is utilized to uncover an unexplored landscape of FAs and FA isomers that are critical for cold tolerance in tomato. This technology integrates N‐(4‐aminomethylphenyl) pyridium derivatization of FAs, charge‐tagging Paternò‐Büchi (PB) photochemical reaction to identify carbon–carbon double bond (C═C) positions and reversed‐phase liquid chromatography coupled with tandem mass spectrometry to achieve efficient detection of FAs and their C═C location isomers. Several saturated FAs, unsaturated FAs and their C═C location isomers are revealed to contribute to the cold tolerance of elongated hypocotyl 5 (slhy5) and fatty acid desaturase (slfad) mutant plants. RNA‐sequencing analysis and dual‐luciferase reporter assays further demonstrate that SlHY5 can modulate the expression of SlFAD2 genes under cold stress, regulating FA desaturation. The application of FA isomers to the leaves of slfad mutants partially rescues their cold sensitivity, presenting the practical implications of the study. The study thereby highlights the importance of considering isomeric variations in FAs when investigating plant physiology and stress responses. Furthermore, this methodology sets a valuable precedent for future investigations aimed at unraveling the intricate metabolic networks that govern plant stress adaptation.