Zebrafish olfactory receptors ORAs differentially detect bile acids and bile salts

The fish olfactory receptor ORA family is orthologous to the mammalian vomeronasal receptors type 1. It consists of six highly conserved chemosensory receptors expected to be essential for survival and communication. We deorphanized the zebrafish ORA family in a heterologous cell system. The six receptors responded specifically to lithocholic acid (LCA) and closely related C24 5β-bile acids/salts. LCA attracted zebrafish as strongly as food in behavioral tests, whereas the less potent cholanic acid elicited weaker attraction, consistent with the in vitro results. The ORA-ligand recognition patterns were probed with site-directed mutagenesis guided by in silico modeling.We revealed the receptors' structure-function relationship underlying their specificity and selectivity for these compounds. Bile acids/salts are putative fish semiochemicals or pheromones sensed by the olfactory system with high specificity. This work identified their receptors and provided the basis for probing the roles of ORAs and bile acids/salts in fish chemosensation. © 2019 Cong et al.1

Modulation of the interaction and organization of Human Dystrophin repeats 11-15 subdomain with Membrane

Dystrophin is essential to skeletal muscle function and confers resistance to the sarcolemma by interacting with cytoskeleton and membrane. In the present work, we characterized the behavior of dystrophin 11–15 (DYS R11–15), five spectrin-like repeats from the central domain of human dystrophin, with lipids. DYS R11–15 displays an amphiphilic character at the liquid/air interface while maintaining its secondary α-helical structure. The interaction of DYS R11–15 with small unilamellar vesicles (SUVs) depends on the lipid nature, which is not the case with large unilamellar vesicles (LUVs). In addition, switching from anionic SUVs to anionic LUVs suggests the lipid packing as a crucial factor for the interaction of protein and lipid. The monolayer model and the modulation of surface pressure aim to mimic the muscle at work (i.e. dynamic changes of muscle membrane during contraction and relaxation) (high and low surface pressure). Strikingly, the lateral pressure modifies the protein organization. Increasing the lateral pressure leads the proteins to be organized in a regular network. Nevertheless, a different protein conformation after its binding to monolayer is revealed by trypsin proteolysis. Label-free quantification by nano-LC/MS/MS allowed identification of the helices in repeats 12 and 13 involved in the interaction with anionic SUVs. These results, combined with our previous studies, indicate that DYS R11–15 constitutes the only part of dystrophin that interacts with anionic as well as zwitterionic lipids and adapts its interaction and organization depending on lipid packing and lipid nature. We provide strong experimental evidence for a physiological role of the central domain of dystrophin in sarcolemma scaffolding through modulation of lipid-protein interactions

L’expérimentation animale reste indispensable (OPINION)

Trop fréquemment, l’expérimentation animale est présentée comme une pratique archaïque. Elle a bien changé. Et 100 % des patients traités le sont grâce aux concepts et techniques développés grâce à elle