Infection By Trichinella Spiralis Activates A Tas2r-mediated Signaling Pathway In Intestinal Tuft Cells

The helminth Trichinella spiralis is one of the most widespread and clinically important parasites in the world,which poses serious health risk to animals and humans.Recent findings indicate that tuft cell,an intestinal epithelial cell type involved in sentience of taste,provides a critical link between the invading worms and subsequent type 2response.Intestinal nematodes and enteric protozoan infection initiate tuft cell hyperplasia,and promote the type 2 immunity by operating the secretion of IL25,which directly acts on ILC2 to induce the IL13 production.ILC2-cell-derived IL-13 in turn contributes to further tuft cell expansion along with goblet cell hyperplasia in a feed-forward loop,ultimately realizing worm expulsion.Nonetheless,how tuft cells are activated by the infection signals and the underlying cellular and molecular mechanisms remain to be fully understood.In this work,we show that a part of tuft subsets express bitter taste receptors.The extracts and excretory-secretory products?E-S?of T.spiralis as well as the bitter compound salicin can activate heterologously expressed mouse Tas2r bitter taste receptors,all of which can also evoke calcium responses from tuft cells in the intestinal organoids and stimulate the release of IL-25 from mouse intestinal villi as well.The extract-induced release of IL-25 can be blocked by a bitter taste receptor inhibitor,allyl isothiocyanate?AITC?.Furthermore,we use gene knockout mice and biochemical inhibitors and other reagents to identify proteins which are involved in cellular downstream signaling pathways.T.spiralis infection activates tuft cell-expressed bitter receptors,which in turn activates the trimeric G protein.We have proved that abolishment of G protein?13 subunit,application of the inhibitors for G protein?o/i,G??subunits and phospholipase C?/?2 dramatically reduces the IL-25release.In addition,knockout of Gng13 significantly reduced T.spiralis infection-induced tuft cell hyperplasia.The free G?1?13 dimer stimulates the phospholipase Plc?/?2 on the cell membrane to generate the second messenger inositol triphosphate?IP3?;Unlike in a taste bud cell,initial tuft cells are found to express the inositol triphosphate receptor type 2?Ip₃r2?to regulate intracellular free calcium ion concentration.Finally,abolition of Trpm5 blocks the Ts-infection-induced tuft cell hyperplasia,while potentiation of Trpm5 by stevioside enhances tuft hyperplasia in vivo.We also find that vesicular transport inhibitor,brefeldin A?BFA?,significantly reduced the IL-25 release from tuft cells in response to Ts extract,indicating that IL-25 is also secreted via vesicles.Taken together,we enunciate that the canonical taste signal transduction components participate in the signaling pathway in a similar but not same manner within tuft cells during the helminths-response process.It provides new ideas for preventing and treating nematode parasitic infections and has important guiding significance for understanding the function of tuft cell and bitter taste receptors in other extraoral tissues.