Bitter receptor TAS2R138 facilitates lipid droplet degradation in neutrophils during Pseudomonas aeruginosa infection

Bitter receptors function primarily in sensing taste, but may also have other functions, such as detecting pathogenic organisms due to their agile response to foreign objects. The mouse taste receptor type-2 member 138 (TAS2R138) is a member of the G-protein-coupled bitter receptor family, which is not only found in the tongue and nasal cavity, but also widely distributed in other organs, such as the respiratory tract, gut, and lungs. Despite its diverse functions, the role of TAS2R138 in host defense against bacterial infection is largely unknown. Here, we show that TAS2R138 facilitates the degradation of lipid droplets (LDs) in neutrophils during Pseudomonas aeruginosa infection through competitive binding with PPARG (peroxisome proliferator-activated receptor gamma) antagonist: N-(3-oxododecanoyl)-l-homoserine lactone (AHL-12), which coincidently is a virulence-bound signal produced by this bacterium (P. aeruginosa). The released PPARG then migrates from nuclei to the cytoplasm to accelerate the degradation of LDs by binding PLIN2 (perilipin-2). Subsequently, the TAS2R138–AHL-12 complex targets LDs to augment their degradation, and thereby facilitating the clearance of AHL-12 in neutrophils to maintain homeostasis in the local environment. These findings reveal a crucial role for TAS2R138 in neutrophil-mediated host immunity against P. aeruginosa infection.

The Role of Taste Receptor mTAS1R3 in Chemical Communication of Gametes

Fertilization is a multiple step process leading to the fusion of female and male gametes and the formation of a zygote. Besides direct gamete membrane interaction via binding receptors localized on both oocyte and sperm surface, fertilization also involves gamete communication via chemical molecules triggering various signaling pathways. This work focuses on a mouse taste receptor, mTAS1R3, encoded by the Tas1r3 gene, as a potential receptor mediating chemical communication between gametes using the C57BL/6J lab mouse strain. In order to specify the role of mTAS1R3, we aimed to characterize its precise localization in testis and sperm using super resolution microscopy. The testis cryo-section, acrosome-intact sperm released from cauda epididymis and sperm which underwent the acrosome reaction (AR) were evaluated. The mTAS1R3 receptor was detected in late spermatids where the acrosome was being formed and in the acrosomal cap of acrosome intact sperm. AR is triggered in mice during sperm maturation in the female reproductive tract and by passing through the egg surroundings such as cumulus oophorus cells. This AR onset is independent of the extracellular matrix of the oocyte called zona pellucida. After AR, the relocation of mTAS1R3 to the equatorial segment was observed and the receptor remained exposed to the outer surroundings of the female reproductive tract, where its physiological ligand, the amino acid L-glutamate, naturally occurs. Therefore, we targeted the possible interaction in vitro between the mTAS1R3 and L-glutamate as a part of chemical communication between sperm and egg and used an anti-mTAS1R3-specific antibody to block it. We detected that the acrosome reacted spermatozoa showed a chemotactic response in the presence of L-glutamate during and after the AR, and it is likely that mTAS1R3 acted as its mediator.