Ectopic expression of olfactory receptors and associated G-protein subunits in the head integument of the amphihaline migratory fish hilsa Tenualosa ilisha.

The chemosensory nature of the tissue from the dorsal surface of the head (also termed sensory pad; SP) of the amphihaline diadromous fish hilsa Tenualosa ilisha was investigated for odorant receptor (OR), olfactory marker protein (OMP) and G-protein subunits (Gαs-olf, Gαq, Gαo, Gαi3) through immunolocalization and immunoblotting techniques. The immunolocalization of OR, OMP and G-protein subunits showed clear expression of these proteins in the tissues of the SP. Robust expressions of these proteins in the SP were detected with immunoblot analysis. The strong expression of these proteins in the SP indicates that the tissues from this area in riverine T. ilisha may play significant role in chemosensing and signalling through ectopic expression of olfactory receptor proteins which are otherwise reported in olfactory organs in vertebrates. Being migratory in nature, ectopic expression of these receptors in T. ilisha probably helps them to prevent damage to epidermal tissues of the SP, or they may also utilize them as a chemo and mechanosensory tool to optimize chemo-communications during migration.

Inhaled Volatile Molecules-Responsive TRP Channels as Non-Olfactory Receptors.

Generally, odorant molecules are detected by olfactory receptors, which are specialized chemoreceptors expressed in olfactory neurons. Besides odorant molecules, certain volatile molecules can be inhaled through the respiratory tract, often leading to pathophysiological changes in the body. These inhaled molecules mediate cellular signaling through the activation of the Ca2+-permeable transient receptor potential (TRP) channels in peripheral tissues. This review provides a comprehensive overview of TRP channels that are involved in the detection and response to volatile molecules, including hazardous substances, anesthetics, plant-derived compounds, and pheromones. The review aims to shed light on the biological mechanisms underlying the sensing of inhaled volatile molecules. Therefore, this review will contribute to a better understanding of the roles of TRP channels in the response to inhaled molecules, providing insights into their implications for human health and disease.

A pathogen-derived metabolite induces microglial activation via odorant receptors.

Microglia (MG), the principal neuroimmune sentinels in the brain, continuously sense changes in their environment and respond to invading pathogens, toxins, and cellular debris, thereby affecting neuroinflammation. Microbial pathogens produce small metabolites that influence neuroinflammation, but the molecular mechanisms that determine whether pathogen-derived small metabolites affect microglial activation of neuroinflammation remain to be elucidated. We hypothesized that odorant receptors (ORs), the largest subfamily of G protein-coupled receptors, are involved in microglial activation by pathogen-derived small metabolites. We found that MG express high levels of two mouse ORs, Olfr110 and Olfr111, which recognize a pathogenic metabolite, 2-pentylfuran, secreted by Streptococcus pneumoniae. These interactions activate MG to engage in chemotaxis, cytokine production, phagocytosis, and reactive oxygen species generation. These effects were mediated through the Gαs -cyclic adenosine monophosphate-protein kinase A-extracellular signal-regulated kinase and Gßγ -phospholipase C-Ca2+ pathways. Taken together, our results reveal a novel interplay between the pathogen-derived metabolite and ORs, which has major implications for our understanding of microglial activation by pathogen recognition. DATABASE: Model data are available in the PMDB database under the accession number PM0082389.

Olfr603, an orphan olfactory receptor, is expressed in multiple specific embryonic tissues.

BACKGROUND: Olfactory receptors were initially believed to be expressed specifically within the olfactory neurons. However, accumulating genome-scale data has recently demonstrated more extensive expression. There are hundreds of olfactory receptor family members and the realisation of their widespread expression provides an opportunity to reveal new biology. However, existing data is predominantly based on RT-PCR, microarray and RNA-seq approaches and the details of tissue and cell-type specific expression are lacking. RESULTS: As a proof of principle, we selected Olfr603 for expression analysis. We generated an antibody against a non-conserved epitope of Olfr603 and characterised its expression in E8.5-E12.5 mouse embryos using immunohistochemistry. This analysis demonstrated a dynamic pattern of expression in diverse cell types within the developing embryo unrelated to the olfactory system. Expression was detected in migrating neural crest, endothelial precursors and vascular endothelium, endocardial cells, smooth muscle, neuroepithelium and within the ocular tissues. This complex distribution does not conform to any apparent germ layer or tissue origin. CONCLUSIONS: This initial characterisation of Olfr603 expression highlights the potential for a broad role for this receptor in the development of many tissues.