Olfactory Marker Protein Expression Is an Indicator of Olfactory Receptor-Associated Events in Non-Olfactory Tissues

Abstract

Olfactory receptor (OR)-associated events are mediated by well-conserved components in the olfactory epithelium, including olfactory G-protein (Golf), adenylate cyclase III (ACIII), and olfactory marker protein (OMP). The expression of ORs has recently been observed in non-olfactory tissues where they are involved in monitoring extracellular chemical cues. The large number of OR genes and their sequence similarities illustrate the need to find an effective and simple way to detect non-olfactory OR-associated events. In addition, expression profiles and physiological functions of ORs in non-olfactory tissues are largely unknown. To overcome limitations associated with using OR as a target protein, this study used OMP with Golf and ACIII as targets to screen for potential OR-mediated sensing systems in non-olfactory tissues. Here, we show using western blotting, real-time PCR, and single as well as double immunoassays that ORs and OR-associated proteins are co-expressed in diverse tissues. The results of immunohistochemical analyses showed OMP (+) cells in mouse heart and in the following cells using the corresponding marker proteins c-kit, keratin 14, calcitonin, and GFAP in mouse tissues: interstitial cells of Cajal of the bladder, medullary thymic epithelial cells of the thymus, parafollicular cells of the thyroid, and Leydig cells of the testis. The expression of ORs in OMP (+) tissues was analyzed using a refined microarray analysis and validated with RT-PCR and real-time PCR. Three ORs (olfr544, olfr558, and olfr1386) were expressed in the OMP (+) cells of the bladder and thyroid as shown using a co-immunostaining method. Together, these results suggest that OMP is involved in the OR-mediated signal transduction cascade with olfactory canonical signaling components between the nervous and endocrine systems. The results further demonstrate that OMP immunohistochemical analysis is a useful tool for identifying expression of ORs, suggesting OMP expression is an indicator of potential OR-mediated chemoreception in non-olfactory systems.

The Odorant Receptor-Dependent Role of Olfactory Marker Protein in Olfactory Receptor Neurons

“…Thus, by tuning noise and response kinetics, OMP is a key regulator of ORN physiology. It will be interesting to investigate whether OMP might also play a similar role in other tissues, given its recently reported broader expression pattern (Kang et al, 2015).…”

“…Olfactory marker protein (OMP), a protein thought to be exclusively expressed in mature ORNs (Margolis, 1972), has been shown to be involved in olfactory kinetics. Interestingly, OMP was recently found to be expressed in other nonolfactory tissues, often with ORs and AC3 (Kang et al, 2015). Electro-olfactograms from OMP knock-out (KO) mice have slower onset and decay kinetics compared with wild type (WT; Buiakova et al, 1996).…”

Hedgehog signaling regulates ciliary localization of mouse odorant receptors

“…However, some dead newborn Smo fl/fl pups had milk in the stomach, indicating that the mortality was not necessarily due to inability to suckle. An alternative possibility was that the neonatal mortality was dependent on a lack of Smo signaling in OMP-positive cells other than OSNs, e.g., vomeronasal sensory neurons or OMP-positive nonolfactory cells (18,19). Because of the neonatal mortality, we analyzed mice at embryonic day 18.5 (E18.5).…”

Olfactory marker protein regulates prolactin secretion and production by modulating Ca2+ and TRH signaling in lactotrophs

“…Recent studies have reported that OMP and ORs are expressed in non-olfactory tissues, including the pancreas, colon, bladder, and thyroid gland 15,18,[28][29][30] . However, there have been no previous investigations on the expression and physiological functions of OMP in the pituitary gland.…”

“…However, it is not known whether OMP function is conserved across tissues. Recent studies have suggested a link between OMP and the endocrine system, especially in neuroendocrine neoplasia and hormone secretion [15][16][17][18] . However, to date, there have been no studies investigating the role of OMP in the functioning of the pituitary gland, which is considered the master regulator of the neuroendocrine system.…”