Ectopic Expression of Mammalian Olfactory Receptors

Abstract

Olfactory receptors (ORolfactory receptor (OR)s) are not exclusively detectable in the olfactory epithelium but are ectopically expressed in all other body tissues tested so far such as brain, heart, lung, testis, intestine, and skin. Within these tissues, a specific subset of ORs can be found with some of the ORs being exclusively expressed in only one specific nonolfactory tissue and other OR subsets being more widely distributed throughout different tissues of the body. It is assumed that ectopically expressed ORs, which are nothing but highly specific chemosensors, play a role in the regulation of cell–cell recognition, migration, and pathfinding processes. Additionally, they are attributed to have potential as diagnostical and therapeutical tools as ORs are differentially expressed in pathological tissues (e. g., cancer tissue). Besides the canonical signaling pathways of ORs, as found in the olfactory tissue, alternative pathways are activated in the diverse nonolfactory tissues. In this chapter, the expression and function of ORs outside the olfactory epithelium of the nose will be highlighted.