Vomeronasal receptors are a class of

olfactory receptor Olfactory receptors (ORs), also known as odorant receptors, are chemoreceptors expressed in the cell membranes of olfactory receptor neurons and are responsible for the detection of odorants (for example, compounds that have an odor) which give r ...

s that putatively function as

receptors Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a n ...

for

pheromones A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

. Pheromones have evolved in all animal phyla, to signal sex and dominance status, and are responsible for stereotypical social and sexual behaviour among members of the same species. In mammals, these chemical signals are believed to be detected primarily by the

vomeronasal organ The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory (smell) sense organ located in the soft tissue of the nasal septum, in the nasal cavity just above the roof of the mouth (the hard palate) in various tetrapods. T ...

(VNO), a

chemosensory A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance ( endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemorecep ...

organ located at the base of the

nasal septum The nasal septum () separates the left and right airways of the nasal cavity, dividing the two nostrils. It is depressed by the depressor septi nasi muscle. Structure The fleshy external end of the nasal septum is called the columella or co ...

. The VNO is present in most amphibia, reptiles and non-primate mammals but is absent in birds, adult catarrhine monkeys and apes. An active role for the human VNO in the detection of pheromones is disputed; the VNO is clearly present in the

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal dev ...

but appears to be atrophied or absent in adults. Two distinct families of vomeronasal receptors – which putatively function as pheromone receptors – have been identified in the vomeronasal organ (V1Rs and V2Rs). While all are

G protein-coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...

s (GPCRs), they are distantly related to the receptors of the main olfactory system, highlighting their different role. The V1 receptors share between 50 and 90% sequence identity but have little similarity to other families of G protein-coupled receptors. They appear to be distantly related to the mammalian T2R bitter taste receptors and the rhodopsin-like GPCRs. In rat, the family comprises 30–40 genes. These are expressed in the apical regions of the VNO, in neurons expressing Gi2. Coupling of the receptors to this protein mediates

inositol trisphosphate Inositol trisphosphate or inositol 1,4,5-trisphosphate abbreviated InsP3 or Ins3P or IP3 is an inositol phosphate signaling molecule. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), a phospholipid that is located in the p ...

signaling. A number of human V1 receptor homologues have also been found. The majority of these human sequences are pseudogenes, but an apparently functional receptor has been identified that is expressed in the human

olfactory system The olfactory system, or sense of smell, is the sensory system used for smelling ( olfaction). Olfaction is one of the special senses, that have directly associated specific organs. Most mammals and reptiles have a main olfactory system and an ...

. The V2 receptors are members of GPCR family 3 and have close similarity to the extracellular calcium-sensing receptors. Rodents appear to have around 100 functional V2 receptors and many pseudogenes. These receptors are expressed in the basal regions of VNO, where they couple to G proteins to mediate inositol trisphosphate responses. Homologues have also been identified in fish, and the ligand specificity of one such receptor has been determined: a receptor from goldfish olfactory epithelium has been reported to bind basic amino acids, which are odorants for fish.

Human proteins containing this domain

*V1 ** VN1R1 ** VN1R2 ** VN1R3 ** VN1R5 *V2: None in humans. Vmn2r116 () and Vmn2r26 () are examples in mice.

References

{{G protein-coupled receptors G protein-coupled receptors Protein families Olfactory system

Human proteins containing this domain

See also

References