Neurokinin Receptor

Dysfunction of the neurokinin receptor (NKR) system in the brain is associated with neurological disorders. NKR also referred to as tachykinin receptor belongs to the class of G-protein coupled receptor (GPCR). Three different families have been identified, namely, NK-1, NK-2 and NK-3. Among these three, NK-1 is immensely studied. The NK1R binds preferably to substance P (SP) followed by SP-like hemokinin and endokinin peptides, neurokinin A and neurokinin B. The NK1R is widely distributed throughout the immune and nervous system and regulates the functions of the gastrointestinal tract, respiratory tract, urogenital system, skin, nociceptive transmission and neurogenic inflammation. The NK1R has two isoforms: full-length form and truncated form. 
The full-length NK1R has 407 amino acids, and the truncated form has 311 amino acids differing in the length of the carboxyl terminus. Amongst the NK1R isoforms identified in the human brain, the full-length form appears most common. The truncated form is spread all over peripheral tissues and the central nervous system (CNS)   In cells that express the full-length NK1R, SP caused the augmented calcium level, and increased threonine phosphorylation of protein kinase C δ (PKC δ), ERK-1/2 and activation of NF-?B. The biological responses to SP-mediated through full-length and truncated NK1R are different.  NK1R signaling contributes to the generation of inflammatory mediators leading to neuroinflammation. The NK1R is present in the CNS and peripheral nervous system, with SP as the ligand. However, drugs which modulate the NK1R action are not got into commercial market except for nausea. NK1R antagonists may be considered as a novel therapeutic target for treating CNS disorders.

References

1.Eapen PM, et al. Rev Neurosci. 2019;30(3):233–243.