Kyotorphin receptor (KTR)

The Kyotorphin receptor is a G protein-coupled receptor (GPCR) that serves as the primary target for the endogenous analgesic dipeptide kyotorphin (L-tyrosyl-L-arginine) [1, 2]. It is predominantly expressed in the central nervous system, particularly in brain regions involved in pain processing such as the periaqueductal gray, midbrain, and medulla oblongata [1, 9]. Upon activation, the receptor couples with Gi proteins to stimulate phospholipase C (PLC) and inhibit adenylyl cyclase, leading to an increase in intracellular calcium and the subsequent release of Met-enkephalin [1, 12]. This indirect mechanism produces potent, naloxone-reversible analgesia without the dipeptide binding directly to opioid receptors [2, 6]. Beyond its role in nociception, the receptor is implicated in neuroprotection and the pathophysiology of Alzheimer's disease, where decreased kyotorphin levels have been observed in patient cerebrospinal fluid [2, 10]. Although its pharmacological properties and signaling pathways are well-documented, the specific gene encoding the kyotorphin receptor has not yet been definitively cloned [2].

Other names

KTP receptorKyotorphin-sensitive receptorKTPr

Agonist binding activates Gi-protein signaling, stimulating phospholipase C and inhibiting adenylyl cyclase, which triggers the release of endogenous Met-enkephalin to produce indirect opioid-mediated analgesia.