Introduction of HTR4
5-hydroxytryptamine receptor 4 (HTR4), alternatively called serotonin receptor 4, is a G protein-coupled receptor (GPCR) that is identified as one of the several different receptors for 5-hydroxytryptamine (serotonin). HTR4 is encoded by HTR4 gene in human and is expressed in the alimentary tract, urinary bladder, heart, and adrenal gland as well as the central nervous system (CNS). And particularly in the CNS, HTR4 is found in the putamen, caudate nucleus, nucleus accumbens, globus pallidus, and substantia nigra, and to a lesser extent in the neocortex, raphe, pontine nuclei, and some areas of the thalamus.
|Basic Information of HTR4|
|Protein Name||5-hydroxytryptamine receptor 4|
|Aliases||Serotonin receptor 4, 5-HT-4, 5-HT4|
|Organism||Homo sapiens (Human)|
Function of HTR4 Membrane Protein
HTR4 receptors mediate both excitatory and inhibitory neurotransmission and modulate the release of many neurotransmitters including glutamate, GABA, dopamine, epinephrine/norepinephrine, and acetylcholine, as well as many hormones, including oxytocin, prolactin, vasopressin, and cortisol. HTR4 functions in both the peripheral and central nervous system such as sleep/wake cycle, thermoregulation, food intake, nociception, locomotion, sexual behavior, gastrointestinal motility, blood coagulation, and cardiovascular homeostasis, by modulating the release of various neurotransmitters. The activity of HTR4 is mediated by G proteins that stimulate adenylate cyclase and promote cAMP formation. HTR4 has been implicated in inflammatory hyperalgesia and is supposed to enhance inflammatory pain. The protein p11 was identified as an HTR4-interacting protein. p11 protein may increase HTR4 surface expression in COS-7 cells and facilitates HTR4 signaling. Studies have shown that an HTR4 agonist partially has antidepressant-like effects in rodent models of depression.
Fig.1 Schematic representation of serotonin (5-HT) in the terminal and synapse. (Vinkers, 2010)
Application of HTR4 Membrane Protein in Literature
The results of this article showed that lower 5-HT4 receptor binding in migraine patients was suggestive of higher brain 5-HT levels and indicated that high brain 5-HT levels may represent a trait of the migraine brain or it could be a consequence of migraine attacks.
This study was designed to assess the effect of 5-HT4 receptor activation on the expression of GRK2 and GRK6 in the rat esophagus and distal colon by acute administration of tegaserod and indicated that the basal level of GRK2 and GRK6 expression was sufficient to regulate the desensitization of 5-HT4 receptors in acute drug treatment.
This article concluded that DSP-6952, a novel and orally available 5-HT4 receptor agonist, induced colonic GMCs, enhanced colonic transit, increased defecation without inducing diarrhea, improved drug-induced delay in whole-gut transit, and inhibited visceral hypersensitivity in experimental animals.
The findings of this study identified the mPFC (mouse prefrontal cortex) as the region that mediated the effect of enhanced 5-HT4 receptor activity and CK2 as a modulator of 5-HT4 receptor levels in this brain region that regulated mood-related phenotypes.
Authors of this study suggested that when mPFC-5-HT4Rs were overexpressed and DR-5-HT1ARs were blocked in the DR, hypophagia following stress persisted, suggesting an antidepressant action of early anorexia.
HTR4 Preparation Options
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