HM, Depree KM, Parker EM, Graber SG.
Human 5-HT1 receptor subtypes
exhibit distinct G protein coupling behaviors in membranes from Sf9 cells.
Biochemistry 1997 Oct 21;36(42):12930-8
"The G protein coupling behavior
of four human 5-hydroxytryptamine receptor subtypes (5-HT1A, 5-HT1B, 5-HT1D, and
5-HT1E) has been studied in membranes from Sf9 cells expressing the individual
receptors. The 5-HT1A and 5-HT1B receptors exhibited both high- and low-affinity
states for agonist, with the majority of the receptors in a low-affinity state.
Addition of purified G protein subunits to membranes expressing either 5-HT1A
or 5-HT1B receptors shifted the majority of the receptors to a high-affinity state
in the absence, but not in the presence, of guanine nucleotides. The alphai1,
alphai2, alphai3, and alphao subunits were able to shift the receptors to a high-affinity
state with either betagammabrain or betagammaretina while alphat subunits were
inactive regardless of which betagamma preparation was used. A significantly higher
affinity for agonist was observed with both receptors in the presence of alphai3
subunits compared with either alphai2 or alphao subunits, while a significantly
lower concentration of alpha subunits was required for a maximal affinity shift
of 5-HT1A receptors compared with 5-HT1B receptors (EC50 values of 6.4 and 12.
0 nM, respectively). The 5-HT1D and 5-HT1E receptors exhibited only a single affinity
state for agonist. Addition of purified G protein subunits to membranes containing
5-HT1D receptors caused a small increase in affinity for agonist that was only
partially reversed by guanine nucleotides while the addition of purified G protein
subunits to membranes containing 5-HT1E receptors had no affect on agonist binding.
Thus when expressed in an identical membrane environment these four closely related
5-HT1 receptor subtypes exhibit different G protein coupling behaviors."
EM, Izzarelli DG, Lewis-Higgins L, Palmer D, Shapiro RA.
acid differences in the sixth transmembrane domain are partially responsible for
the pharmacological differences between the 5-HT1D beta and 5-HT1E 5-hydroxytryptamine
J Neurochem 1996 Nov;67(5):2096-103
elicits its physiological effects by interacting with a diverse group of receptors.
Two of these receptors, the 5-HT1D beta and the 5-HT1E receptors, are approximately
60% identical in the transmembrane domains that presumably form the ligand binding
site yet have very different pharmacological properties. Analysis of the pharmacological
properties of a series of chimeric 5-HT1D beta/5-HT1E receptors indicates that
sequences in the sixth and seventh transmembrane domains are responsible for the
differential affinity of 5-carboxamidotryptamine for these two receptors. More
detailed analysis shows that two amino acid differences in the sixth transmembrane
domain (Ile333 and Ser334 in the 5-HT1D beta receptor, corresponding to Lys310
and Glu311 in the 5-HT1E receptor) are largely responsible for the differential
affinities of some, but not all, ligands for the 5-HT1D beta and 5-HT1E receptors.
It is likely that these two amino acids subtly determine the overall three-dimensional
structure of the receptor rather than interact directly with individual ligands."
M, Smith C, Herrick-Davis K, Teitler M, Glennon RA.
Binding of tryptamine
analogs at h5-HT1E receptors: a structure-affinity investigation.
Med Chem. 2004 May 15;12(10):2545-52.
for the binding of serotonin (5-HT) analogs at human 5-HT1E receptors were investigated
by examining the affinities of >40 tryptamine-related compounds. No tryptamine
analog was found to bind with substantially higher affinity than 5-HT. The results
indicate that hydrogen bonding plays a key role in the 5-HT1E/receptor interaction.
This finding was supported using quantitative structure-activity analysis (QSAR)
techniques such as comparative molecular field analysis (CoMFA) and the program
D, Nothen MM, Erdmann J, Propping P.
Lack of genetically determined
structural variants of the human serotonin-1E (5-HT1E) receptor protein points
to its evolutionary conservation.
Brain Res Mol Brain Res
"Using single strand conformational analysis, we
screened the complete coding sequence of the serotonin-1E (5-HT1E) receptor gene
for the presence of DNA sequence variation in a sample of 157 unrelated individuals.
We detected only a silent C-->T transition at the third position of codon 177.
The lack of significant mutations leading to structural variants of the human
5-HT1E receptor protein points to a high evolutionary conservation of this receptor
N, Vaysse PJ, Weinshank RL, Branchek TA.
The cloned human 5-HT1E
receptor couples to inhibition and activation of adenylyl cyclase via two distinct
pathways in transfected BS-C-1 cells.
"The pharmacological profile of coupling
of the cloned human serotonin [5-hydroxytryptamine] (5-HT)1E receptors to second
messengers was studied in African green monkey kidney cells (BS-C-1). At low concentrations
(0.1-100 nM), 5-HT inhibited forskolin-stimulated cAMP accumulation (FSCA) by
up to 90% whereas at higher concentrations it potentiated FSCA; potentiation was
dependent on receptor density. Pretreatment of cells with pertussis toxin (PTx)
or cholera toxin (CTx) eliminated agonist-induced inhibition and potentiation
of FSCA, respectively. The potentiation of FSCA was not due to activation of phospholipase
C and/or phospholipase A2 since 5-HT had no effect on inositol phosphate release,
intracellular Ca2+ mobilization or arachidonic acid mobilization; neither was
it affected by pretreatment with the nonselective phospholipase A2 inhibitor,
quinacrine, or by the removal of extracellular Ca2+. The pharmacological profiles
of the 5-HT1E receptor-mediated inhibition and potentiation of FSCA were very
similar, although agonists displayed higher affinity for the former. These results
indicate that the human 5-HT1E receptors can potentially couple, with similar
pharmacological profiles, to multiple effector pathways. However, the potency
and intrinsic activity of the compounds eliciting these responses can differ significantly,
depending on the receptor density and the effector pathway studied." [Abstract]
Bai F, Yin T, Johnstone EM, Su C, Varga G, Little
SP, Nelson DL.
Molecular cloning and pharmacological characterization
of the guinea pig 5-HT1E receptor.
Eur J Pharmacol. 2004
"The human 5-HT(1E) receptor gene was cloned more
than a decade ago. Little is known about its function, and there have been no
reports of its existence in the genome of small laboratory animals. In this study,
attempts to clone the 5-HT(1E) gene from the rat and mouse were unsuccessful.
In fact, a search of the mouse genome database revealed that the 5-HT(1E) receptor
gene is missing from the mouse genome. However, the 5-HT(1E) gene was cloned from
guinea pig genomic DNA and was characterized. The guinea pig 5-HT(1E) receptor
gene encodes a protein of 365 amino acids. It shares 88% (nucleic acid) and 95%
(amino acid) homology with the human receptor. The guinea pig 5-HT(1E) receptor
showed similar pharmacology to the human 5-HT(1E) receptor in radioligand binding
assays. Serotonin (5-hydroxytryptamine, 5-HT) dose-dependently stimulated [35S]GTPgammaS
binding to the guinea pig 5-HT(1E) receptor with an EC(50) of 13.6+/-1.92 nM,
similar to that of the human 5-HT(1E) receptor (13.7+/-1.78 nM). Activation of
the guinea pig 5-HT(1E) receptor was also achieved by ergonovine, alpha-methyl-5-HT,
1-naphthylpiperazine, methysergide, tryptamine, and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane
(DOI). Methiothepin exhibited antagonist activity. Quantitative real-time polymerase
chain reaction (qRT-PCR) analysis showed that 5-HT(1E) mRNA was present in the
guinea pig brain with the greatest abundance in the hippocampus, followed by the
olfactory bulb. Lower levels were detected in the cortex, thalamus, pons, hypothalamus,
midbrain, striatum, and cerebellum. Our current study marks the first identification
of the 5-HT(1E) receptor gene in a commonly used laboratory animal species. This
finding should allow the elucidation of the receptor's role(s) in the complex
coordination of central serotonergic effects." [Abstract]
AT, Landwehrmeyer B, Gustafson EL, Durkin MM, Mengod G, Branchek TA, Hoyer D,
Localization of 5-HT1B, 5-HT1D alpha, 5-HT1E and 5-HT1F
receptor messenger RNA in rodent and primate brain.
"In situ hybridization histochemistry (ISHH)
was used to study the distribution of various 5-HT1 receptor messenger RNAs (mRNA)
in the mammalian nervous system. Since the cDNAs encoding the different 5-HT1
receptors, have not been cloned in one single species, brains of the species appropriate
for the 5-HT1 receptor messenger RNA (mRNA) have been used. Thus, 5-HT1B and 5-HT1D
alpha mRNA were determined in rat and mouse brain, while 5-HT1E and 5-HT1F mRNA
were studied in human (and monkey) and guinea-pig brain, respectively. 5-HT1B
and 5-HT1D alpha hybridization signals were predominantly present in caudate-putamen
and cortical areas; in addition, 5-HT1B mRNA was also detected in hippocampus,
cerebellum and cerebral arteries. In general, the distribution of 5-HT1B mRNA
was characterized by high densities, whereas 5-HT1D alpha mRNA was expressed at
very low levels. Comparison of the localization of the mRNAs to the regional distributions
of the 5-HT1B and 5-HT1D binding sites in rat brain (described in a previous study),
revealed that both receptor subtypes could be putative presynaptic heteroreceptors,
modulating the release of various neurotransmitters in the central nervous system.
The mRNA encoding the recently cloned 5-HT1E receptor, which has low affinity
for the 5-HT1 receptor ligand 5-carboxamidotryptamine (5-CT), was localized in
human brain. It was found to be present in cortical areas, caudate, putamen and
amygdala, areas known to contain 5-CT insensitive 5-HT1 binding sites. The regional
distribution of the 5-HT1F mRNA was determined in guinea-pig brain: high densities
were observed in various cortical areas, the hippocampal formation and claustrum,
which are regions known to contain 5-CT insensitive 5-HT1 or non 5-HT1A/1B/IC/ID
[3H]5-HT binding sites. Altogether, this ISHH study describes the distribution
of mRNAs of recently cloned 5-HT1 receptors in rodent and primate brain and compares
these results to the distribution of the heterogeneous population of 5-HT1 binding
PA, Xie GX, Meuser T, Peroutka SJ.
subtype messenger RNAs in human dorsal root ganglia: a polymerase chain reaction
Neuroscience 1997 Dec;81(3):813-9
serotonin has been shown to play an important role in peripheral pain mechanisms,
the specific subtypes of serotonin receptors involved in pain and hyperalgesia
remain poorly understood. To date, no previous study has attempted to determine
the presence of any serotonin receptor subtype in human dorsal root ganglia. In
this study, the presence of messenger RNA for eight human serotonin receptor subtypes
in lumbar dorsal root ganglia was detected using the method of polymerase chain
reaction. Dorsal root ganglia were excised post mortem from four patients. Oligonucleotide
primers were chosen based on unique regions of complimentary DNA sequence for
eight cloned human serotonin receptor subtypes (i.e. 5-HT1A, 5-HT1D alpha, 5-HT1D
beta, 5-HT1E, 5-HT1F, 5-HT2A, 5-HT2C and 5-HT7). The presence of 5-HT1D alpha,
5-HT1D beta, 5-HT1E, 5-HT1F, 5-HT2A and 5-HT7 receptor subtype messenger RNA was
detected in dorsal root ganglia from three of the four subjects. 5-HT1A receptor
subtype messenger RNA was detected in one of the four subjects. No 5-HT2C receptor
subtype messenger RNA could be detected. Findings from this study may direct further
efforts to determine the role of serotonin receptors in the peripheral nervous
MR, Galvan I, Tailor PT.
Human brainstem serotonin receptors: characterization
and implications for subcortical myoclonus.
"The immediate serotonin (5-HT) precursor, 5-hydroxy-L-tryptophan
(L-5-HTP), is an investigational treatment for myoclonic disorders. Its mechanism
of action in humans is incompletely understood. We measured the density of subtypes
of 5-HT1 and 5-HT2 receptors and the affinity of 5-HT and L-5-HTP in vitro in
the human brainstem and cortex, regions associated with subcortical and cortical
myoclonus, respectively. In the cortex, the rank order of 5-HT receptor subtype
Bmax was 5-HT2A (low-affinity), 5-HT1A, 5-HT uptake sites, 5-HT1D, 5-HT2C, 5-HT1E/F,
and 5-HT2A (high-affinity) sites. In the brainstem, the rank order was 5-HT uptake
sites, 5-HT1D, 5-HT2C, 5-HT1A, and 5-HT2A(L) sites. Specific binding at 5-HT1E/F
and high-affinity 5-HT2A sites was too low for characterization. In competition
studies, 5-HT had high affinity for 5-HT1A and 5-HT2C sites in the brainstem and
cortex, but L-5-HTP was > 1,000-fold less active. These data support the hypothesis
that in humans L-5-HTP stimulates 5-HT receptors in the CNS only after conversion
to 5-HT. They also indicate in the human brainstem a prominence of 5-HT1A sites
and paucity of 5-HT1D, 5-HT1E/F, and 5-HT2A sites, which has implications for
brainstem-mediated myoclonus and response to serotonergic drugs." [Abstract]
FO, Holtgreve-Grez H, Tasken K, Solberg R, Ried T, Gudermann T.
of the gene encoding the 5-HT1E serotonin receptor (S31) (locus HTR1E) to human
Genomics 1994 Aug;22(3):637-40 [Abstract]
JA, Middlemiss DN, Beer MS.
Autoradiographic localization of 5-CT-insensitive
5-HT1-like recognition sites in guinea pig and rat brain.
Neuropharmacology 1996 Feb;35(2):223-9
studies, with [3H]5-HT, were used to investigate the distribution of 5-CT-insensitive
5-HT1-like (5-HT1E/1F) recognition sites in rat and guinea pig brain. For comparison
and control purposes the distribution of the closely related 5-HT1D binding site,
which is abundant in the guinea pig but not the rat, was also investigated, as
well as total specific [3H]5-HT binding. Results from this study confirm the previously
described regional distribution of the 5-HT1D binding site and also revealed a
predominance of 5-CT-insensitive 5-HT1-like 5-HT1E/1F) recognition sites in the
olfactory tubercle, caudate putamen, nucleus accumbens and substantia nigra of
both species. Interestingly 5-CT-insensitive 5-HT1-like (5-HT1E/1F) recognition
sites were particularly dense in the claustrum of the guinea pig, but not the