Inverse agonism: the classic concept of GPCRs revisited [Review]

Sato, Junichiro; Makita, Noriko; Iiri, Taroh

doi:10.1507/endocrj.ej16-0084

Cited by 31 publications

(23 citation statements)

References 56 publications

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“…In this context it is important to note that clofibric acid, the active metabolite of clofibrate [141] acts as an inverse agonist on the human TAS1R3 receptor [129,130]. Due to the pronounced reproductive phenotype of clofibrate treated males expressing the humanized hmTas1r3 on a gustducin null background [129], one might suggest that taste receptors show a high frequency of spontaneous activation [142] and that such a constitutive activity of taste receptors in the male reproductive system is sufficient to fulfil their physiological function.…”

Section: Genetic Deletion Of Taste Receptors In Mouse and Its Impamentioning

confidence: 99%

Taste Receptors: New Players in Sperm Biology

Luddi

Governini

Wilmskötter

et al. 2019

IJMS

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Taste receptors were first described as sensory receptors located on the tongue, where they are expressed in small clusters of specialized epithelial cells. However, more studies were published in recent years pointing to an expression of these proteins not only in the oral cavity but throughout the body and thus to a physiological role beyond the tongue. The recent observation that taste receptors and components of the coupled taste transduction cascade are also expressed during the different phases of spermatogenesis as well as in mature spermatozoa from mouse to humans and the overlap between the ligand spectrum of taste receptors with compounds in the male and female reproductive organs makes it reasonable to assume that sperm “taste” these different cues in their natural microenvironments. This assumption is assisted by the recent observations of a reproductive phenotype of different mouse lines carrying a targeted deletion of a taste receptor gene as well as the finding of a significant correlation between human male infertility and some polymorphisms in taste receptors genes. In this review, we depict recent findings on the role of taste receptors in male fertility, especially focusing on their possible involvement in mechanisms underlying spermatogenesis and post testicular sperm maturation. We also highlight the impact of genetic deletions of taste receptors, as well as their polymorphisms on male reproduction.

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Section: Genetic Deletion Of Taste Receptors In Mouse and Its Impamentioning

confidence: 99%

Taste Receptors: New Players in Sperm Biology

Luddi

Governini

Wilmskötter

et al. 2019

IJMS

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“…AM630 as a CB2 protean ligand binds and stabilizes inactive receptor conformations with high affinity [ 12 ] and, therefore, shifts the activity equilibrium towards inactivity. In a system with high basal activity, corroborated by the inability of CB2 agonists to elicit additional activity, this will lead to pronounced inverse agonism, as seen in type CA cells [ 31 ].…”

Section: Discussionmentioning

confidence: 99%

“…Different CB2 agonists might have varying dynamics and signaling bias that is dependent on CB2 phosphorylation that could originate from PKA activation downstream of cAMP production by FSK [ 29 , 30 , 31 ]. Because the highly potent and cAMP biased CB1/CB2 agonist CP55,940 is regularly used as a reference ligand to establish experimental protocols [ 13 , 21 ], with regard to this, previously reported agonist differences have to be interpreted accordingly.…”

Section: Discussionmentioning

confidence: 99%

Monitoring Cannabinoid CB2 -Receptor Mediated cAMP Dynamics by FRET-Based Live Cell Imaging

Mensching

Rading

Nikolaev

et al. 2020

IJMS

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G-protein coupled cannabinoid CB2 receptor signaling and function is primarily mediated by its inhibitory effect on adenylate cyclase. The visualization and monitoring of agonist dependent dynamic 3′,5′-cyclic adenosine monophosphate (cAMP) signaling at the single cell level is still missing for CB2 receptors. This paper presents an application of a live cell imaging while using a Förster resonance energy transfer (FRET)-based biosensor, Epac1-camps, for quantification of cAMP. We established HEK293 cells stably co-expressing human CB2 and Epac1-camps and quantified cAMP responses upon Forskolin pre-stimulation, followed by treatment with the CB2 ligands JWH-133, HU308, β-caryophyllene, or 2-arachidonoylglycerol. We could identify cells showing either an agonist dependent CB2-response as expected, cells displaying no response, and cells with constitutive receptor activity. In Epac1-CB2-HEK293 responder cells, the terpenoid β-caryophyllene significantly modified the cAMP response through CB2. For all of the tested ligands, a relatively high proportion of cells with constitutively active CB2 receptors was identified. Our method enabled the visualization of intracellular dynamic cAMP responses to the stimuli at single cell level, providing insights into the nature of heterologous CB2 expression systems that contributes to the understanding of Gαi-mediated G-Protein coupled receptor (GPCR) signaling in living cells and opens up possibilities for future investigations of endogenous CB2 responses.

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“…The equilibrium between both receptor states is shifted to the active side by (partial) agonists and/or interaction with G proteins. The inactive state, however, is stabilized by (partial) inverse agonists Sato et al 2016). The degree of constitutive activity depends on the intrinsic tendency of the receptor protein to occur in the active state.…”

Section: Influence Of Monovalent Ions On Hh 3 R Functionmentioning

confidence: 99%

Pharmacological Characterization of Human Histamine Receptors and Histamine Receptor Mutants in the Sf9 Cell Expression System

Schneider

Seifert

2017

Handbook of Experimental Pharmacology

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A large problem of histamine receptor research is data heterogeneity. Various experimental approaches, the complex signaling pathways of mammalian cells, and the use of different species orthologues render it difficult to compare and interpret the published results. Thus, the four human histamine receptor subtypes were analyzed side-by-side in the Sf9 insect cell expression system, using radioligand binding assays as well as functional readouts proximal to the receptor activation event (steady-state GTPase assays and [S]GTPγS assays). The human HR was co-expressed with the regulators of G protein signaling RGS4 or GAIP, which unmasked a productive interaction between hHR and insect cell Gα. By contrast, functional expression of the hHR required the generation of an hHR-Gsα fusion protein to ensure close proximity of G protein and receptor. Fusion of hHR to the long (Gsα) or short (Gsα) splice variant of Gα resulted in comparable constitutive hHR activity, although both G protein variants show different GDP affinities. Medicinal chemistry studies revealed profound species differences between hHR/hHR and their guinea pig orthologues gpHR/gpHR. The causes for these differences were analyzed by molecular modeling in combination with mutational studies. Co-expression of the hHR with Gα, Gα, Gα, and Gα in Sf9 cells revealed high constitutive activity and comparable interaction efficiency with all G protein isoforms. A comparison of various cations (Li, Na, K) and anions (Cl, Br, I) revealed that anions with large radii most efficiently stabilize the inactive hHR state. Potential sodium binding sites in the hHR protein were analyzed by expressing specific hHR mutants in Sf9 cells. In contrast to the hHR, the hHR preferentially couples to co-expressed Gα in Sf9 cells. Its high constitutive activity is resistant to NaCl or GTPγS. The hHR shows structural instability and adopts a G protein-independent high-affinity state. A detailed characterization of affinity and activity of a series of hHR antagonists/inverse agonists allowed first conclusions about structure/activity relationships for inverse agonists at hHR. In summary, the Sf9 cell system permitted a successful side-by-side comparison of all four human histamine receptor subtypes. This chapter summarizes the results of pharmacological as well as medicinal chemistry/molecular modeling approaches and demonstrates that these data are not only important for a deeper understanding of HR pharmacology, but also have significant implications for the molecular pharmacology of GPCRs in general.

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Inverse agonism: the classic concept of GPCRs revisited [Review]

Cited by 31 publications

References 56 publications

Taste Receptors: New Players in Sperm Biology

Taste Receptors: New Players in Sperm Biology

Monitoring Cannabinoid CB2 -Receptor Mediated cAMP Dynamics by FRET-Based Live Cell Imaging

Pharmacological Characterization of Human Histamine Receptors and Histamine Receptor Mutants in the Sf9 Cell Expression System

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