Differential coupling of the human cannabinoid receptors hCB1R and hCB2R to the G-protein Gαi2β1γ2

Nickl, Kathrin; Gardner, Eric E.; Geiger, Sarah S.; Heilmann, Jörg; Seifert, Roland

doi:10.1016/j.neulet.2008.09.078

Cited by 10 publications

(4 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2, F and G). This is in good agreement with ratios determined for other G i/o -coupled receptors in Sf9 cell membranes, for example the hH 4 R (Schneider et al, 2009), human cannabinoid receptors CB 1 and CB 2 (Nickl et al, 2008), and the human formyl peptide receptor (Wenzel- Seifert et al, 1998). Table 1).…”

Section: Immunological Detection Of Recombinant Proteinssupporting

confidence: 86%

No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H₃ Receptor Coupled to Defined G_i/G_o Protein Heterotrimers

Schnell¹,

Burleigh²,

Trick³

et al. 2009

J Pharmacol Exp Ther

Self Cite

View full text Add to dashboard Cite

Numerous structurally diverse ligands were developed to target the human histamine H 3 receptor (hH 3 R), a presynaptic G i /G ocoupled auto-and heteroreceptor. Proxyfan was identified to be functionally selective, with different efficacies toward G i /G odependent hH 3 R signaling pathways. However, the underlying molecular mechanism of functional selectivity of proxyfan is still unclear. In the current study, we investigated the role of different G␣ i/o proteins in hH 3 R signaling, using a baculovirus/Sf9 cell expression system. We tested the hypothesis that ligandspecific coupling differences to defined G i /G o -heterotrimers are responsible for functional selectivity of proxyfan at hH 3 R. In Sf9 membranes, full-length hH 3 R (445 amino acids) was expressed in combination with an excess of different mammalian G proteins (G␣ i1 , G␣ i2 , G␣ i3 , or G␣ o1 and ␤ 1 ␥ 2 dimers, respectively). In addition, we constructed the fusion proteins hH 3 R-G␣ i2 and hH 3 R-G␣ o1 to ensure clearly defined receptor/G protein stoichiometries. Steady-state GTPase experiments were performed to directly measure the impact of each G protein on hH 3 R signal transduction. The hH 3 R coupled similarly to all G proteins. We also observed similar ligand-independent or constitutive activity. Proxyfan and various other imidazole-containing ligands, including full agonists, partial agonists, and inverse agonists, showed very similar pharmacological profiles not influenced by the type of G protein coexpressed. Selected ligands, examined in membranes expressing the fusion proteins hH 3 R-G␣ i2 and hH 3 R-G␣ o1 (plus ␤ 1 ␥ 2 dimers), yielded very similar results. Collectively, our data indicate that hH 3 R couples similarly to different G␣ i/o -subunits and that ligand-specific active receptor conformations, resulting in G protein-coupling preferences, do not exist for proxyfan or other imidazole compounds investigated.

show abstract

Section: Immunological Detection Of Recombinant Proteinssupporting

confidence: 86%

No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H₃ Receptor Coupled to Defined G_i/G_o Protein Heterotrimers

Schnell¹,

Burleigh²,

Trick³

et al. 2009

J Pharmacol Exp Ther

Self Cite

View full text Add to dashboard Cite

show abstract

“…We preformed a sequence alignment between mouse CB 1 and mouse CB 2 , and highlighted in red the sequence motifs located in the intracellular loops that may account for the differential interactions with G proteins and found that these regions exhibit a much diminished 29% similarity (Figure S3). In agreement with this reduced amino acid similarity in intracellular sequences, a recent study showed that the binding of the same agonist to either CB 1 or CB 2 receptors leads to differential activation of G-proteins [33]. Another possible explanation of how the same agonist engaging either CB 1 or CB 2 receptors might differentially activate a signal transduction mechanism is based on studies that were obtained with “ligand-assisted protein structure” (LAPS) analysis [34], [35].…”

Section: Discussionmentioning

confidence: 85%

The Expression Level of CB1 and CB2 Receptors Determines Their Efficacy at Inducing Apoptosis in Astrocytomas

et al. 2010

View full text Add to dashboard Cite

BackgroundCannabinoids represent unique compounds for treating tumors, including astrocytomas. Whether CB1 and CB2 receptors mediate this therapeutic effect is unclear.Principal FindingsWe generated astrocytoma subclones that express set levels of CB1 and CB2, and found that cannabinoids induce apoptosis only in cells expressing low levels of receptors that couple to ERK1/2. In contrast, cannabinoids do not induce apoptosis in cells expressing high levels of receptors because these now also couple to the prosurvival signal AKT. Remarkably, cannabinoids applied at high concentration induce apoptosis in all subclones independently of CB1, CB2 and AKT, but still through a mechanism involving ERK1/2.SignificanceThe high expression level of CB1 and CB2 receptors commonly found in malignant astrocytomas precludes the use of cannabinoids as therapeutics, unless AKT is concomitantly inhibited, or cannabinoids are applied at concentrations that bypass CB1 and CB2 receptors, yet still activate ERK1/2.

show abstract

“…In the late 1980s and early 1990s, the concept of constitutive GPCR activity was developed. This concept assumes that receptors exist in an inactive (R) and an active (R*) state and that they isomerize between Nickl et al (2008) Most studies regarding the effects of monovalent ions were performed with G i /G o -coupled receptors. It should be emphasised that the majority of relevant studies were performed with membrane preparations, i.e.…”

Section: Introductionmentioning

confidence: 99%

Modulation of GPCRs by monovalent cations and anions

Straßer

Wittmann

Schneider

et al. 2014

Naunyn-Schmiedeberg's Arch Pharmacol

Self Cite

View full text Add to dashboard Cite

The recent resolution of G-protein-coupled receptor (GPCR) structures in complex with Na(+) bound to an allosteric modulatory site has renewed interest of the regulation of GPCRs by ions. Here, we summarise key data on ion modulation of GPCRs, obtained in pharmacological, crystallographic, mutagenesis and molecular modelling studies. We show that ion modulation is a highly complex process, involving not only cations but also, rather neglected until now, anions. Pharmacotherapeutic and toxicological aspects are discussed. We provide a mathematical framework for the analysis of ion effects. Finally, we discuss open questions in the field and future research directions. Most importantly, the in vivo relevance of the modulation of GPCR function by monovalent ions must be clarified.

show abstract

Differential coupling of the human cannabinoid receptors hCB1R and hCB2R to the G-protein Gαi2β1γ2

Cited by 10 publications

References 15 publications

No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H₃ Receptor Coupled to Defined G_i/G_o Protein Heterotrimers

No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H₃ Receptor Coupled to Defined G_i/G_o Protein Heterotrimers

The Expression Level of CB1 and CB2 Receptors Determines Their Efficacy at Inducing Apoptosis in Astrocytomas

Modulation of GPCRs by monovalent cations and anions

Contact Info

Product

Resources

About

Differential coupling of the human cannabinoid receptors hCB1R and hCB2R to the G-protein Gαi2β1γ2

Cited by 10 publications

References 15 publications

No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H3 Receptor Coupled to Defined Gi/Go Protein Heterotrimers

No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H3 Receptor Coupled to Defined Gi/Go Protein Heterotrimers

The Expression Level of CB1 and CB2 Receptors Determines Their Efficacy at Inducing Apoptosis in Astrocytomas

Modulation of GPCRs by monovalent cations and anions

Contact Info

Product

Resources

About

No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H₃ Receptor Coupled to Defined G_i/G_o Protein Heterotrimers

No Evidence for Functional Selectivity of Proxyfan at the Human Histamine H₃ Receptor Coupled to Defined G_i/G_o Protein Heterotrimers