Detailed analysis of biased histamine H₄ receptor signalling by JNJ 7777120 analogues.
OBJECTIVE
The histamine H₄ receptor, originally thought to signal merely through Gαi proteins, has recently been shown to also recruit and signal via β-arrestin2. Following the discovery that the reference antagonist indolecarboxamide JNJ 7777120 appears to be a partial agonist in β-arrestin2 recruitment, we have identified additional biased hH₄R ligands that preferentially couple to Gαi or β-arrestin2 proteins. In this study, we explored ligand and receptor regions that are important for biased hH₄R signalling.


METHODS
We evaluated a series of 48 indolecarboxamides with subtle structural differences for their ability to induce hH₄R-mediated Gαi protein signalling or β-arrestin2 recruitment. Subsequently, a Fingerprints for Ligands and Proteins three-dimensional quantitative structure-activity relationship analysis correlated intrinsic activity values with structural ligand requirements. Moreover, a hH₄R homology model was used to identify receptor regions important for biased hH₄R signalling.


RESULTS
One indolecarboxamide (75) with a nitro substituent on position R7 of the aromatic ring displayed an equal preference for the Gαi and β-arrestin2 pathway and was classified as unbiased hH₄R ligand. The other 47 indolecarboxamides were β-arrestin2-biased agonists. Intrinsic activities of the unbiased as well as β-arrestin2-biased indolecarboxamides to induce β-arrestin2 recruitment could be correlated with different ligand features and hH₄R regions.


CONCLUSIONS
Small structural modifications resulted in diverse intrinsic activities for unbiased (75) and β-arrestin2-biased indolecarboxamides. Analysis of ligand and receptor features revealed efficacy hotspots responsible for biased-β-arrestin2 recruitment. This knowledge is useful for the design of hH₄R ligands with biased intrinsic activities and aids our understanding of the mechanism of H₄R activation.
Faculty of Sciences, Amsterdam Institute for Molecules, Medicines and Systems, VU University Amsterdam, The Netherlands.
S
S
Nijmeijer
H F
HF
Vischer
F
F
Sirci
S
S
Schultes
H
H
Engelhardt
C
C
de Graaf
E M
EM
Rosethorne
S J
SJ
Charlton
R
R
Leurs
D019390:Arrestins / Q000378:metabolism*; D045744:Cell Line, Tumor; D015195:Drug Design; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D057809:HEK293 Cells; D006633:Histamine Antagonists / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000737:chemistry / Q000494:pharmacology*; D008024:Ligands; D008958:Models, Molecular; D010879:Piperazines / Q000737:chemistry / Q000494:pharmacology*; D021281:Quantitative Structure-Activity Relationship; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects* / Q000378:metabolism; D011968:Receptors, Histamine / Q000187:drug effects* / Q000378:metabolism; D000074040:Receptors, Histamine H4; D015398:Signal Transduction / Q000187:drug effects*; D000071557:beta-Arrestins
D019390:Arrestins; C418607:HRH4 protein, human; D006633:Histamine Antagonists; D007211:Indoles; D008024:Ligands; D010879:Piperazines; D043562:Receptors, G-Protein-Coupled; D011968:Receptors, Histamine; D000074040:Receptors, Histamine H4; D000071557:beta-Arrestins; C484309:1-((5-chloro-1H-indol-2-yl)carbonyl)-4-methylpiperazine; D019206:GTP-Binding Protein alpha Subunits, Gi-Go
FLAP 3D-QSAR; biased ligands; efficacy; efficacy hotspots; histamine H4 receptor; indolecarboxamides; intrinsic activity; β-arrestin