Analysis of Missense Variants in the Human Histamine Receptor Family Reveals Increased Constitutive Activity of E4106.30x30K Variant in the Histamine H1 Receptor

The Exome Aggregation Consortium has collected the protein-encoding DNA sequences of almost 61,000 unrelated humans. Analysis of this dataset for G protein-coupled receptor (GPCR) proteins (available at GPCRdb) revealed a total of 463 naturally occurring genetic missense variations in the histamine receptor family. In this research, we have analyzed the distribution of these missense variations in the four histamine receptor subtypes concerning structural segments and sites important for GPCR function. Four missense variants R127(3.52x52)H, R139(34.57x57)H, R409(6.29x29)H, and E410(6.30x30)K, were selected for the histamine H-1 receptor (H1R) that were hypothesized to affect receptor activity by interfering with the interaction pattern of the highly conserved D(E)RY motif, the so-called ionic lock. The E410(6.30x30)K missense variant displays higher constitutive activity in G protein signaling as compared to wild-type H1R, whereas the opposite was observed for R127(3.52x52)H, R139(34.57x57)H, and R409(6.29x29)H. The E410(6.30x30)K missense variant displays a higher affinity for the endogenous agonist histamine than wild-type H1R, whereas antagonist affinity was not affected. These data support the hypothesis that the E410(6.30x30)K mutation shifts the equilibrium towards active conformations. The study of these selected missense variants gives additional insight into the structural basis of H1R activation and, moreover, highlights that missense variants can result in pharmacologically different behavior as compared to wild-type receptors and should consequently be considered in the drug discovery process.

Automated summary

The Exome Aggregation Consortium has collected the protein-encoding DNA sequences of almost 61,000 unrelated humans and identified 463 naturally occurring genetic missense variations in the histamine receptor family. The research analyzed the distribution of these variations in the four histamine receptor subtypes and selected four missense variants for further study regarding their impact on receptor activity.