Specific Engineered G Protein Coupling to Histamine Receptors Revealed from Cellular Assay Experiments and...

Area of Science:

• Pharmacology
• Molecular Biology
• Biophysics

Background:

• G protein-coupled receptors (GPCRs) are crucial drug targets that mediate cellular responses.
• Histamine receptors H2R and H4R are known GPCRs with incompletely understood G protein coupling.
• Previous studies suggested promiscuous signaling for H2R and selective Gi signaling for H4R.

Purpose of the Study:

• To elucidate the specific G protein coupling profiles of histamine H2R and H4R.
• To investigate the molecular mechanisms underlying their distinct signaling pathways.
• To provide insights into the physiological roles and drug development potential of these receptors.

Main Methods:

• Utilized cellular experimental assays, including mini-G protein recruitment assays in HEK293T cells.
• Employed Gaussian accelerated molecular dynamics (GaMD) simulations to analyze receptor-G protein interactions.
• Combined computational modeling with in vitro experiments to determine coupling specificities.

Main Results:

• H2R demonstrated weaker histamine responses with Gsi and Gsq proteins compared to Gs.
• H4R exhibited selective binding and signaling exclusively through the Gsi protein.
• Molecular dynamics simulations confirmed preferential binding of H2R to Gs and H4R to Gsi, revealing distinct binding orientations.
• Specific residue interactions dictated the orientation of G protein alpha 5 helices within the receptor binding cavities.

Conclusions:

• The study clarifies the distinct G protein coupling preferences of H2R (Gs) and H4R (Gi).
• These findings support the known physiological roles of histamine receptors and highlight the H2R's function in the brain.
• The results underscore the potential for developing H4R-selective drugs.