A single‐point mutation (Ala280Val) in the third intracellular loop alters the signalling properties of the human histamine H₃ receptor stably expressed in CHO‐K1 cells

Abstract

BACKGROUND AND PURPOSEAn alanine to valine exchange at amino acid position 280 (A280V) in the third intracellular loop of the human histamine H3 receptor was first identified in a patient suffering from Shy-Drager syndrome and later reported as a risk factor for migraine. Here, we have compared the pharmacological and signalling properties of wild-type (hH3RWT) and A280V mutant (hH3RA280V) receptors stably expressed in CHO-K1 cells. EXPERIMENTAL APPROACHThe hH3RA280V cDNA was created by overlapping extension PCR amplification. Receptor expression and affinity were assessed by radioligand (N-α-[methyl- KEY RESULTSBoth receptors were expressed at similar levels with no significant differences in their affinities for H3 receptor ligands. Upon activation the hH3RWT was significantly more efficacious to inhibit forskolin-induced cAMP accumulation and to stimulate [ 35 S]-GTPγS binding, with no difference in pEC50 estimates. The hH3RWT was also more efficacious to stimulate ERK1/2 phosphorylation, but this difference was not significant. The inverse agonist ciproxifan was more efficacious at hH3RWT to reduce [ 35 S]-GTPγS binding but, for both receptors, failed to enhance forskolin-induced cAMP accumulation. CONCLUSIONS AND IMPLICATIONSThe A280V mutation reduces the signalling efficacy of the human H3 receptor. This effect may be relevant to the pathophysiology of disorders associated with the mutation.

The Histamine H3Receptor: Structure, Pharmacology, and Function

“…The rat H 3 R 413 and H 3 R 397 isoforms that lack 32 and 48 aa in ICL3 showed similar efficacy and higher agonist potency for inhibition of forskolin-induced cAMP formation, but for 42/44mitogen-activated protein kinase (MAPK) phosphorylation, the H 3 R 445 coupled considerably better (Drutel et al, 2001). The naturally occurring A280V mutation on ICL3 also modifies the functionality of the hH 3 R 445 to inhibit cAMP accumulation and stimulate 42/44-MAPK phosphorylation (Flores-Clemente et al, 2013).…”

Agonist‐induced activation of histamine H3 receptor signals to extracellular signal‐regulated kinases 1 and 2 through PKC‐, PLD‐, and EGFR‐dependent mechanisms

“…; Flores‐Clemente et al . ). In contrast, other studies give evidence to show that upon activation by an agonist, the H3R exhibits an inhibitory effect on ERK1/2 activation via the activation of PKCα in Mz‐ChA‐1 cells (Francis et al .…”

“…; Flores‐Clemente et al . ). However, the underlying molecular mechanisms regulating the H3R‐mediated ERK1/2 activation remain largely unknown (Bongers et al .…”

Histamine in Migraine and Brain

“…Several isoforms that might have different pharmacological profiles exists, and there is evidence for genetic polymorphism within the human H 3 R. One, where the amino acid 280 (alanine) is substituted to valine, the H 3 R A280V variant, has been considered a risk factor for migraine . The authors of the study suggested that increase histamine release due to increased population of inactive autoreceptors may be the cause, and in a recent study it was shown that the A280V variant actually reduces the signaling efficacy of the H 3 R …”

“…114 The authors of the study suggested that increase histamine release due to increased population of inactive autoreceptors may be the cause, and in a recent study it was shown that the A280V variant actually reduces the signaling efficacy of the H3R. 115 By modifying a side chain of the histamine imidazole molecule, selective and potent receptor agonists have been made, so-called (R)-α-methylhistamine compounds (RAMHs). N α -methylhistamine is a histamine catabolite and an H3R agonist that is about 3 times more active than histamine.…”