An 80-amino acid deletion in the third intracellular loop of a naturally occurring human histamine H3 isoform confers pharmacological differences and constitutive activity.
In this article, we pharmacologically characterized two naturally occurring human histamine H3 receptor (hH3R) isoforms, hH3R(445) and hH3R(365). These abundantly expressed splice variants differ by a deletion of 80 amino acids in the intracellular loop 3. In this report, we show that the hH3R(365) is differentially expressed compared with the hH3R(445) and has a higher affinity and potency for H3R agonists and conversely a lower potency and affinity for H3R inverse agonists. Furthermore, we show a higher constitutive signaling of the hH3R(365) compared with the hH3R(445) in both guanosine-5'-O-(3-[35S]thio) triphosphate binding and cAMP assays, likely explaining the observed differences in hH3R pharmacology of the two isoforms. Because H3R ligands are beneficial in animal models of obesity, epilepsy, and cognitive diseases such as Alzheimer's disease and attention deficit hyperactivity disorder and currently entered clinical trails, these differences in H3R pharmacology of these two isoforms are of great importance for a detailed understanding of the action of H3R ligands.
Bongers
Gerold
G
Leiden/Amsterdam Center for Drug Research, Department of Medicinal Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Krueger
Kathleen M
KM
Miller
Thomas R
TR
Baranowski
John L
JL
Estvander
Brian R
BR
Witte
David G
DG
Strakhova
Marina I
MI
van Meer
Peter
P
Bakker
Remko A
RA
Cowart
Marlon D
MD
Hancock
Arthur A
AA
Esbenshade
Timothy A
TA
Leurs
Rob
R
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000235:genetics; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D011485:Protein Binding; D020033:Protein Isoforms; D011869:Radioligand Assay; D051381:Rats; D018100:Receptors, Histamine H3 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion
D000596:Amino Acids; D008024:Ligands; D020033:Protein Isoforms; D018100:Receptors, Histamine H3; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000242:Cyclic AMP; D019204:GTP-Binding Proteins