Histamine H 2 Receptor
| Histamine H 2 Receptor | ||
|---|---|---|
| Properties of human protein | ||
| Mass / length primary structure | 359 AS ; 40.0 kDa | |
| Secondary to quaternary structure | 7TM | |
| Identifier | ||
| Gene name | HRH2 | |
| External IDs | ||
| Occurrence | ||
| Parent taxon | Vertebrates | |
The histamine-H 2 receptor (abbreviated H 2 receptor ) is a protein from the family of histamine receptors that by the body's tissue hormone histamine can be activated. H 2 receptors are involved in the production of gastric juice in a regulatory manner . A stimulation of H 2 -receptors also leads to an acceleration of the heartbeat and to an expansion of small blood vessels. H 2 receptor antagonists ( H 2 antihistamines ), such as. B. cimetidine andRanitidine , inhibit gastric acid production and are used to treat gastric and duodenal ulcers.
biochemistry
genetics
The human H 2 receptor was first cloned in 1991 . It is encoded by a gene on chromosome 5 on the gene locus 5q35. The coding DNA sequence is intron-free .
Protein structure
The human H 2 receptor protein consists of 359 amino acids . As for many other receptors from the family of G protein-coupled receptors , a structure with seven helical transmembrane domains is assumed for the H 2 receptor ( heptahelical receptor ).
Signal transduction
At the molecular level, stimulation of H 2 receptors leads to activation of G s proteins and, as a result, to activation of adenylyl cyclase . This activation of adenylyl cyclase is associated with an accumulation of intracellular cAMP and a release of Ca 2+ from intracellular stores. In addition, H 2 receptors can regulate the activity of genes that play a role in cell proliferation and cell differentiation.
function
The H 2 receptor plays a decisive role in regulating gastric acid production. In addition, this receptor mediates the blood vessel-relaxing effect of histamine and leads to an increase in heart rate.
pharmacology
Antagonists of the H 2 receptor, the H 2 antihistamines, play an important role in the therapy of gastric acid-associated diseases, such as gastric and duodenal ulcers, although they have lost their role in relation to proton pump inhibitors . The H 2 antihistamines include, for example, cimetidine, ranitidine, famotidine and roxatidine .
In addition, H 2 antihistamines (especially cimetidine and ranitidine, which are available for intravenous administration) are used in combination with H 1 antihistamines in the acute therapy of allergic shock and for the prophylaxis of anaphylactic reactions.
H 2 -receptor agonists such as betazole , however, have no therapeutic significance. However, they can be used as diagnostics.
Individual evidence
- ↑ Gantz I, Munzert G, Tashiro T, et al : Molecular cloning of the human histamine H2 receptor . In: Biochem. Biophys. Res. Commun. . 178, No. 3, August 1991, pp. 1386-1392. doi : 10.1016 / 0006-291X (91) 91047-G . PMID 1714721 .
- ^ Del Valle J, Gantz I: Novel insights into histamine H2 receptor biology . In: Am. J. Physiol. . 273, No. 5 Pt 1, November 1997, pp. G987-G996. PMID 9374694 .
- ↑ Allergology Working Group: Acute Therapy ( Memento from December 30, 2009 in the Internet Archive )