Unlabelled: The motilin receptor (MTLR) represents a clinically useful pharmacological target, as agonists binding to the MTLR have gastroprokinetic properties. In order to compare the molecular basis for interaction of the MTLR with motilin and with the non-peptide motilin agonist, erythromycin-A (EM-A), the negatively charged E119 located in the third transmembrane (TM3) region was mutated to D (E119D) and Q (E119Q), respectively, and changes in activity of the mutant receptors were verified.
Methods: Each mutant receptor was stably transfected in CHO-cells containing the Ca2+ indicator apo-aequorin. Receptor activation in response to motilin, EM-A and their analogues was assessed by Ca2+-luminescense.
Results: In the E119Q mutant, the Ca2+ response to motilin and EM-A was abolished while in the E119D mutant it was reduced with 62% (motilin) and 81% (EM-A). The pEC50 values were shifted from 9.65+/-0.03 to 7.41+/-0.09 (motilin) and from 6.63+/-0.12 to 4.60+/-0.07 (EM-A). Acetylation of the N-terminal amine group as in [N-acetyl-Phe]1 mot (1-14), decreased the potency 6.3-fold (WT-MTLR) and 148-fold (E119D). Acetylation of EM-A enol ether induced a more pronounced shift in potency: 7943-fold (WT-MTLR) and 1413-fold (E119D).
Conclusion: The comparable loss of affinity of the mutant receptors for motilin and EM-A indicate that these agonists both interact with the TM3 domain of the MTLR. The results with acetylated derivatives support an ionic interaction between E119 of the MTLR with the N+ of the desosamine sugar in EM-A, but not with the N+ of the free amine group in motilin.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1016/j.bcp.2005.06.022 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Differences in motilin receptor desensitization after stimulation with motilin or motilides are due to alternative receptor trafficking.
Biochem Pharmacol
March 2008
Centre for Gastroenterological Research, Catholic University of Leuven, Gasthuisberg O&N 1, bus 701, B-3000 Leuven, Belgium.
Backgrounds & Aims: The motilin receptor (MTLR) is an important therapeutic target for treatment of hypomotility disorders. The negative outcome in clinical trials with the motilin agonist, ABT-229, indicated that desensitization may limit the therapeutic usefulness of motilides. We therefore compared the mechanisms involved in the intracellular trafficking of the MTLR after stimulation with motilin, erythromycin-A (EM-A) or ABT-229.
View Article and Find Full Text PDFExpression of motilin in the hypothalamus and the effect of central erythromycin on gastric motility in diabetic rats.
Neurosci Bull
March 2007
Department of Physiology, School of Medicine, Qingdao University, Qingdao 266071, China.
Objective: To investigate the expression of motilin-immunoreactive neurons in the hypothalamus and the effect of central administration of erythromycin (EM) on the regulation of gastric motility in diabetic rats.
Methods: The motilin immunoreactive neurons in the hypothalamus and the hippocampus were detected by immunohistochemistry with rabbit anti-motilin polyclonal antibody. To measure the gastric motility, force transducers were surgically affixed to the gastric serosa.
Motilin and erythromycin-A share a common binding site in the third transmembrane segment of the motilin receptor.
Biochem Pharmacol
September 2005
Department of Pathophysiology, Centre for Gastroenterological Research, University of Leuven, Gasthuisberg O and N bus 701, B-3000 Leuven, Belgium.
Unlabelled: The motilin receptor (MTLR) represents a clinically useful pharmacological target, as agonists binding to the MTLR have gastroprokinetic properties. In order to compare the molecular basis for interaction of the MTLR with motilin and with the non-peptide motilin agonist, erythromycin-A (EM-A), the negatively charged E119 located in the third transmembrane (TM3) region was mutated to D (E119D) and Q (E119Q), respectively, and changes in activity of the mutant receptors were verified.
Methods: Each mutant receptor was stably transfected in CHO-cells containing the Ca2+ indicator apo-aequorin.
[Effect of motilin receptor agonist-erythromycin on the glucose responsive neurons in hypothalamus of rats].
Zhongguo Ying Yong Sheng Li Xue Za Zhi
August 2005
Medical School of Qingdao University, Qingdao 266021, China.
Aim: In order to explore the mechanism of central motilin-induced feeding behavior, the effects of erythromycin, a motilin receptor agonist, on glucose responsive neurons in hypothalamus were observed.
Methods: Extracellular recordings were made from single neurons in region of lateral hypothalamic area (LHA) and ventromedial hypothalamic nucleus (VMH) in anesthetized rats. On the basis of their responsiveness to intracarotid injection of 0.
Desensitization of the human motilin receptor by motilides.
J Pharmacol Exp Ther
June 2005
Gut Hormone Lab, Center for Gastroenterological Research, Department of Pathophysiology, Katholieke Universiteit Leuven, Belgium.
Tachyphylaxis may have contributed to the failure of the motilide ABT-229 [N-ethyl, N-methyl 4'' deoxy erythromycin (EM)-B enolether] in clinical trials. We compared the desensitizing potency of structurally related motilides [EM-A, EM-A enolether (ME4), N-ethyl, N-methyl EM-A (ME36), EM-B enolether (ME67), N-ethyl, N-methyl EM-A enolether (EM523), ABT-229 and 4'' deoxy EM-A enolether (KOS1326)] in a Chinese hamster ovary (CHO)-K1 cell line expressing the human motilin receptor (MTLR) and in rabbit duodenal segments. CHO-MTLR cells were preincubated with motilides prior to stimulation with motilin.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!