![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Digestive Diseases Branch, National Institute of Diabetes and
Digestive and Kidney Diseases, National Institutes of Health, Bethesda,
Maryland 20892 (T.T., T.K., W.H., R.V.B., R.T.J.), and
National
Institute on Deafness and Other Communication Disorders, National
Institutes of Health, Rockville, Maryland 20850 (M.A.A., G.S.K.,
J.F.B.)
The relationship between receptor number and agonist-induced
intracellular responses has been well studied in receptors coupled to
adenylate cyclase; however, for receptors coupled to phospholipase C
(PLC), very little is known about the effect of receptor number on
receptor-mediated processes. To explore this issue, we investigated the
effect of the number of receptors for gastrin-releasing peptide (GRP)
on ligand affinity and on the ability to activate intracellular messengers [PLC, tyrosine phosphorylation of p125 focal adhesion kinase (p125FAK)] and cause receptor modulation
(internalization, desensitization, down-regulation) and ligand
degradation. Three BALB 3T3 cell lines were made that stably expressed
the gastrin-releasing peptide receptor (GRP-R) with receptor numbers
varying by 280-fold (GRP-R-Low, GRP-R-Med, and GRP-R-Hi). Each cell
line had the same affinity for agonist. The efficacy for bombesin to
increase [3H]inositol phosphates but not tyrosine
phosphorylation of p125FAK correlated well with receptor
number. In contrast, the EC50 value for
[3H]inositol phosphate generation for bombesin was the
same in each cell line. Receptor number did not alter internalization.
In the absence of protease inhibitors, there was an inverse correlation between receptor number and receptor down-regulation and
desensitization. However, with protease inhibitors present, GRP-R-Med
and GRP-R-Hi down-regulated significantly less than the GRP-R-Low.
Similarly, GRP-R-Low desensitized significantly more than GRP-R-Med or
GRP-R-Hi. GRP-R-Hi caused significantly greater ligand degradation than GRP-R-Low, and protease inhibitors completely inhibited degradation by
GRP-R-Low and inhibited degradation by 70% for GRP-R-Hi. In conclusion, we show that for the PLC-coupled GRP-R, receptor number had
little or no effect on binding affinity, potency for activating PLC,
tyrosine phosphorylation of p125FAK, or extent of receptor
internalization. In contrast, receptor number had an effect on ligand
degradation, down-regulation, desensitization, and efficacy of PLC
activation without altering the efficacy of tyrosine phosphorylation of
p125FAK. These results demonstrate that the effect of
receptor number differs for the different functions mediated by the GRP
receptor and differs from that reported for adenylate cyclase-coupled
receptors such as receptors mediating the action of adrenergic agents,
secretin, and opioids.
This article has been cited by other articles:
|
|
 |
|
  R. T. Jensen, J. F. Battey, E. R. Spindel, and R. V. Benya International Union of Pharmacology. LXVIII. Mammalian Bombesin Receptors: Nomenclature, Distribution, Pharmacology, Signaling, and Functions in Normal and Disease States Pharmacol. Rev., March 1, 2008; 60(1): 1 - 42. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Gudermann and S. Roelle Calcium-dependent growth regulation of small cell lung cancer cells by neuropeptides Endocr. Relat. Cancer, December 1, 2006; 13(4): 1069 - 1084. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Schuhmacher, H. Zhang, J. Doll, H. R. Macke, R. Matys, H. Hauser, M. Henze, U. Haberkorn, and M. Eisenhut GRP Receptor-Targeted PET of a Rat Pancreas Carcinoma Xenograft in Nude Mice with a 68Ga-Labeled Bombesin(6-14) Analog J. Nucl. Med., April 1, 2005; 46(4): 691 - 699. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P.-W. Chen and G. S. Kroog Alterations in Receptor Expression or Agonist Concentration Change the Pathways Gastrin-Releasing Peptide Receptor Uses to Regulate Extracellular Signal-Regulated Kinase Mol. Pharmacol., December 1, 2004; 66(6): 1625 - 1634. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. A. Ally, K. L. Ives, E. Traube, I. Eltounsi, P.-W. Chen, P. J. Cahill, J. F. Battey, M. R. Hellmich, and G. S. Kroog Agonist- and Protein Kinase C-Induced Phosphorylation Have Similar Functional Consequences for Gastrin-Releasing Peptide Receptor Signaling via Gq Mol. Pharmacol., October 1, 2003; 64(4): 890 - 904. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Lin, X. Jian, Z. Lin, G. S. Kroog, S. Mantey, R. T. Jensen, J. Battey, and J. Northup Two Amino Acids in the Sixth Transmembrane Segment of the Mouse Gastrin-Releasing Peptide Receptor Are Important for Receptor Activation J. Pharmacol. Exp. Ther., September 1, 2000; 294(3): 1053 - 1062. [Abstract] [Full Text]
|
|
|
|
|
|
R. R. Ryan, H. C. Weber, S. A. Mantey, W. Hou, M. E. Hilburger, T. K. Pradhan, D. H. Coy, and R. T. Jensen Pharmacology and Intracellular Signaling Mechanisms of the Native Human Orphan Receptor BRS-3 in Lung Cancer Cells J. Pharmacol. Exp. Ther., October 1, 1998; 287(1): 366 - 380. [Abstract] [Full Text]
|
|
|
|
 |
|
 R. R. Ryan, H. C. Weber, W. Hou, E. Sainz, S. A. Mantey, J. F. Battey, D. H. Coy, and R. T. Jensen Ability of Various Bombesin Receptor Agonists and Antagonists to Alter Intracellular Signaling of the Human Orphan Receptor BRS-3 J. Biol. Chem., May 29, 1998; 273(22): 13613 - 13624. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. C. MacKinnon, C. Waters, D. Jodrell, C. Haslett, and T. Sethi Bombesin and Substance P Analogues Differentially Regulate G-protein Coupling to the Bombesin Receptor. DIRECT EVIDENCE FOR BIASED AGONISM J. Biol. Chem., July 20, 2001; 276(30): 28083 - 28091. [Abstract] [Full Text] [PDF]
|
|
 |
 |
 |
|
 |
 |
 |
