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Regulation of lateral mobility and cellular trafficking of the CCK receptor by a partial agonist
Center for Basic Research in Digestive Diseases and Department of Biochemistry and Molecular Biology, Mayo Clinic and Foundation, Rochester, Minnesota 55905 Partial agonists are effective tools for advancing development of highly selective drugs and providing insights into molecular regulation of ce...
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Published in: | American Journal of Physiology: Cell Physiology 1999-03, Vol.276 (3), p.C539-C547 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Center for Basic Research in Digestive Diseases and Department of
Biochemistry and Molecular Biology, Mayo Clinic and Foundation,
Rochester, Minnesota 55905
Partial agonists are effective tools for advancing development
of highly selective drugs and providing insights into molecular regulation of cellular functions. Here, we explore the impact of a
partial agonist on key aspects of cholecystokinin (CCK) receptor regulation, its lateral mobility and cellular trafficking, in native
pancreatic acinar cells and Chinese hamster ovary cells expressing CCK
receptor (CHO-CCKR). We developed and characterized a novel fluorescent
partial agonist,
rhodamine-Gly-[(Nle 28,31 )CCK-26-32]-phenethyl
ester, that binds specifically and with high affinity to CCK receptors.
Such analogs are fully efficacious pancreatic acinar cell secretagogues
without supramaximal inhibition that mobilize intracellular calcium
with little or no increase in phospholipase C (PLC) activity. Despite
minimal phosphorylation of CCK receptors in response to this partial
agonist, receptor trafficking was the same as that observed with full
agonist (CCK). This included normal internalization via
clathrin-dependent endocytosis in CHO-CCKR cells and insulation on the
surface of pancreatic acinar cells. Also, as with CCK-occupied
receptor, fluorescence recovery after photobleaching of partial
agonist-occupied receptor on the acinar cell surface demonstrated a
marked temperature-dependent slowing of its rate of diffusion. This was
similarly associated with resistance to acid-induced dissociation of
ligand. Thus some key molecular regulatory mechanisms for CCK receptor
internalization and insulation may be initiated by cellular signaling
cascades that are not dependent on PLC activation or receptor phosphorylation.
G protein-coupled receptor; receptor mobility; receptor
internalization |
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ISSN: | 0363-6143 1522-1563 |
DOI: | 10.1152/ajpcell.1999.276.3.c539 |