A cloned CCK-A receptor transduces multiple signals in response to full and partial agonists.
Chinese hamster ovary (CHO) cells, stably transfected with the cloned rat CCK-A receptor, were used to study signal transduction events initiated by cholecystokinin octapeptide (CCK-8) and the partial agonist JMV-180. In single CHO-CCK-A cells loaded with fura-2, superfusion of CCK-8 (10 pM-1 nM) resulted in an increase in intracellular Ca2+ concentration ([Ca2+]i). At CCK-8 concentrations < 100 pM, the signal consisted of [Ca2+]i oscillations. At higher concentrations, CCK-8 induced a typical biphasic response consisting of a large peak followed by a lower sustained plateau. Superfusion of JMV-180 also resulted in an increase in [Ca2+]i; in contrast to acinar cells this increase did not consist exclusively of [Ca2+]i oscillations. Both CCK-8 and JMV-180 increased polyphosphoinositide hydrolysis, although JMV-180 stimulated formation of only 10% as much [3H]inositol phosphates. [Ca2+]i signals stimulated by both CCK-8 and JMV-180 were blocked by the aminosteroid U-73122. CCK-8 (1-10 nM) increased formation of adenosine 3',5'-cyclic monophosphate (cAMP) and release of arachidonic acid in CHO-CCK cells. These increases were not mimicked by JMV-180 (10 microM). Furthermore, no cAMP formation or arachidonate release could be detected when cells were incubated with both JMV-180 and CCK-8. These data indicate that in CHO-CCK-A cells, unlike acinar cells, both CCK-8 and JMV-180 increase [Ca2+]i by similar mechanisms. However, the CCK-A receptor can differentially recognize and then activate discrete transduction pathways on binding of these two agonists.
Yule
D I
DI
Department of Physiology, University of Michigan, Ann Arbor 48109.
Tseng
M J
MJ
Williams
J A
JA
Logdson
C D
CD
D000818:Animals; D016466:CHO Cells; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002766:Cholecystokinin / Q000494:pharmacology*; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary; D004963:Estrenes / Q000494:pharmacology; D007700:Kinetics; D016133:Polymerase Chain Reaction; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D011949:Receptors, Cholecystokinin / Q000187:drug effects / Q000502:physiology*; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D012844:Sincalide / Q000031:analogs & derivatives / Q000494:pharmacology*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors; D014162:Transfection; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
D018076:DNA, Complementary; D004963:Estrenes; D011760:Pyrrolidinones; D011949:Receptors, Cholecystokinin; D011994:Recombinant Proteins; D013729:Terpenes; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C058451:JMV 180; D000001:Calcimycin; D019284:Thapsigargin; D002766:Cholecystokinin; D010738:Type C Phospholipases; D000252:Calcium-Transporting ATPases; D012844:Sincalide; D002118:Calcium