Ca2+- or phorbol ester- dependent effect of ATP on a subpopulation of cAMP cell-surface receptors in membranes from D. discoideum. A role for protein kinase C.
D. discoideum cells contain surface receptors for the chemoattractant cAMP which are composed of fast and slowly dissociating binding sites with half-lifes of respectively about 1 s and 15 s (Van Haastert and De Wit, J. Biol. Chem. 259, 13321-13328). In membranes prepared by shearing the cells through a Nucleopore filter, ATP has no effect on cAMP-binding at equilibrium, but the number of slowly dissociating sites is increased about 2-fold by ATP while their apparent affinity and off-rate are not altered by ATP. The effect of ATP is stimulated about 3-fold by Ca2+ with a half maximal effect at 100 microM Ca2+. The tumor promoting phorbol ester, phorbol 12-myristate 13-acetate (PMA), increases this Ca2+-sensitivity of the ATP effect to about 0.2 microM Ca2+. These data suggest that a specific subpopulation of cAMP receptors in membranes from D. discoideum is altered by the action of protein kinase C.
Van Haastert
P J
PJ
De Wit
R J
RJ
Van Lookeren Campagne
M M
MM
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D004023:Dictyostelium; D006150:Guanine Nucleotides / Q000494:pharmacology; D007700:Kinetics; D010704:Phorbols / Q000494:pharmacology*; D011493:Protein Kinase C; D011494:Protein Kinases / Q000378:metabolism*; D011953:Receptors, Cyclic AMP / Q000187:drug effects / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D006150:Guanine Nucleotides; D010704:Phorbols; D011953:Receptors, Cyclic AMP; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium