Inhibition of receptor-stimulated guanylyl cyclase by intracellular calcium ions in Dictyostelium cells.
In Dictyostelium discoideum extracellular cAMP stimulates guanylyl cyclase and phospholipase C; the latter enzyme produces Ins(1,4,5)P3 which releases Ca2+ from internal stores. The following data indicate that intracellular Ca2+ ions inhibit guanylyl cyclase activity. 1) In vitro, Ca2+ inhibits guanylyl cyclase with IC50 = 41 nM Ca2+ and Hill-coefficient of 2.1. 2) Extracellular Ca2+ does not affect basal cGMP levels of intact cells. In electro-permeabilized cells, however, cGMP levels are reduced by 85% within 45 s after addition of 10(-6) M Ca2+ to the medium; halfmaximal reduction occurs at 200 nM extracellular Ca2+. 3) Receptor-stimulated activation of guanylyl cyclase in electro-permeabilized cells is also inhibited by extracellular Ca2+ with half-maximal effect at 200 nM Ca2+. 4) In several mutants an inverse correlation exists between receptor-stimulated Ins(1,4,5)P3 production and cGMP formation. We conclude that receptor-stimulated cytosolic Ca2+ elevation is a negative regulator of receptor-stimulated guanylyl cyclase.
Valkema
R
R
Department of Biochemistry, University of Groningen, The Netherlands.
Van Haastert
P J
PJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000502:physiology*; D002463:Cell Membrane Permeability; D000242:Cyclic AMP / Q000494:pharmacology*; D006152:Cyclic GMP / Q000378:metabolism*; D004023:Dictyostelium / Q000187:drug effects / Q000201:enzymology*; D004558:Electric Stimulation; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D015290:Second Messenger Systems
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C022994:cyclic GMP-binding protein; D000242:Cyclic AMP; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D002118:Calcium