The effect of GTP on the aluminum fluoride- and forskolin-activated adenylyl cyclase from human embryonic kidney 293 cells.
GTP has been shown to inhibit AlF4(-)-stimulated, and to activate forskolin-stimulated adenylyl cyclase activity in the presence of Mg2+ in cell membranes from human embryonic kidney 293 cells. The maximal inhibitory response of AlF4(-)-stimulated adenylyl cyclase activity by GTP was not dependent on the concentration of Mg2+, but was so in the case of forskolin-activated activity at all forskolin concentrations assayed. Mn2+ ions stimulated AlF4(-)- or forskolin-activated adenylyl cyclase activity to a greater extent than Mg2+. The inhibition of AlF4(-)-stimulated cyclase by GTP was still observed with Mn2+, but the activation of forskolin-stimulated cyclase by GTP was not. When assayed together, Mn2+ and Mg2+ showed non-additive behaviours with respect to the amount of cyclic AMP formed after AlF4(-)-stimulation of adenylyl cyclase. The temperature dependence of the activation of adenylyl cyclase by forskolin, AlF4- or under basal conditions was observed to be somehow different in the presence of Mn2+ than in the presence of Mg2+ ions. Cholera toxin treatment produced a markedly increased cyclase activity, specially when assayed with AlF4-. In the case of forskolin-activated adenylyl cyclase, UTP and CTP were unable to reproduce the cyclase activation detected with GTP. However, in the case of AlF4(-)-stimulated adenylyl cyclase, UTP was as good as GTP at inhibiting cyclase activity, and CTP virtually eliminated the activation of the cyclase with AlF4-.
Sanchez-Yagüe
J
J
Departamento de Bioquímica y Biología Molecular, Facultad de Biología, Universidad de Salamanca, Spain.
Rodriguez
M C
MC
Llanillo
M
M
Hernandez-Hernandez
A
A
D000262:Adenylyl Cyclases / Q000187:drug effects*; D017607:Aluminum Compounds / Q000494:pharmacology*; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology*; D004789:Enzyme Activation; D005459:Fluorides / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000187:drug effects* / Q000196:embryology / Q000201:enzymology; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology
D017607:Aluminum Compounds; D005576:Colforsin; D008345:Manganese; D006160:Guanosine Triphosphate; D000262:Adenylyl Cyclases; D008274:Magnesium; D005459:Fluorides; C032311:aluminum fluoride