Cholera toxin inhibits prostaglandin E₁ but not adrenaline‐induced stimulation of GTP hydrolysis in human platelet membranes

The role of GTP in prostaglandin E1 stimulation of adenylate cyclase in platelet membranes

“…Values for cyclic AMP production from platelet membranes stimulated with maximal amounts of PGE1 (10pM) in the presence of GTP were comparable with values reported by Aktories et al (1982) and Stiles & Lefkowitz (1982). Subsequent experiments (Table 1; Figs.…”

Platelet activating factor and U44069 stimulate a GTPase activity in human platelets which is distinct from the guanine nucleotide regulatory proteins, Ns and Ni

“…As has been shown by others (Lester et al, 1982;Aktories et al, 1982), PGE1 stimulated platelet GTPase activity (Table 1). This was clearly a function of Ns, as such a stimulated activity could be blocked by treatment of membranes with cholera toxin (Table 2).…”

cAMP guided his way: a life for G protein-mediated signal transduction and molecular pharmacology—tribute to Karl H. Jakobs

“…Cholera toxin had already been known at the time to persistently activate G s by ADPribosylation (Cassel and Selinger 1977b). Klaus Aktories and Karl H. Jakobs showed that in platelet membranes, where PGE 1 stimulates and adrenaline inhibits adenylyl cyclase, cholera toxin inhibited PGE 1 -stimulated GTP hydrolysis, but had no effect on the adrenaline-stimulated high affinity GTPase activity (Aktories et al 1982a). Again, these data underlined the different nature of G protein-mediated inhibition and stimulation of adenylyl cyclase.…”