Presence of phospholipase C in coated vesicles from bovine brain Dual regulatory effects of GTP‐analogs

Abstract

Bovine brain coated vesicles display free calcium‐dependent phospholipase C activity. Gpp(NH)p and GTPγS inhibited phospholipase C at nanomolar concentrations. Increasing concentrations of Gpp(NH)p and GTPγS reversed the inhibitory effects and stimulated phospholipase C activity. Preincubation of coated vesicles with pertussis toxin blocked the poorly‐hydrolyzable GTP‐analogs' inhibitory effects on phospholipase C. These data indicate that guanine nucleotides exert a dual regulatory control of phospholipase C in coated vesicles and that the inhibitory pathway is mediated by a pertussis toxin‐sensitive G‐protein.

Metabotropic glutamate receptor analogues inhibit p[NH]ppG-stimulated phospholipase C activity in bovine brain coated vesicles: involvement of a pertussis toxin-sensitive G-protein

“…The presence of mGluRs [18,19] and PLC activity [9] in bovine brain coated vesicles has been described, suggesting that these organelles may play a role in the translocation and/or regulation ofthe G-protein-coupled receptors, as other authors have pointed out [20,21]. In this report we present evidence for the coupling of mGluRs, found in bovine brain coated vesicles, to a PLC activity in an inhibitory manner through a pertussis toxin-sensitive Gprotein.…”

“…Pertussis toxin ADP-ribosylation was carried out as described earlier [9]. Coated vesicles were incubated with preactivated pertussis toxin (1 jug pertussis toxin/100 jug protein) or vehicle for 30 min at 30°C in a final volume of 1 ml in 100 mM potassium phosphate buffer, pH 7.4, containing 1 mM EDTA, 2 mM MgCl2, 2 mM NADI, 1 mM ATP, 100 FaM GTP and protease inhibitors (50 ,ug/ml leupeptin and 50 ,ug/ml aprotinin).…”

“…By analogy with the adenylyl cyclase system, it has been suggested that PLC may be regulated via distinct G-proteins, which could activate or inhibit through stimulatory or inhibitory receptors respectively [7]. In fact, a dual regulation of PLC activity by guanine nucleotides has been shown in rat cerebral cortical membranes [8] and bovine brain coated vesicles [9]. Members of the Gq family have been reported to mediate pertussis toxin-insensitive stimulation of PLC [10].…”

Agonist‐Induced Endocytosis of Muscarinic Cholinergic Receptors: Relationship to Stimulated Phosphoinositide Turnover

“…In fact, the issue of whether the internalization of receptors results in their uncoupling from PLC remains to be established. In this context, it should be noted that, in addition to mAChRs, both Gq and PLC are present in subcellular fractions derived from the endocytic pathway (Harden et al, 1985;Martin et al, 1991;Svoboda and Milligan, 1994). Moreover, in these same fractions, the addition of guanine nucleotides can regulate both PLC activity and the affinity with which agonists bind to mAChRs (Harden et al, 1985;Martin et al, 1991).…”

“…In this context, it should be noted that, in addition to mAChRs, both Gq and PLC are present in subcellular fractions derived from the endocytic pathway (Harden et al, 1985;Martin et al, 1991;Svoboda and Milligan, 1994). Moreover, in these same fractions, the addition of guanine nucleotides can regulate both PLC activity and the affinity with which agonists bind to mAChRs (Harden et al, 1985;Martin et al, 1991). In addition, dopamine D 1, dopamine D2, and adenosine A1 receptors have been shown to retain their ability to modulate adenylyl cyclase activity when present in clathrincoated vesicle fractions (Gonzalez-Calero et al, 1990;Ozaki et al, 1994).…”