Agonist and Guanine Nucleotide Regulation of P2Y Purinergic Receptor-Linked Phospholipase C

1990 ◽  
pp. 181-195
Author(s):  
J. L. Boyer ◽  
M. W. Martin ◽  
C. L. Cooper ◽  
G. L. Waldo ◽  
A. J. Morris ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Purinergic Receptor ◽  
Guanine Nucleotide ◽  
Nucleotide Regulation

scholarly journals Guanine nucleotide regulation of phospholipase C activity in permeabilized rabbit neutrophils. Inhibition by pertussis toxin and sensitization to submicromolar calcium concentrations

1986 ◽  
Vol 239 (1) ◽  
pp. 97-102 ◽  
Author(s):  
P G Bradford ◽  
R P Rubin
Keyword(s):  
Phospholipase C ◽  
G Protein ◽  
Pertussis Toxin ◽  
Response Curve ◽  
Regulatory Protein ◽  
Guanine Nucleotide ◽  
Nucleotide Regulation ◽  
Guanine Nucleotide Regulatory Protein ◽  
Stimulation Of

Rabbit neutrophils labelled with [3H]inositol and permeabilized with saponin produced [3H]inositol trisphosphate (InsP3) when incubated with stable analogues of GTP or millimolar concentrations of Ca2+. [3H]InsP3 production elicited by guanosine 5′-[gamma-thio]triphosphate was enhanced by the chemoattractant formylmethionyl-leucyl-phenylalanine and inhibited by pertussis-toxin pretreatment. A pertussis-toxin-sensitive stimulation of [3H]InsP3 concentration was also observed with guanosine 5′-[beta gamma-imido]triphosphate, but not with guanosine 5′-[beta-thio]diphosphate or GTP. Millimolar Ca2+ alone was sufficient to stimulate [3H]InsP3 production; however, in the presence of guanosine 5′-[gamma-thio]triphosphate, the Ca2+ dose-response curve was shifted to submicromolar concentrations. These findings directly confirm the role of a pertussis-toxin-sensitive guanine nucleotide regulatory protein (G protein) in chemoattractant-stimulated phospholipase C activity in rabbit neutrophils. Moreover, the ability of guanine nucleotides to sensitize phospholipase C to physiologically relevant Ca2+ concentrations suggests that the role of the activated G protein may be to enhance the apparent affinity of phospholipase C for Ca2+ and thus to activate the enzyme without an increase in the Ca2+ concentration.

The Phospholipase C Linked P2y-Purinergic Receptor

1990 ◽  
pp. 266-271
Author(s):  
J. L. Boyer ◽  
C. L. Cooper ◽  
M. W. Martin ◽  
G. L. Waldo ◽  
A. J. Morris ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Purinergic Receptor

Guanine nucleotide regulation of the interconversion of the two-state hepatic glucagon receptor system of rat

1988 ◽  
Vol 262 (2) ◽  
pp. 532-542 ◽  
Author(s):  
Russell J. Wyborski ◽  
Edwin M. Horwitz ◽  
W. Terry Jenkins ◽  
Jeffrey S. Mormol ◽  
Ruth S. Gurd
Keyword(s):  
Guanine Nucleotide ◽  
Receptor System ◽  
Glucagon Receptor ◽  
Nucleotide Regulation

Regulation of exocytosis in electrically permeabilized insulin-secreting cells. Evidence for Ca2+ dependent and independent secretion

1987 ◽  
Vol 7 (5) ◽  
pp. 443-454 ◽  
Author(s):  
Claes B. Wollheim ◽  
Susanne Ullrich ◽  
Paolo Meda ◽  
Lucia Vallar
Keyword(s):  
Arachidonic Acid ◽  
Insulin Secretion ◽  
Cyclic Amp ◽  
Phospholipase C ◽  
Guanine Nucleotide ◽  
Rinm5f Cells ◽  
Enzyme Systems ◽  
Enhanced Secretion ◽  
Insulin Secreting Cells ◽  
High Voltage Discharge

The regulation of insulin secretion from RINm5F cells exposed to high voltage discharge has been investigated. Electron microscopy revealed that the overall structure of the cells was preserved after permeabilization. In this preparation insulin release was stimulated by Ca2+ (EC50=2.4 μM). The stable GTP analogue GTPγS enhanced secretion both at intermediate (nano- to micromolar) and vanishingly low (<10 pM) Ca2+ concentrations. At optimal Ca2+ (10 μM) the effect of GTPγS was greatly reduced. We investigated whether the secretory response to GTP analogues was mediated by any of three enzyme systems regulated by GTP-binding proteins, i.e. generation of cyclic AMP by adenylate cyclase, of diacylglycerol by phospholipase C and of arachidonic acid by phospholipase A2. The involvement of these messenger systems could be excluded as (i) cyclic AMP only had minor, Ca2+ dependent effects, (ii) phospholipase C was not activated in the absence of Ca2+ and insulin secretion due to the phorbol ester TPA displayed a different Ca2+ dependency, (iii) arachidonic acid did not elicit Ca2+ independent insulin secretion. These results, taken together with the finding that insulin secretion due to Ca2+ or TPA is attenuated by the inhibitory guanine nucleotide GDPβS, suggest the existence of a regulatory site in exocytosis which is sensitive to guanine nucleotides.

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