scholarly journals Purification from bovine liver membranes of a guanine nucleotide-dependent activator of phosphoinositide-specific phospholipase C. Immunologic identification as a novel G-protein alpha subunit.

1990 ◽  
Vol 265 (28) ◽  
pp. 17150-17156 ◽  
Author(s):  
S J Taylor ◽  
J A Smith ◽  
J H Exton
Keyword(s):  
Phospholipase C ◽  
G Protein ◽  
Bovine Liver ◽  
Alpha Subunit ◽  
Guanine Nucleotide ◽  
Liver Membranes ◽  
G Protein Alpha Subunit ◽  
Protein Alpha Subunit

scholarly journals Phospholipase C in Dictyostelium discoideum. Identification of stimulatory and inhibitory surface receptors and G-proteins

1994 ◽  
Vol 297 (1) ◽  
pp. 189-193 ◽  
Author(s):  
A A Bominaar ◽  
P J M Van Haastert
Keyword(s):  
Phospholipase C ◽  
G Protein ◽  
G Proteins ◽  
Alpha Subunit ◽  
Wild Type ◽  
Inhibitory Pathway ◽  
Surface Receptors ◽  
G Protein Alpha Subunit ◽  
Camp Receptor ◽  
Protein Alpha Subunit

A combined biochemical and genetic approach was used to show that phospholipase C in the cellular slime mould Dictyostelium is under dual regulation by the chemoattractant cyclic AMP (cAMP). This dual regulation involves stimulatory and inhibitory surface receptors and G-proteins. In wild-type cells both cAMP and guanosine 5′-[gamma-thio]triphosphate (GTP[S]) stimulated phospholipase C. In contrast, mutant fgd A, lacking the G-protein alpha-subunit G alpha 2, showed no stimulation by either cAMP or GTP[S], indicating that G alpha 2 is the stimulatory G-protein. In mutant fgd C cAMP did not stimulate phospholipase C, but stimulation by GTP[S] was normal, suggesting that the defect in this mutant is upstream of the stimulatory G alpha 2. Inhibition of phospholipase C was achieved in wild-type cells by the partial antagonist 3′-deoxy-3′-aminoadenosine 3′,5′-phosphate (3′NH-cAMP). This inhibition was no longer observed in transformed cell lines lacking either the surface cAMP receptor cAR1 or the G-protein alpha-subunit G alpha 1; in these cells the agonist cAMP still activated phospholipase C. These results indicate that Dictyostelium phospholipase C is regulated via a stimulatory and an inhibitory pathway. The inhibitory pathway is composed of the surface receptor cAR1 and the G-protein G1. The stimulatory pathway consists of an unknown cAMP receptor (possibly the fgd C gene product) and the G-protein G2.

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