The Inhibitory G Protein G_i Identified as Pertussis Toxin-Catalyzed ADP-Ribosylation

Abstract

Pertussis toxin (PTX) produced by Bordetella pertussis was first introduced by Ui and his colleagues in research on signal transduction under the name islet-activating protein in 1979, when the mechanism of toxin-induced stimulation of insulin release from pancreatic islets was reported in the rat. The stimulatory effect of PTX in vivo results from the blockage of α 2 -adrenergic receptor-mediated inhibition of insulin release. The receptor-induced inhibition of cAMP formation was also abolished in pancreatic islets isolated from PTX-treated rats, suggesting that the toxin caused uncoupling of adenylyl cyclase inhibition from receptor stimulation. The action of PTX on isolated membranes required a cytosolic factor, nicotinamide adenine dinucleotide (NAD), and the uncoupling induced by PTX was shown to be due to the toxin-catalyzed ADP-ribosylation of a 41-kDa protein with NAD as another substrate. The 41-kDa PTX substrate was soon identified and purified as the α-subunit of the inhibitory G protein that transmits an inhibitory signal from membrane receptors to adenylyl cyclase. After demonstration of the molecular mechanism of PTX, the toxin was widely utilized as a probe for identifying and analyzing major αβγ-trimeric G proteins. Thus, PTX-sensitive G proteins appeared to carry positive and negative signals from many membrane receptors to a variety of effectors other than adenylyl cyclase.

The Endosomal Sorting Complex Required for Transport Pathway Mediates Chemokine Receptor CXCR4-promoted Lysosomal Degradation of the Mammalian Target of Rapamycin Antagonist DEPTOR

“…CXCR4 couples with the pertussis toxin-sensitive G␣ i heterotrimeric G protein (7,53), and as shown in Fig. 10A, CXCL12-induced degradation of DEPTOR was completely blocked in HeLa cells treated with pertussis toxin, indicating that G protein signaling is necessary for CXCR4-promoted DEPTOR degradation.…”

Novel Mechanism of Voltage-Gated N-type (Cav2.2) Calcium Channel Inhibition Revealed through α-Conotoxin Vc1.1 Activation of the GABAB Receptor

“…To elucidate the signaling pathway(s) underlying Vc1.1-dependent inhibition of Ca v 2.2 channels, we first explored the role of PTX-sensitive G i/o G proteins. G i/o G proteins are essential components of GABA inhibition of Ca v 2.2 channels via GABA B Rs (Tedford and Zamponi, 2006;Katada, 2012). PTX ADP ribosylates the Ga i/o subunit, uncoupling it from the receptor (Katada, 2012).…”

“…G i/o G proteins are essential components of GABA inhibition of Ca v 2.2 channels via GABA B Rs (Tedford and Zamponi, 2006;Katada, 2012). PTX ADP ribosylates the Ga i/o subunit, uncoupling it from the receptor (Katada, 2012). To examine the potential role of G i/o G proteins in Vc1.1-dependent inhibition of Ca v 2.2, we treated HEK293 cells coexpressing The depolarizing prepulse to +120 mV relieved GABA inhibition of peak current amplitude but did not significantly affect inhibition by Vc1.1.…”

Effect of pertussis toxin on calcium influx in three contraction models

“…Pertussis toxin (PTX) was first described in 1979 following the report of the PTX-induced stimulation mechanism of insulin release from pancreatic islets in rats (1). The mechanism of PTX action is associated with the inhibition of G protein activation, and thus PTX inhibits the signal transmission from the activated receptor to the effectors that are specific for the G protein-coupled receptor.…”