G<inf>i/o</inf> protein-dependent and -independent actions of pertussis toxin (ptx)

Abstract

Pertussis toxin (PTX) is a typical A-B toxin. The A-protomer (S1 subunit) exhibits ADP-ribosyltransferase activity. The B-oligomer consists of four subunits (S2 to S5) and binds extracellular molecules that allow the toxin to enter the cells. The A-protomer ADP-ribosylates the α subunits of heterotrimeric G i/o proteins, resulting in the receptors being uncoupled from the G i/o proteins. The B-oligomer binds proteins expressed on the cell surface, such as Toll-like receptor 4, and activates an intracellular signal transduction cascade. Thus, PTX modifies cellular responses by at least two different signaling pathways; ADP-ribosylation of the Gα i/o proteins by the A-protomer (G i/o protein-dependent action) and the interaction of the B-oligomer with cell surface proteins (G i/o protein-independent action). © 2011 by the authors; licensee MDPI, Basel, Switzerland.