Once pertussis toxin enters human cells, it disrupts normal cellular signaling by ADP-ribosylation of the Gi protein, a critical component of the G protein-coupled receptor (GPCR) system. This modification inhibits the Gi protein's function, leading to increased levels of intracellular cyclic AMP (cAMP). Elevated cAMP affects various cellular responses, including immune cell function, contributing to the characteristic symptoms of pertussis.
