Pertussis toxin reverses the inhibition of the adenylyl cyclase system by khellin in HeLa cells.

Khellin, a furochromone structurally related to furocoumarins, is a phototherapeutic agent used against psoriasis and vitiligo. This paper reports that pretreatment of HeLa cells with pertussis toxin reverses both the inhibition of NaF-stimulated adenylyl cyclase activity and the stimulation of GTPase by khellin alone and plus UVA light, as previously reported. Our results demonstrate, for the first time, that khellin is able to elicit an intracellular response by Gi alpha protein.