Irreversible inhibition of forskolin interactions with type I adenylyl cyclase by a 6-isothiocyanate derivative of forskolin.
Forskolin (Fsk) has been demonstrated to interact directly with the enzyme adenylyl cyclase (EC 4.6.1.1) in diverse tissues. However, the ability of Fsk to bind to and activate adenylyl cyclase varies depending on the tissue being studied. Different adenylyl cyclase subtypes have been cloned and expressed in a recombinant Sf9 expression system. This provides an opportunity to study the effects of chemically reactive derivatives of Fsk on individual adenylyl cyclase subtypes in the absence of Gs alpha. Reaction of type I adenylyl cyclase with an isothiocyanate derivative of Fsk (6-[[N-(2-isothiocyanatoethyl)amino]carbonyl]forskolin) causes irreversible inhibition of Fsk binding with an IC50 of 300 nM and irreversible inhibition of Fsk activation with an IC50 of 10 microM, suggesting that there are two sites of 6-[[N-(2-isothiocyanatoethyl)amino]carbonyl]forskolin interaction. These studies establish the usefulness of the isothiocyanate derivative of Fsk in localizing the site(s) of Fsk interaction with type I adenylyl cyclase.
Sutkowski
E M
EM
Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA. sutkowski@a1.fdacb.cber.fda.gov
Robbins
J D
JD
Tang
W J
WJ
Seamon
K B
KB
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000345:Affinity Labels; D000818:Animals; D001665:Binding Sites; D005576:Colforsin / Q000031:analogs & derivatives / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D017879:Isothiocyanates / Q000494:pharmacology*; D018411:Spodoptera
D000345:Affinity Labels; D017879:Isothiocyanates; D005576:Colforsin; D000262:Adenylyl Cyclases; D004229:Dithiothreitol