Forskolin binding to intact S49 lymphoma cells

Area of Science:

• Biochemistry
• Cell Biology
• Pharmacology

Background:

• Forskolin and hormones are known to synergistically activate adenylate cyclase.
• This suggests hormones might influence forskolin's binding to the enzyme.

Purpose of the Study:

• To investigate whether hormones, specifically epinephrine and isoproterenol, stimulate forskolin binding to adenylate cyclase.
• To determine the characteristics and requirements of this hormone-stimulated forskolin binding.

Main Methods:

• Utilized intact wild type S49 cultured lymphoma cells.
• Employed a filtration technique with 40 nM [3H]-forskolin to measure binding.
• Tested the effects of varying epinephrine and isoproterenol concentrations, stereospecificity, and cytochalasin B inhibition.

Main Results:

• Forskolin binding increased with epinephrine or isoproterenol concentration.
• Hormone-dependent binding was stereospecific (l-epinephrine) and absent in cyc- variant cells.
• Binding was not inhibited by cytochalasin B, indicating association with the adenylate cyclase system and a functional Gs unit.

Conclusions:

• Hormone stimulation specifically enhances forskolin binding to the adenylate cyclase system, requiring a functional Gs protein.
• There is not a direct one-to-one correlation between the extent of forskolin binding and adenylate cyclase activation by epinephrine.