Abstract
Genistein, a protein tyrosine kinase inhibitor, activates the cystic fibrosis transmembrane conductance regulator (CFTR) in transfected NIH-3T3 fibroblasts that express the CFTR (3T3-CFTR). CFTR activity was assayed by 125I efflux and by patch clamping in the cell-attached mode. Both forskolin and genistein stimulated 125I efflux and activated a 9-10 pS anion channel in 3T3-CFTR cells but failed to activate 125I efflux in mock-transfected NIH-3T3 cells. Genistein, unlike forskolin and 3-isobutyl- 1-methylxanthine, did not increase intracellular adenosine 3',5'-cyclic monophosphate (cAMP) above control levels. This demonstrates that genistein- dependent activation does not involve inhibition of phosphodiesterase activity and suggests that stimulation does not involve a direct activation of protein kinase A. Genistein stimulated 125I efflux to ~50% of the maximal rate with forskolin. Genistein did not increase 125I efflux at saturating forskolin but decreased the concentration of forskolin required for half-maximal stimulation. Orthovanadate (VO4), a phosphotyrosine phosphatase inhibitor, inhibited genistein-induced channel activation with an inhibition constant of approximately 20 μM. These effects suggest that, in addition to activation by protein kinase A, the CFTR is regulated by a tyrosine kinase-dependent pathway.
Original language | English (US) |
---|---|
Journal | American Journal of Physiology - Cell Physiology |
Volume | 268 |
Issue number | 4 37-4 |
State | Published - 1995 |
Externally published | Yes |
Keywords
- 3-isobutyl-1- methylxanthine
- forskolin
- orthovanadate
- phosphodiesterase
- protein kinase A
ASJC Scopus subject areas
- Clinical Biochemistry
- Cell Biology
- Physiology
- Agricultural and Biological Sciences(all)