Tyrphostins inhibit follicle-stimulating hormone-mediated functions in cultured rat ovarian granulosa cells.
FSH induces the expression of cholesterol side-chain cleavage cytochrome P450 (P450scc) in rat ovarian granulosa cells. The present study reveals that the tyrphostin AG18, a member of novel protein tyrosine kinase inhibitors, can arrest the FSH-induced synthesis of P450scc with an apparent IC50 of 30 microM. Total inhibition of P450scc expression was achieved at 80 microM AG18. AG18-mediated inhibition of P450scc was also observed when the enzyme was induced by prostaglandin E2, forskolin, or 8-bromo-cAMP. Studies examining functional LH receptors showed that the tyrphostin inhibits the expression of FSH-induced LH receptors. The drug did not affect FSH-induced cAMP accumulation, suggesting that it may interfere with the flow of FSH signal transduction at a site distal intracellular accumulation of cAMP. Control experiments demonstrated that the inhibitory action of AG18 was reversible, did not hamper total protein synthesis in the cells, and did not change the adenine nucleotide (ATP:ADP:AMP) ratio or their levels in the treated cells. A cell-free assay of cAMP-dependent protein kinase showed that the tyrphostin AG18 does not affect this enzyme activity up to concentrations above 200 microM. These results suggest that a putative tyrosine kinase activity is involved in the gonadotropin signal transduction pathway leading to expression of functional genes in ovarian cells.
Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Israel.
S
S
Gomberg-Malool
R
R
Ziv
Y
Y
Re'em
I
I
Posner
A
A
Levitzki
J
J
Orly
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000227:Adenine Nucleotides / Q000378:metabolism; D000818:Animals; D001597:Benzylidene Compounds / Q000494:pharmacology*; D002478:Cells, Cultured; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects / Q000502:physiology*; D009570:Nitriles / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D051381:Rats; D017208:Rats, Wistar; D011974:Receptors, LH / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects; D020032:Tyrphostins
D000227:Adenine Nucleotides; D001597:Benzylidene Compounds; D009570:Nitriles; D047428:Protein Kinase Inhibitors; D011974:Receptors, LH; D020032:Tyrphostins; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D005640:Follicle Stimulating Hormone; D000242:Cyclic AMP; D002786:Cholesterol Side-Chain Cleavage Enzyme; D011505:Protein-Tyrosine Kinases; D015232:Dinoprostone; C060641:tyrphostin A23