Inhibition of thyrotropin-stimulated DNA synthesis by microinjection of inhibitors of cellular Ras and cyclic AMP-dependent protein kinase.
Microinjection of a dominant interfering mutant of Ras (N17 Ras) caused a significant reduction in thyrotropin (thyroid-stimulating hormone [TSH])-stimulated DNA synthesis in rat thyroid cells. A similar reduction was observed following injection of the heat-stable protein kinase inhibitor of the cyclic AMP-dependent protein kinase. Coinjection of both inhibitors almost completely abolished TSH-induced DNA synthesis. In contrast to TSH, overexpression of cellular Ras protein did not stimulate the expression of a cyclic AMP response element-regulated reporter gene. Similarly, injection of N17 Ras had no effect on TSH-stimulated reporter gene expression. Moreover, overexpression of cellular Ras protein stimulated similar levels of DNA synthesis in the presence or absence of the heat-stable protein kinase inhibitor. Together, these results suggest that in Wistar rat thyroid cells, a full mitogenic response to TSH requires both Ras and cyclic APK-dependent protein kinase.
Kupperman
E
E
Department of Medicine, University of California, San Diego, La Jolla 92093.
Wen
W
W
Meinkoth
J L
JL
D000818:Animals; D002352:Carrier Proteins / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects*; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis*; D005786:Gene Expression Regulation / Q000187:drug effects; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008845:Microinjections; D047428:Protein Kinase Inhibitors; D016283:Proto-Oncogene Proteins p21(ras) / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D051381:Rats; D015398:Signal Transduction; D013961:Thyroid Gland / Q000166:cytology*; D013972:Thyrotropin / Q000037:antagonists & inhibitors*
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D047428:Protein Kinase Inhibitors; C015482:protein kinase modulator; D013972:Thyrotropin; D004247:DNA; D016283:Proto-Oncogene Proteins p21(ras)