RalGDS functions in Ras- and cAMP-mediated growth stimulation.
Thyroid-stimulating hormone stimulates proliferation through both the cAMP-dependent protein kinase and Ras but not through Raf-1 and mitogen-activated and extracellular signal-related kinase kinase. We now report that thyroid-stimulating hormone represses mitogen-activated protein kinase activity and that microinjection of an effector domain mutant Ha-Ras protein, Ras(12V,37G), defective in Raf-1 binding and mitogen-activated protein kinase activation, stimulates DNA synthesis in quiescent and thyroid-stimulating hormone-treated thyrocytes. A yeast two-hybrid screen identified RalGDS as a Ras(12V,37G) binding protein and therefore a potential effector of Ras in these cells. Associations between Ras and RalGDS were observed in extracts prepared from thyroid cells. Microinjection of a mutant RalA(28N) protein thought to sequester RalGDS family members reduced DNA synthesis stimulated by Ras as well as cAMP-mediated DNA synthesis in two cell lines which respond to cAMP with mitogenesis. These results support the idea that RalGDS may be an effector of Ras in cAMP-mediated growth stimulation.
Miller
M J
MJ
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6084, USA.
Prigent
S
S
Kupperman
E
E
Rioux
L
L
Park
S H
SH
Feramisco
J R
JR
White
M A
MA
Rutkowski
J L
JL
Meinkoth
J L
JL
D000242:Cyclic AMP / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism*; D011905:Genes, ras; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008845:Microinjections; D008938:Mitosis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D015398:Signal Transduction; D013972:Thyrotropin / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism*; D020726:ral Guanine Nucleotide Exchange Factor; D020668:rap GTP-Binding Proteins
D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D020726:ral Guanine Nucleotide Exchange Factor; D007334:Insulin-Like Growth Factor I; D013972:Thyrotropin; D000242:Cyclic AMP; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins