Stimulation of Jun N-terminal kinase (JNK) by gonadotropin-releasing hormone in pituitary alpha T3-1 cell line is mediated by protein kinase C, c-Src, and CDC42.
The signaling of ligands operating via heterotrimeric G proteins is mediated by a complex network that involves sequential phosphorylation events. Signaling by the G protein-coupled receptor GnRH was shown to include elevation of Ca2+ and activation of phospholipases, protein kinase C (PKC) and extra-cellular signal-regulated kinase (ERK). In this study, GnRH was shown to activate Jun N-Terminal Kinase (JNK)/SAPK in alpha T3-1 cells in a PKC- and tyrosine kinase-dependent manner. GnRH as well as tumor-promoting agent (TPA) also increased c-Src activity, which peaked at 2 min after GnRH stimulation and was sensitive both to PKC and to tyrosine kinase inhibitors. Coexpression of Csk, which serves as a Src-dominant interfering kinase, and constitutively active forms of Src, together with JNK, confirmed the involvement of c-Src downstream of PKC in the GnRH-JNK pathway. Coexpression of dominant negative and constitutively active forms of CDC42, Rac1, Ras, MEKK1, and MEK1 with JNK indicated that JNK activation by GnRH and TPA is mediated by CDC42 and MEKK1. Ras and MEK1, which are involved in a related mitogen-activated protein kinase (MAPK) pathway, did not affect JNK activation in alpha T3-1 cells. Taken together, our results suggest that GnRH stimulation of JNK activity is mediated by a unique pathway that includes sequential activation of PKC, c-Src, CDC42, and probably also MEKK1.
Levi
N L
NL
Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel.
Hanoch
T
T
Benard
O
O
Rozenblat
M
M
Harris
D
D
Reiss
N
N
Naor
Z
Z
Seger
R
R
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism* / Q000502:physiology; D018797:Cell Cycle Proteins / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic; D014162:Transfection; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins
D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D016755:Proto-Oncogene Proteins c-jun; D011993:Recombinant Fusion Proteins; D007987:Gonadotropin-Releasing Hormone; D016392:Proto-Oncogene Proteins pp60(c-src); D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482578:Map3k1 protein, mouse; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate