Differential roles of PKC isoforms (PKCs) and Ca2+in GnRH and phorbol 12-myristate 13-acetate (PMA) stimulation of p38MAPK phosphorylation in immortalized gonadotrope cells.
We examined the role of PKCs and Ca2+in GnRH-stimulated p38MAPK phosphorylation in the gonadotrope derived αT3-1 and LβT2 cell lines. GnRH induced a slow and rapid increase in p38MAPK phosphorylation in αT3-1 and LβT2 cells respectively, while PMA gave a slow response. The use of dominant negatives for PKCs and peptide inhibitors for the receptors for activated C kinase (RACKs), has revealed differential role for PKCα, PKCβII, PKCδ and PKCε in p38MAPK phosphorylation in a ligand-and cell context-dependent manner. The paradoxical findings that PKCs activated by GnRH and PMA play a differential role in p38MAPK phosphorylation may be explained by differential localization of the PKCs. Basal, GnRH- and PMA- stimulation of p38MAPK phosphorylation in αT3-1 cells is mediated by Ca2+influx via voltage-gated Ca2+channels and Ca2+mobilization, while in the differentiated LβT2 gonadotrope cells it is mediated only by Ca2+mobilization. p38MAPK resides in the cell membrane and is relocated to the nucleus by GnRH (∼5 min). Thus, we have identified the PKCs and the Ca2+pools involved in GnRH stimulated p38MAPK phosphorylation.
Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel.
Shany
S
Mugami
Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel.
Shani
S
Kravchook
Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel.
Liat
L
Rahamim-Ben Navi
Department of Biological Regulation, The Weizmann Institute of Science, Rehovot 76100, Israel.
Rony
R
Seger
Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel. Electronic address: zvin@tauex.tau.ac.il.
Zvi
Z
Naor
D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002461:Cell Line, Transformed; D052681:Gonadotrophs / Q000187:drug effects* / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D015759:Ionomycin / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008954:Models, Biological; D010455:Peptides / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism
D007527:Isoenzymes; D010455:Peptides; D010703:Phorbol Esters; D047428:Protein Kinase Inhibitors; C119222:phorbol-12-myristate; D007987:Gonadotropin-Releasing Hormone; D000001:Calcimycin; D015759:Ionomycin; D019061:src-Family Kinases; D011493:Protein Kinase C; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium
GnRH; Gonadotropes; MAPKs; PKCα; PKCβII; PKCδ; PKCε; p38; αT3-1 and LβT2 cells