Proline-rich tyrosine kinase 2 mediates gonadotropin-releasing hormone signaling to a specific extracellularly regulated kinase-sensitive transcriptional locus in the luteinizing hormone beta-subunit gene.
G protein-coupled receptor regulation of gene transcription primarily occurs through the phosphorylation of transcription factors by MAPKs. This requires transduction of an activating signal via scaffold proteins that can ultimately determine the outcome by binding signaling kinases and adapter proteins with effects on the target transcription factor and locus of activation. By investigating these mechanisms, we have elucidated how pituitary gonadotrope cells decode an input GnRH signal into coherent transcriptional output from the LH beta-subunit gene promoter. We show that GnRH activates c-Src and multiple members of the MAPK family, c-Jun NH2-terminal kinase 1/2, p38MAPK, and ERK1/2. Using dominant-negative point mutations and chemical inhibitors, we identified that calcium-dependent proline-rich tyrosine kinase 2 specifically acts as a scaffold for a focal adhesion/cytoskeleton-dependent complex comprised of c-Src, Grb2, and mSos that translocates an ERK-activating signal to the nucleus. The locus of action of ERK was specifically mapped to early growth response-1 (Egr-1) DNA binding sites within the LH beta-subunit gene proximal promoter, which was also activated by p38MAPK, but not c-Jun NH2-terminal kinase 1/2. Egr-1 was confirmed as the transcription factor target of ERK and p38MAPK by blockade of protein expression, transcriptional activity, and DNA binding. We have identified a novel GnRH-activated proline-rich tyrosine kinase 2-dependent ERK-mediated signal transduction pathway that specifically regulates Egr-1 activation of the LH beta-subunit proximal gene promoter, and thus provide insight into the molecular mechanisms required for differential regulation of gonadotropin gene expression.
Maudsley
Stuart
S
Medical Research Council Human Reproductive Sciences Unit, The Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh EH16 4TJ, Scotland, United Kingdom.
Naor
Zvi
Z
Bonfil
David
D
Davidson
Lindsay
L
Karali
Dimitra
D
Pawson
Adam J
AJ
Larder
Rachel
R
Pope
Caroline
C
Nelson
Nancy
N
Millar
Robert P
RP
Brown
Pamela
P
D000818:Animals; D051766:Early Growth Response Protein 1 / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005784:Gene Amplification; D005786:Gene Expression Regulation; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology*; D006801:Humans; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics*; D051379:Mice; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D012756:Sheep; D015398:Signal Transduction; D014158:Transcription, Genetic; D014162:Transfection
D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D037101:Luteinizing Hormone, beta Subunit; D007987:Gonadotropin-Releasing Hormone; D011505:Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases