Activation of mitogen-activated protein kinase phosphatase 2 by gonadotropin-releasing hormone.
The aim of these studies was to identify the signaling mechanism(s) that contribute to GnRH-induced expression of MAPK phosphatase (MKP)-2, a dual specificity phosphatase that selectively inactivates MAPKs. GnRH receptor activation induced MKP-2 expression in both clonal (alphaT3-1) and primary gonadotropes. Activation of PKC isozymes was sufficient and required for MKP-2 induction. Inhibition of the extracellular signal-regulated kinase ( ERK) or c-Jun N-terminal kinase (JNK) but not the p38 MAPK cascade was sufficient to block GnRH- induced MKP-2 expression. Induction of MKP-2 by GnRH was dependent on elevation in intracellular Ca(2+). Inhibition of Ca(2+) influx through L-type voltage-gated calcium channels blocked GnRH-induced MKP-2 expression. Depletion of intracellular Ca(2+) stores with thapsigargin blocked MKP-2 activation by GnRH independent of ERK and JNK activity. These results support the conclusion that MKP-2 induction by GnRH occurs via MAPK-dependent and -independent pathways. One mechanism requires GnRH-induced ERK and JNK activation, while a second MAPK-independent pathway requires a thapsigargin-sensitive calcium signal.[1]References
- Activation of mitogen-activated protein kinase phosphatase 2 by gonadotropin-releasing hormone. Zhang, T., Mulvaney, J.M., Roberson, M.S. Mol. Cell. Endocrinol. (2001) [Pubmed]
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