Signal Transduction Mediating Gene Expression of SP1, LHβ-Subunit and GH in Response to GnRH or GHRH in the Postnatal and Fetal Porcine Anterior Pituitary in Vitro

Abstract

To clarify signal transduction pathways mediating putative gene expression of transcription factor SP1 (selective promoter factor 1 or specificity protein 1) by GnRH or GHRH porcine anterior pituitary monolayer cultures were exposed for various time periods to GnRH, GHRH, activators of adenylate cyclase (AC) or proteinkinase C (PKC), and mRNA levels of SP1, LHbeta-subunit, and GH were determined by multiplex RT-PCR. In many experiments LH and GH release were measured as well for comparison. Another approach was to inactivate AC, PKC, or proteinkinase A (PKA) by specific inhibitors, MDL, GFX, and H89, respectively. Postnatally (4 weeks) SP1 mRNA level was maximally increased by GnRH, GHRH and both by activation of AC or PKC after 2 h of exposure. Two-hour stimulation of SP1 mRNA levels by dbcAMP was totally blocked by H89, while this inhibitor not clearly blocked GHRH stimulated SP1 mRNA levels. Stimulation of LHbeta mRNA by GnRH was suppressed by inactivation of AC or of PKC but not by inactivation of PKA. Inactivation of AC or PKA but not of PKC inhibited GHRH induced GH mRNA. Already at day 50 of fetal life (and likewise day 80) SP1 mRNA levels were stimulated by GHRH or activation of AC, but not by GnRH or activation of PKC. The results are consistent with the notion that SP1 plays an important role 1) in conferring GnRH responsiveness to the LHbeta-subunit gene by mediating the actions of both AC and PKC and 2) in conferring GHRH responsiveness to the GH gene through activation of the AC probably PKA pathway. Furthermore, the data are in line with the view that the GHRH/AC/SP1/GH pathway develops earlier during fetal life than the GnRH/PKC/SP1/LHbeta pathway.

Molecular cloning and functional analysis of the zebrafish luteinizing hormone beta subunit (LH<beta>) promoter

“…All photographs were taken with a 1009 lens on an Olympus IX70 microscope LH\beta[ gene transcription increased with acute activation (6 h) of the GnRH receptor or PKC, but not calcium influx, in a promoter activity assay. Blocking PKC induction prevented the acute action of the GnRH and unmasked the acute repression of LH\beta[ transcription by calcium (Vasilyev et al 2002;Zeng et al 2005). Of interest is the fact that others and ourselves have observed significantly different activities of the LH\beta[ promoter after treatment with various calcium-affecting drugs, and our results showed that EGTA inhibits zebrafish LH\beta[ promoter activity, but others found that it did not affect the promoter (Call and Wolfe 1999).…”

Novel Regulatory Factors in the Hypothalamic-Pituitary-Ovarian Axis of Hens at Four Developmental Stages

“…Furthermore, TATA binding protein ( TBP ), general transcription factor IIH subunit 2 ( GTF2H2 ), and general transcription factor IIB ( GTF2B ) as general transcription factors, assemble on the promoters of the gene transcribed by RNA polymerase II, which trigger transcriptional regulation by interacting with gene regulatory factors ( Sperling, 2007 ; Bieniossek et al, 2013 ). In general, TBP interacts with TBP-associated factors ( TAFs ) to identify and activate gene transcription, of which selective promoter factor 1 ( SP-1 ), as one of the TAFs, could induce GnRH responsiveness to the LHβ promoter by mediating the actions of both adenylate cyclase (AC) and protein kinase C (PKC) ( Zeng et al, 2005 ). Moreover, TAF9 and GTF2H2 have been shown to play roles in the estrogen signaling pathway ( Markaverich et al, 2011 ).…”

Localization of Fertility Factor SP22 to Specific Cell Types Within the Anterior Pituitary Gland

“…For example, the human SP22 promoter was activated by Sp1 (34). In tum, Spl has been implicated in the GnRH-induced stimulation of the LHp gene promoter (35,36). SP22 has been linked to nuclear AR function.…”