Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2009 Apr 28;106(17):7221-6.
doi: 10.1073/pnas.0812597106. Epub 2009 Apr 9.

p21-Activated kinase mediates rapid estradiol-negative feedback actions in the reproductive axis

Zhen Zhao  1 , Cheryl Park, Melissa A McDevitt, Christine Glidewell-Kenney, Pierre Chambon, Jeffrey Weiss, J Larry Jameson, Jon E Levine
Affiliations

p21-Activated kinase mediates rapid estradiol-negative feedback actions in the reproductive axis

Zhen Zhao et al. Proc Natl Acad Sci U S A. .

Abstract

Nonclassical estrogen receptor alpha (ERalpha) signaling can mediate E(2) negative feedback actions in the reproductive axis; however, downstream pathways conveying these effects remain unclear. These studies tested the hypothesis that p21-activated kinase 1 (PAK1), a serine/threonine kinase rapidly activated by E(2) in nonneural cells, functions as a downstream node for E(2) signaling pathways in cells of the preoptic area, and it may thereby mediate E(2) negative feedback effects. Treatment of ovariectomized (OVX) rats with estradiol benzoate (EB) caused rapid and transient induction of phosphorylated PAK1 immunoreactivity in the medial preoptic nucleus (MPN) but not the arcuate nucleus. To determine whether rapid induction of PAK phosphorylation by E(2) is mediated by nonclassical [estrogen response element (ERE)-independent] ERalpha signaling, we used female ERalpha null (ERalpha(-/-)) mice possessing an ER knock-in mutation (E207A/G208A; AA), in which the mutant ERalpha is incapable of binding DNA and can signal only through membrane-initiated or ERE-independent genotropic pathways (ERalpha(-/AA) mice). After 1-h EB treatment, the number of pPAK1-immunoreactive cells in the MPN was increased in both wild-type (ERalpha(+/+)) and ERalpha(-/AA) mice but was unchanged in ERalpha(-/-) mice. Serum luteinizing hormone (LH) was likewise suppressed within 1 h after EB treatment in ERalpha(+/+) and ERalpha(-/AA) but not ERalpha(-/ -) mice. In OVX rats, 5-min intracerebroventricular infusion of a PAK inhibitor peptide but not control peptide blocked rapid EB suppression of LH secretion. Taken together, our findings implicate PAK1 activation subsequent to nonclassical ERalpha signaling as an important component of the negative feedback actions of E(2) in the brain.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Time dependence of E2-induced pPAK1-Ir in the MPN of female rats. OVX females rats treated with oil or EB were killed at 0.5, 1, 2, and 4 h after injection. (A) Representative photomicrographs of pPAK1-Ir in the MPN and adjacent regions of OVX rats 0.5 h after oil or EB injection. (Scale bar: 100 μm.) The number of pPAK1-Ir cells in the MPNl (B) and MPNm (C) was significantly greater after 0.5 and 1 h of EB treatment compared with corresponding oil treatment (n = 6–9). Data are represented as the mean ± SEM (***, P < 0.001; **, P < 0.01; *, P < 0.05).
Fig. 2.
Fig. 2.
E2-independent pPAK1-Ir in the AN of female rats. Animals were treated as described in Fig. 1. (A) Representative photomicrographs of pPAK1-Ir in the AN and adjacent regions of OVX rats 1 h after oil or EB injection. (Scale bar: 100 μm.) The number of pPAK1-Ir neurons in the AN was not significantly different after EB treatment compared with corresponding oil treatment (B). Data are represented as the mean ± SEM (n = 6–9).
Fig. 3.
Fig. 3.
E2-induced pPAK1-Ir in the MPN of female ERα+/+, ERα−/−, and ERα−/AA mice. OVX female mice treated with oil or EB were killed at 1 h after injection. (A) Representative photomicrographs of pPAK1-Ir in the MPN and adjacent regions of OVX mice 1 h after oil or EB injection. (Scale bar: 100 μm.) The number of pPAK1-Ir cells was significantly increased in the MPNl (B) and MPNm (C) in ERα+/+ and ERα−/AA but not ERα−/− mice (n = 5–9). Data are represented as the mean ± SEM (**, P < 0.01; *, P < 0.05).
Fig. 4.
Fig. 4.
E2-independent pPAK1-Ir in the AN of female ERα+/+, ERα−/−, and ERα−/AA mice. Animals were treated as described in Fig. 3. (A) Representative photomicrographs of pPAK1-Ir in the AN and adjacent regions of OVX mice 1 h after oil or EB injection. (Scale bar: 100 μm.) The number of pPAK1-Ir cells in the AN was not significantly different after EB treatment compared with values in animals receiving corresponding oil treatment (B). Data are represented as the mean ± SEM (n = 5–8).
Fig. 5.
Fig. 5.
The ERE-independent ERα signaling pathway is sufficient to convey rapid E2 negative feedback actions. Serum LH from intact, OVX, and OVX/EB-injected (1 h) females in the morning (n = 8–14). Data are represented as the mean ± SEM (***, P < 0.001; *, P < 0.05).
Fig. 6.
Fig. 6.
Inhibition of PAK phosphorylation. Inhibition of PAK phosphorylation by treatment with PAK18 inhibitory peptide to GT1-7 cells (A) and in the lateral ventricle of OVX rats (B) for 1 h (n = 4–6). (Scale bar: 100 μm.) Data are represented as the mean ± SEM (**, P < 0.01; *, P < 0.05).
Fig. 7.
Fig. 7.
Inhibition of PAK phosphorylation blocks acute E2 suppression of LH secretions. The LH level was significantly decreased at 1 h after R192A icv infusion and EB s.c. injection. In the contrast, the LH level was not significantly altered by treatment with PAK18 and EB (n = 4–6). Data are represented as the mean ± SEM (***, P < 0.001; *, P < 0.05).
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Leipheimer RE, Bona-Gallo A, Gallo RV. Influence of estradiol and progesterone on pulsatile LH secretion in 8-day ovariectomized rats. Neuroendocrinology. 1986;43:300–307. - PubMed
    1. Johnston CA, Tesone M, Negro-Vilar A. Cellular mechanisms of acute estrogen negative feedback on LH secretion: Norepinephrine, dopamine and 5-hydroxytryptamine metabolism in discrete regions of the rat brain. Brain Res Bull. 1984;13:363–369. - PubMed
    1. Couse JF, Yates MM, Walker VR, Korach KS. Characterization of the hypothalamic-pituitary-gonadal axis in estrogen receptor (ER) Null mice reveals hypergonadism and endocrine sex reversal in females lacking ERalpha but not ERbeta. Mol Endocrinol. 2003;17:1039–1053. - PubMed
    1. Wintermantel TM, et al. Definition of estrogen receptor pathway critical for estrogen positive feedback to gonadotropin-releasing hormone neurons and fertility. Neuron. 2006;52:271–280. - PMC - PubMed
    1. Coleman KM, Smith CL. Intracellular signaling pathways: Nongenomic actions of estrogens and ligand-independent activation of estrogen receptors. Front Biosci. 2001;6:D1379–D1391. - PubMed

Publication types