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

doi:10.1073/pnas.0812597106

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

^aDepartment of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208-3113;
^bDepartment of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611; and
^cInstitut de Génétique et de Biologie Moléculaire et Cellulaire, 1 Rue Laurent Fries, 67404 Illkirch, France

Edited by Donald W. Pfaff, The Rockefeller University, New York, NY, and approved March 2, 2009 (received for review December 11, 2008)

Abstract

Nonclassical estrogen receptor α (ERα) signaling can mediate E₂ 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 E₂ in nonneural cells, functions as a downstream node for E₂ signaling pathways in cells of the preoptic area, and it may thereby mediate E₂ 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 E₂ is mediated by nonclassical [estrogen response element (ERE)-independent] ERα signaling, we used female ERα null (ERα^−/−) mice possessing an ER knock-in mutation (E207A/G208A; AA), in which the mutant ERα is incapable of binding DNA and can signal only through membrane-initiated or ERE-independent genotropic pathways (ERα^−/AA mice). After 1-h EB treatment, the number of pPAK1-immunoreactive cells in the MPN was increased in both wild-type (ERα^+/+) and ERα^−/AA mice but was unchanged in ERα^−/− mice. Serum luteinizing hormone (LH) was likewise suppressed within 1 h after EB treatment in ERα^+/+ and ERα^−/AA but not ERα^{−/ −} 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 ERα signaling as an important component of the negative feedback actions of E₂ in the brain.

Footnotes

¹To whom correspondence should be addressed. E-mail: jlevine{at}northwestern.edu
Author contributions: Z.Z., C.P., M.A.M., J.L.J., and J.E.L. designed research; Z.Z., C.P., and M.A.M. performed research; C.G.-K., P.C., and J.W. contributed new reagents/analytic tools; Z.Z., J.L.J., and J.E.L. analyzed data; and Z.Z., J.L.J., and J.E.L. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
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