DHEAS-Specific Signalling in Cells of the Reproductive System
Final Report Abstract
We found that in the spermatogenic cell line GC-2, in the Sertoli cell line TM4 and in the brain-derived endothelial cell line b.End3 dehydroepiandrosterone sulfate (DHEAS) acts as an autonomous steroid hormone. In spermatogenic GC-2 cells DHEAS triggers the activation of a signaling cascade that includes the elements c-Src and Erk1/2 and results in the activation of the transcription factors CREB and ATF-1. DHEAS does not need to be converted to DHEA or a different steroid. This conclusion is based on the fact that steroid sulfatase is not detectable in the GC-2 cells and is further supported by the fact that the steroid sulfatase-specific inhibitor STX64 does affect the DHEAS-induced signaling cascade. The identified DHEAS-induced signaling resembles to a great extent the non-classical pathway of testosterone action. Nevertheless, silencing the expression of the androgen receptor (AR) by means of siRNA does not affect any of the DHEAS effects. In contrast, silencing the expression of the G-protein Gnα11 completely abolishes the entire DHEAS-induced signaling cascade. One can therefore assume that DHEAS exerts its actions through its interaction with a membrane-bound G protein-coupled receptor (GPCR) interacting with Gnα11. Can, however, DHEAS actions be of physiological relevance? This question was addressed by investigating DHEAS effects on the Sertoli cell line TM4 and on the brain-derived endothelial cell line bEnd.3. Both cell types are involved in the formation of crucial blood-tissue barriers: Sertoli cells in the formation of the blood-testis barrier (BTB) and brain endothelial cells in the formation of the blood-brain barrier (BBB). The BTB, formed by adjacent Sertoli cells, provides an immunologically privileged environment that protects the haploid stages of germ cells from cells of the immune system. The BBB, formed in the capillaries of the central nervous system by endothelial cells, regulates the exchange of factors and prevents passage of toxic substances from the bloodstream to the cerebrospinal fluid, thus ensuring an optimal environment for neuronal function. Both the BTB and the BBB are defined by the formation of tight junctions (TJs) between Sertoli and endothelial cells, respectively. In TM4 Sertoli cells, DHEAS at physiological concentrations of 1 µM induces activation of Erk1/2 and of transcription factors CREB and ATF-1. It also stimulates the expression of TJ proteins claudin-3 and claudin-5. In b.End3 cells, DHEAS stimulates the expression of zonula occludens-1 (ZO-1) and claudin-3. As a result, transepithelial and transendothelial electrical resistance increased, consistent with the formation of TJs between adjacent TM4 or b.End3 cells. All of the observed DHEAS effects are mediated through a GPCR interacting with Gnα11. This data demonstrate for the first time direct, hormone-like effects of DHEAS on spermatogenic and on blood-tissue barrier-forming cells. These effects might be of physiological relevance. The activation of the non-classical signaling pathway of steroid hormones in spermatogenic cells is known to be essential for sperm maturation. Formation of the BTB between Sertoli cells is crucial for the safeguarding of male fertility. Finally, assembly and maintenance of the BBB between brain endothelial cells is a prerequisite for normal cognitive function and its disturbance has been associated with a variety of neurological disorders.
Publications
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(2013) Dehydroepiandrosterone sulfate mediates activation of transcription factors CREB and ATF-1 via a Gα11-coupled receptor in the spermatogenic cell line GC-2. BBA - Mol Cell Res 1833:3064-3075
Shihan M, Kirch U, Scheiner-Bobis G
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(2014) Non-classical testosterone signaling is mediated by a G-protein-coupled receptor interacting with Gn#11. BBA - Mol Cell Res 1843:1172-1181
Shihan M, Bulldan A, Scheiner-Bobis G
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(2016) Dehydroepiandrosterone sulfate stimulates expression of blood-testis-barrier proteins claudin-3 and -5 and tight junction formation via a Gnα11-coupled receptor in Sertoli cells. PLOS one 11(3):e0150143
Papadopoulos D, Dietze R, Shihan M, Kirch U and Scheiner-Bobis G
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(2017) Dehydroepiandrosterone sulfate augments blood-brain barrier and tight junction protein expression in brain endothelial cells. BBA - Mol Cell Res 1864:1382-1392
Papadopoulos D, Scheiner-Bobis G
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(2017) Physiological implications of DHEAS- induced non-classical steroid hormone signaling. J Steroid Biochem Mol Biol
Papadopoulos D, Shihan M, and Scheiner-Bobis G
