The Role of ZIP9 and Androgen Receptor in the Establishment of Tight Junctions between Adult Rat Sertoli Cells.

The blood-testis barrier (BTB) is formed from tight junctions (TJs) between Sertoli cells. This dynamic structure, which establishes an immune-privileged environment protecting haploid germ cells formed in puberty from cells of the innate immune system, protects male fertility. Testosterone produced in Leydig cells is one of the main regulators of TJ protein expression and BTB dynamics.

Tetrapeptides Modelled to the Androgen Binding Site of ZIP9 Stimulate Expression of Tight Junction Proteins and Tight Junction Formation in Sertoli Cells.

Androgens stimulate the expression of tight junction (TJ) proteins and the formation of the blood-testis barrier (BTB). Interactions of testosterone with the zinc transporter ZIP9 stimulate the expression of TJ-forming proteins and promote TJ formation in Sertoli cells. In order to investigate androgenic effects mediated by ZIP9 but not by the nuclear androgen receptor (AR), the effects of three tetrapeptides fitting the androgen binding site of ZIP9 were compared with those induced by testosterone in a Sertoli cell line expressing ZIP9 but not the AR.

The Effects of Tetrapeptides Designed to Fit the Androgen Binding Site of ZIP9 on Myogenic and Osteogenic Cells.

ZIP9 is a recently identified membrane-bound androgen receptor of physiological significance that may mediate certain physiological responses to androgens. Using in silico methods, six tetrapeptides with the best docking properties at the testosterone binding site of ZIP9 were synthesized and further investigated. All tetrapeptides displaced T-BSA-FITC, a membrane-impermeable testosterone analog, from the surface of mouse myogenic L6 cells that express ZIP9 but not the classical androgen receptor (AR).

DHEAS prevents pro-metastatic and proliferative effects of 17ß-estradiol on MCF-7 breast cancer cells.

It is generally assumed that circulating dehydroepiandrosterone sulfate (DHEAS) can be desulfated and further metabolized to estrogen, which is of concern for all patients with estrogen-responsive breast cancer. We addressed this issue by comparing the effects of DHEAS, its desulfated form DHEA, and 17ß-estradiol on human metastatic, estrogen-responsive MCF-7 breast cancer cells. Physiological concentrations of DHEAS promoted phosphorylation of Erk1/2, whereas DHEA and 17ß-estradiol failed to stimulate Erk1/2 phosphorylation, indicating that the sulfated steroid acts as an autonomous hormone.

Cardiotonic steroid ouabain stimulates steroidogenesis in Leydig cells via the α3 isoform of the sodium pump.

Cardiotonic steroids such as ouabain are potent inhibitors of the sodium pump and have been widely used for centuries in the treatment of congestive heart failure. In recent decades, however, they have also been identified as hormone-like molecules that trigger signaling cascades of physiological relevance by using the various sodium pump α subunit isoforms as receptors. The murine Leydig cell line MLTC-1 expresses both the ubiquitous, relatively ouabain-insensitive α1 isoform of the sodium pump and the ouabain-sensitive α3 isoform that is normally found in neuronal cells.

ZIP9 but not the androgen receptor mediates testosterone-induced migratory activity of metastatic prostate cancer cells.

LNCaP cells are derived from a metastatic lesion of human prostate adenocarcinoma. They express the classical androgen receptor (AR) and ZIP9, a Zn transporter that also binds testosterone and mediates signaling by interacting with G-proteins. Our results show that LNCaP cells respond to testosterone by mobilizing their migratory machinery.

Impairment of the Gnα11-controlled expression of claudin-1 and MMP-9 and collective migration of human breast cancer MCF-7 cells by DHEAS.

Although dehydroepiandrosterone sulfate (DHEAS) constitutes the most abundant steroid in humans, in-depth investigations of its effects are rather scarce. We address here DHEAS effects on the estrogen receptor-positive metastatic human breast cancer cell line MCF-7. We focus on DHEAS-mediated signaling that might influence expression of claudin-1 and matrix metalloproteinase-9 (MMP-9), both known to be critical factors for migration and invasiveness of various cancers, including breast cancer cells.

Testosterone/bicalutamide antagonism at the predicted extracellular androgen binding site of ZIP9.

ZIP9 is a Zn transporter, testosterone receptor, and mediator of signaling events through G-proteins. Despite these pivotal properties, however, its physiological and pathophysiological significance has not yet been comprehensively addressed. Using a cell line that lacks the classical androgen receptor we show that ZIP9-mediated phosphorylation of Erk1/2, CREB, or ATF-1 and expression of claudin-5 and zonula occludens-1 by testosterone can be completely antagonized by bicalutamide (Casodex), an anti-androgen of significant clinical impact.

Signaling events associated with gonadotropin releasing hormone-agonist-induced hormonal castration and its reversal in canines.

A gonadotropin-releasing hormone agonist (GnRH-A) implant induces hormonal castration in dogs that is associated with reduced prostate and testes size. We address the molecular events associated with hormonal castration by examining GnRH-A effects on expression and phosphorylation of a number of key signaling proteins. Male beagles were treated for 5 months with a GnRH-A implant, and then surgically castrated at 0, 3, 6, 12, and, 24 weeks after implant removal; untreated animals served as controls.

Non-classical testosterone signaling mediated through ZIP9 stimulates claudin expression and tight junction formation in Sertoli cells.

In the classical signaling pathway, testosterone regulates gene expression by activating the cytosolic/nuclear androgen receptor. In the non-classical pathway, testosterone activates cytosolic signaling cascades that are normally triggered by growth factors. The nature of the receptor involved in this signaling pathway is a source of controversy.

Non-classical testosterone signaling is mediated by a G-protein-coupled receptor interacting with Gnα11.

Testosterone is known to mediate its effects by two different mechanisms of action. In the so-called "classical" pathway testosterone binds to cytosolic androgen receptors (AR), which essentially function as ligand-activated transcription factors. Once activated, these receptors bind to DNA and activate the expression of target genes.