Nadine Martinat

The ERK-dependent signalling is stage-specifically modulated by FSH, during primary Sertoli cell maturation

Primary cultures of Sertoli cells provide an interesting model to study how signalling pathways induced by a single hormone in a single cell type evolve, depending on the developmental stage. In vivo, follicle-stimulating hormone (FSH) induces proliferation of Sertoli cells in neonate and controls the subsequent differentiation of the entire population. Molecular mechanisms underlying Sertoli cell pleiotropic responses to FSH have long been investigated. But to date, only cAMP-dependent kinase (PKA) activation has been reported to account for most FSH biological activities in male. Here, we demonstrate that FSH activates the ERK MAP kinase pathway following dual coupling of the FSH-R both to Gs and to Gi heterotrimeric proteins, in a PKA- and also Src-dependent manner. This activation is required for FSH-induced proliferation of Sertoli cells isolated 5 days after birth. Consistently, we show that the ERK-mediated FSH mitogenic effect triggers upregulation of cyclin D1. In sharp contrast, at 19 days after birth, as cells proceed through their differentiation program, the ERK pathway is dramatically inhibited by FSH treatment. Taken together, these results show that FSH can exert opposite effects on the ERK signalling cascade during the maturation process of Sertoli cells. Thus, signalling modules triggered by the FSH-R evolve dynamically throughout development of FSH natural target cells.

G Protein-Coupled Receptor Kinases and Beta Arrestins Are Relocalized and Attenuate Cyclic 3′,5′-Adenosine Monophosphate Response to Follicle-Stimulating Hormone in Rat Primary Sertoli Cells

Abstract The FSH receptor (FSH-R) is a member of the rhodopsin-like subfamily of G protein-coupled receptors that undergoes homologous desensitization upon agonist stimulation. In immortalized cell lines overexpressing the FSH-R, G protein-coupled receptor kinases (GRKs) and β-arrestins are involved in the phosphorylation, uncoupling, and internalization of this receptor. In an effort to appreciate the physiological relevance of GRK/β-arrestin actions in natural FSH-R-bearing cells, we used primary rat Sertoli cells as a model. GRK2, -3, -5, -6a, and -6b and β-arrestins 1 and 2 were expressed in primary rat Sertoli cells. Overexpression of these different GRKs and β-arrestins in primary rat Sertoli cells significantly attenuated the FSH-induced cAMP response, and FSH rapidly triggered a relocalization of endogenously expressed GRK2, -3, -5, and -6 and β-arrestins 1 and 2 from the cytosol to the membranes. These results highlight the relationship existing between the GRK/β-arrestin regulatory system and the FSH-R signaling machinery in a physiological model.

Rapid in vitro desensitization of the testosterone response in rat Ley dig cells by sub-active concentrations of porcine luteinizing hormone

We have studied in rat Leydig cells, the effect of sub‐active concentrations of porcine LH on the subsequent stimulation of the cAMP and testosterone production by a sub‐maximal concentration of pLH or hCG. We found that extremely low concentrations of pLH (0.01–2.0 ) were able to induce rapidly a partial but highly significative desensitization of the testosterone response without affecting the cyclic AMP response. These data indicate that desensitization of the steroidogenic response might be due to some lesion beyond cAMP formation or at the level of one discrete compartment of cyclic AMP, directly involved in the control of steroidogenesis. Moreover, our data strongly suggest that the basal circulating concentrations of LH can exert an inhibitory control on the testosterone response to LH pulses in vivo.

Immunocytochemical localization of LH, FSH and TSH in the fetal porcine pituitary

SummaryAntibodies (i) against porcine LH (A-pLH) and porcine FSH (A-pFSH), and (ii) against their subunits porcine LHβ, porcine FSHβ, porcine TSHβ, and rat LHα were used in the present study. The aim of this study was (1) to detect by the use of the immunoperoxidase technique the earliest stages of immunoreactive gonadotropic and thyrotropic cells, and (2) to study the development of the synthesis and the storage of LH, FSH and TSH in the fetal porcine anterior pituitary. The following results were obtained: (1) LH, FSH and TSH appeared between days 40 and 45 of fetal life; immunoreactive LH was found on day 40, immunoreactive TSH and FSH at day 45; thus, the first gonadotropic cells containing both LH and FSH were observed at day 45 (LH/FSH cells). (2) The α-subunit appeared to be present earlier than the β-subunits or complete gonadotropic and thyrotropic hormones. (3) LH became manifest earlier than FSH.These findings showed clearly the onset of the synthesis of LH and FSH at days 40 to 45 of fetal life, and a progress until day 75, being complete at day 80 and resulting in a population of LH/FSH cells. At about day 90, the most predominant type of gonadotropic cell was the LH/FSH cell; however, some cells appeared to be exclusively LH cells.

Histoimmunological identification of a prolactin-like substance in rodent testis

SummaryAnti-rat prolactin (PRL) antibodies were localized by histoimmunological methods in the cytoplasm of testicular interstitial cells, Sertoli cells, spermatogonia and primary spermatocytes of the rat and mouse. Control of specificity by affinity chromatography methods showed this PRL-like material to be non-specific in these testicular tissues, but specific in adenohypophyseal cells. These results are discussed.