Ecdysteroids affect female reproductive status and outcome of contest over hosts in the parasitoid wasp Eupelmus vuilleti.

Ecdysteroids are a family of insect hormones that may play a role in modulating aggressive behavior in reproductive contexts. In Hymenoptera, the few studies investigating the link between ecdysteroid titers, reproduction and aggressiveness during contests concern solely eusocial species. Here, we explored whether ecdysteroid titers influenced female reproductive status as well as aggressiveness and resolution of conflict in a solitary ectoparasitoid, Eupelmus vuilleti (Hymenoptera: Eupelmidae). Eupelmus vuilleti females parasitize and feed upon juvenile stages of Callosobruchus maculatus (Coleoptera: Bruchidae). When two E. vuilleti females are simultaneously present on a patch, they tend to protect the host they exploit by displaying aggressive behaviors towards conspecific competitors. To our knowledge, nothing is known about the association between ecdysteroids and aggressiveness or the outcome of contests for host access in solitary insects. First, we quantified ecdysteroid titers that naturally circulate in females without fighting experience and after a contest over host access. Ecdysteroid titers measured after the contest did not correlate with female aggressiveness during the contest, but winner wasps had higher titers than both losers and females that did not fight. Then, we manipulated hormone titers via injection: ecdysone favored egg maturation (i.e., gonadotropic effect) within 24 h and increased almost immediately the females' probability of winning host access without affecting their aggressiveness. Our results represent an important step in understanding how hormones, such as ecdysteroids, mediate insect behavior during intraspecific competition.

An evolutionary approach to recover genes predominantly expressed in the testes of the zebrafish, chicken and mouse.

BACKGROUND: Previously, we have demonstrated that genes involved in ovarian function are highly conserved throughout evolution. In this study, we aimed to document the conservation of genes involved in spermatogenesis from flies to vertebrates and their expression profiles in vertebrates. RESULTS: We retrieved 379 Drosophila melanogaster genes that are functionally involved in male reproduction according to their mutant phenotypes and listed their vertebrate orthologs. 83% of the fly genes have at least one vertebrate ortholog for a total of 625 mouse orthologs. This conservation percentage is almost twice as high as the 42% rate for the whole fly genome and is similar to that previously found for genes preferentially expressed in ovaries. Of the 625 mouse orthologs, we selected 68 mouse genes of interest, 42 of which exhibited a predominant relative expression in testes and 26 were their paralogs. These 68 mouse genes exhibited 144 and 60 orthologs in chicken and zebrafish, respectively, gathered in 28 groups of paralogs. Almost two thirds of the chicken orthologs and half of the zebrafish orthologs exhibited a relative expression ≥50% in testis. Finally, our focus on functional in silico data demonstrated that most of these genes were involved in the germ cell process, primarily in structure elaboration/maintenance and in acid nucleic metabolism. CONCLUSION: Our work confirms that the genes involved in germ cell development are highly conserved across evolution in vertebrates and invertebrates and display a high rate of conservation of preferential testicular expression among vertebrates. Among the genes highlighted in this study, three mouse genes (Lrrc46, Pabpc6 and Pkd2l1) have not previously been described in the testes, neither their zebrafish nor chicken orthologs. The phylogenetic approach developed in this study finally allows considering new testicular genes for further fundamental studies in vertebrates, including model species (mouse and zebrafish).

GPCR activation of Ras and PI3Kc in neutrophils depends on PLCb2/b3 and the RasGEF RasGRP4.

The molecular mechanisms by which receptors regulate the Ras Binding Domains of the PIP3-generating, class I PI3Ks remain poorly understood, despite their importance in a range of biological settings, including tumorigenesis, activation of neutrophils by pro-inflammatory mediators, chemotaxis of Dictyostelium and cell growth in Drosophila. We provide evidence that G protein-coupled receptors (GPCRs) can stimulate PLCb2/b3 and diacylglycerol- dependent activation of the RasGEF, RasGRP4 in neutrophils. The genetic loss of RasGRP4 phenocopies knock-in of a Ras-insensitive version of PI3Kc in its effects on PI3Kc-dependent PIP3 accumulation, PKB activation, chemokinesis and reactive oxygen species (ROS) formation. These results establish a new mechanism by which GPCRs can stimulate Ras, and the broadly important principle that PLCs can control activation of class I PI3Ks.

Limited effects of a glyphosate-based herbicide on the behaviour and immunity of males from six populations of the European earwig.

The use of herbicides on crops often results in unintentional, low-dose exposure of non-target organisms, such as insects. While these exposures are increasingly known to alter the survival and physiology of insects, it remains unclear whether these effects can vary between populations and modify other fitness-related traits, such as behaviour and immunity. Here, we addressed these questions by testing the effects of sublethal exposure to a glyphosate-based herbicide (GBH) on the behaviour and immunity of European earwig males from six natural populations. We exposed each male to a dose of a common GBH (Roundup©) that was either recommended for crops, five times lower than that recommended for crops, or to a control solution. Twenty-four hours later, we measured the activity, boldness, and aggregation of each male. We then exposed them to an entomopathogenic fungus, monitored their survival for 6 weeks, and measured the immune response of the survivors. We found a condition-dependent effect of GBH exposure on male activity. Exposure to low doses induced a positive association between activity and weight, which was not observed in the high-dose and control groups. However, GBH had no effect on any of the other measured traits. All these results were consistent across the six populations tested, although we did find population-specific differences in almost all measurements on males. Further research is now needed to better understand the dose-response to GBH on male activity and its biological impact, as well as to evaluate the effectiveness of detoxification processes in this species. Overall, these results emphasise the importance of investigating the effects of herbicides on insects to expand our general understanding of the use and potential risks of plant protection products in integrated pest management programs.

Unveiling Molecular Effects of the Secondary Metabolite 2-Dodecanone in the Model Hymenopteran Nasonia vitripennis.

Over the past decade, multiple studies have suggested that the secondary metabolites produced by plants against herbivorous insects could be used as biopesticides. However, as the molecular mechanism of action of these compounds remains unknown, it is difficult to predict how they would affect non-target insects; thus, their innocuity needs to be clarified. Here, we investigate, from the molecular level to the organism, the responses of a useful parasitic insect Nasonia vitripennis (Walker, 1836) being exposed at the pupae stage for 48 h (up to 6 days) to sublethal doses (5 µg/L and 500 µg/L) of 2-Dodecanone. 2-Dodecanone altered the gene expression of genes related to ecdysone-related pathways, biotransformation, and cell homeostasis. A significant induction of ecdysone response-genes (EcR, usp, E78, Hr4, Hr38) was detected, despite no significant differences in ecdysteroid levels. Regarding the cell homeostasis processes, the gene l(2)efl was differentially altered in both experimental conditions, and a dose-dependent induction of hex81 was observed. 2-Dodecanone also triggered an induction of Cyp6aQ5 activity. Finally, 2-Dodecanone exposure had a significant effect on neither development time, energy reserves, nor egg-laying capacity; no potential genotoxicity was detected. For the first time, this study shows evidence that 2-Dodecanone can modulate gene expression and interfere with the ecdysone signalling pathway in N. vitripennis. This could lead to potential endocrine alterations and highlight the suitability of this organism to improve our general understanding of the molecular effects of plant defences in insects. Our findings provide new insights into the toxicity of 2-Dodecanone that could potentially be explored in other species and under field conditions for plant protection and pest management as a means to reduce reliance on synthetic pesticides.

[Parasitic wasps, a model for studying male subfertility]. / Les hyménoptères parasitoïdes: des modèles pour l'étude de l'hypofertilité mâle.

Many studies have reported an increase in male reproductive disorders due to the environment. Despite their ecological importance invertebrates have been poorly studied; they are yet affected in the same way as vertebrates by changes in the environment. Different stresses made on parasitic wasps are able to induce a male subfertility. These insects are easy to rear in the laboratory, used to control insect pests, and have other benefits presented in this article. Parasitic wasps are good models for understanding the mechanisms inducing subfertility and may provide new areas for research in vertebrates.

Sublethal doses of pyriproxyfen stimulate reproduction and aggressive behavior in a non-target parasitoid wasp.

Insecticides are commonly used to control populations of pests and disease vectors. However, they can have multiple unintended effects on non-target species. Assessing their impacts on the physiology and behavior of beneficial insects, such as biological control agents, is thus necessary to gain insight into the diversity and nature of such side effects. Here, we investigated the effect of sublethal doses of the endocrine disrupting insecticide pyriproxyfen, a juvenile hormone agonist, on females of the solitary ectoparasitoid Eupelmus vuilleti (Hymenoptera: Eupelmidae). These parasitoid wasps can be used as biological control agents to control the cowpea weevil, Callosobruchus maculatus (Coleoptera: Bruchidae), that infests cowpea seeds, Vigna unguiculata (Fabacea). To do so, in addition to classical measures on female fecundity and survival, we focused on female behaviors that can have important consequences on female fitness and host exploitation. First, we showed that pyriproxyfen stimulated egg production without affecting female survival. Second, we observed that low doses of this insecticide had no effect on females' exploration and host discrimination ability but stimulated their aggressiveness when fighting for host access. Although a negative impact on other life-history traits cannot be ruled out at this point, these results showed low doses of pyriproxyfen can have unintended positive effects on ectoparasitoid E. vuilleti females, by enhancing at least temporarily their reproduction and host access in a situation of competition. Our work thus highlights the importance of studying the diversity of possible unintended sublethal effects of pesticides on beneficial insects.

Exposure to pyriproxyfen (juvenile hormone agonist) does not alter maternal care and reproduction in the European earwig.

Sublethal exposure to pesticides can alter the survival and reproduction of a wide range of non-target organisms. However, it remains unclear whether this exposure can alter behaviours that are often essential for long-term population dynamics and maintenance, such as parental care. In this study, we tested the effect of pyriproxyfen exposure (an insect growth regulator) on maternal care in the European earwig, an insect that is both used in pest control in pip-fruit orchards and considered a pest in stone fruit orchards. We exposed 424 females at doses either 10 times lower, equivalent or 10 times higher than normal application rates in French orchards. As maternal care can change over the weeks of family life, we exposed the earwig mothers at five different days before and after egg hatching. We then measured the expression of ten forms of maternal care towards eggs and juveniles, six non-caring behaviours, eggs and juvenile development, metabolic reserves in mothers at egg hatching and females' production of a terminal clutch. First, our results revealed that the three tested doses of pyriproxyfen were non-lethal and confirmed that maternal care decreased throughout both pre- and post-hatching family life. However, we did not detect any effect of pyriproxyfen on maternal care and non-care behaviours, eggs and juvenile development, quantities of lipids, proteins and glycogen in mothers at egg hatching, and on the production of a future clutch. Overall, these findings suggest that the maximal doses of pyriproxyfen authorized in French orchards is likely to have limited effects on the short- and long-term maintenance of populations of the European earwig and raises fundamental questions about the nature of the link between juvenile hormone and parental care in insects.

Sublethal exposure to deltamethrin stimulates reproduction and has limited effects on post-hatching maternal care in the European earwig.

Although pesticides are typically used to limit pest population, the diversity and nature of their unintentional effects on non-target organisms remain unclear. Better understanding these effects requires to carry out risk assessments on key physiological and behavioral processes specific to beneficial insects. In this study, we addressed this question by exposing mothers of the European earwig (a beneficial insect) to two sublethal doses of deltamethrin (a common pesticide in agriculture) during family life and measured the short- and long-term effects on a series of behavioral, physiological, and reproductive traits. Somewhat surprisingly, our results first revealed that high and low doses of deltamethrin enhanced mothers' future reproduction by augmenting their likelihood to produce a second clutch, shortening the number of days until its production, and increasing the resulting number of eggs and their hatching rate. Conversely, the high dose of deltamethrin was detrimental, as it limited maternal brood defence, and reduced food consumption and expression of self-grooming. Finally, other traits were independent of deltamethrin exposure, such as three proxies of family interactions (i.e., distance to the brood, occurrence, and duration of mother-offspring contacts), mothers' walking distance, and mother weight gain during family life. Our study overall demonstrates that sublethal exposure to a pesticide such as deltamethrin can have both positive and negative effects on non-target beneficial insects. It thus emphasizes that focusing on narrow parameters can lead to misleading conclusions about the unintended impacts of pesticides in treated agro-ecosystems and call for better considering this parameters diversity in integrated pest management programs.

A comparative genomic approach using mouse and fruit fly data to discover genes involved in testis function in hymenopterans with a focus on Nasonia vitripennis.

BACKGROUND: Spermatogenesis appears to be a relatively well-conserved process even among distantly related animal taxa such as invertebrates and vertebrates. Although Hymenopterans share many characteristics with other organisms, their complex haplodiploid reproduction system is still relatively unknown. However, they serve as a complementary insect model to Drosophila for studying functional male fertility. In this study, we used a comparative method combining taxonomic, phenotypic data and gene expression to identify candidate genes that could play a significant role in spermatogenesis in hymenopterans. RESULTS: Of the 546 mouse genes predominantly or exclusively expressed in the mouse testes, 36% had at least one ortholog in the fruit fly. Of these genes, 68% had at least one ortholog in one of the six hymenopteran species we examined. Based on their gene expression profiles in fruit fly testes, 71 of these genes were hypothesized to play a marked role in testis function. Forty-three of these 71 genes had an ortholog in at least one of the six hymenopteran species examined, and their enriched GO terms were related to the G2/M transition or to cilium organization, assembly, or movement. Second, of the 379 genes putatively involved in male fertility in Drosophila, 224 had at least one ortholog in each of the six Hymenoptera species. Finally, we showed that 199 of these genes were expressed in early pupal testis in Nasonia vitripennis; 86 exhibited a high level of expression, and 54 displayed modulated expression during meiosis. CONCLUSIONS: In this study combining phylogenetic and experimental approaches, we highlighted genes that may have a major role in gametogenesis in hymenopterans; an essential prerequisite for further research on functional importance of these genes.

Testis cord differentiation after the sex determination stage is independent of Sox9 but fails in the combined absence of Sox9 and Sox8.

Sox9 and Sox8 are transcription factors expressed in embryonic and postnatal Sertoli cells of the mouse testis. Sox9 inactivation prior to the sex determination stage leads to complete XY sex reversal. In contrast, there is normal embryonic testis development in Sox8 mutants which are initially fertile, but later develop progressive seminiferous tubule failure and infertility. To determine whether Sox9 is required for testis development after the initial steps of sex determination, we crossed Sox9(flox) mice with an AMH-Cre transgenic line thereby completely deleting Sox9 in Sertoli cells by E14.0. Conditional Sox9 null mutants show normal embryonic testis development and are initially fertile, but, like Sox8(-/-) mutants, become sterile from dysfunctional spermatogenesis at about 5 months. To see whether Sox8 may compensate for the absence of Sox9 during embryonic testis differentiation, we generated a Sox9 conditional knockout on a Sox8 mutant background. In the double mutants, differentiation of testis cords into seminiferous testis tubules ceases after P6 in the absence of one Sox8 allele, and after P0 in the absence of both Sox8 alleles, leading to complete primary infertility. Sox9,Sox8 double nullizygous testes show upregulation of early ovary-specific markers and downregulation of Sertoli intercellular junctions at E15.5. Their very low Amh levels still cause complete regression of the Müllerian duct but with reduced penetrance. This study shows that testis cord differentiation is independent of Sox9, and that concerted Sox9 and Sox8 function in post E14.0 Sertoli cells is essential for the maintenance of testicular function.

Developmental regulation of p70 S6 kinase by a G protein-coupled receptor dynamically modelized in primary cells.

The mechanisms whereby G protein-coupled receptors (GPCR) activate signalling pathways involved in mRNA translation are ill-defined, in contrast to tyrosine kinase receptors (TKR). We compared a GPCR and a TKR, both endogenously expressed, for their ability to mediate phosphorylation of 70-kDa ribosomal S6 kinase p70S6K in primary rat Sertoli cells at two developmental stages. In proliferating cells stimulated with follicle-stimulating hormone (FSH), active p70S6K was phosphorylated on T389 and T421/S424, through cAMP-dependent kinase (PKA) and phosphatidyl-inositide-3 kinase (PI3K) antagonizing actions. In FSH-stimulated differentiating cells, active p70S6K was phosphorylated solely on T389, PKA and PI3K independently enhancing its activity. At both developmental stages, insulin-induced p70S6K regulation was consistent with reported data. Therefore, TKR and GPCR trigger distinct p70S6K active conformations. p70S6K developmental regulation was formalized in a dynamic mathematical model fitting the data, which led to experimentally inaccessible predictions on p70S6K phosphorylation rate.

Sublethal exposure to deltamethrin impairs maternal egg care in the European earwig Forficula auricularia.

The application of pesticides typically leads to lethal and sublethal exposure of non-target insects. Whereas our current understanding of these sublethal effects typically focuses on reproductive and physiological parameters, recent works emphasize that sublethal effects on behaviors such as maternal care could be of major importance in non-target species. However, it remained unknown whether these sublethal effects occur in insects. Here, we tested if exposure to sublethal doses of deltamethrin - a pyrethroid insecticide commonly used in crops - alters the expression of maternal egg care in females of the European earwig Forficula auricularia, a predator insect and pest control. Our results first reveal that deltamethrin exposure impaired the expression of three forms of maternal egg care: It decreased the likelihood of mothers to gather their otherwise scattered clutch of eggs, increased the time during which the female abandoned the clutch after a predator attack and reduced egg grooming duration. These sublethal effects did not reflect a lower activity of deltamethrin-exposed females, as these females increased their expression of self-grooming, and deltamethrin exposure did not affect females' exploration and mobility. Finally, we found that the negative effects of deltamethrin on egg care did not modify egg development, hatching rate and juvenile weight, possibly due to the transient effects of deltamethrin on maternal behaviors. Overall, our results reveal that sublethal exposure to a pesticide may diminish maternal egg care in a natural pest control and call for the integration of this measurement in assays on pesticides application.

Phthalates impair germ cell development in the human fetal testis in vitro without change in testosterone production.

BACKGROUND: Several studies have described an increasing frequency of male reproductive disorders, which may have a common origin in fetal life and which are hypothesized to be caused by endocrine disruptors. Phthalate esters represent a class of environmental endocrine-active chemicals known to disrupt development of the male reproductive tract by decreasing testosterone production in the fetal rat. OBJECTIVES: Using the organ culture system we developed previously, we investigated the effects on the development of human fetal testis of one phthalate--mono-2-ethylhexyl phthalate (MEHP)--an industrial chemical found in many products, which has been incriminated as a disruptor of male reproductive function. METHODS: Human fetal testes were recovered during the first trimester (7-12 weeks) of gestation, a critical period for testicular differentiation, and cultured for 3 days with or without MEHP in basal conditions or stimulated with luteinizing hormone (LH). RESULTS: Whatever the dose, MEHP treatment had no effect on basal or LH-stimulated testosterone produced by the human fetal testis in vitro, although testosterone production can be modulated in our culture system. MEHP (10(-4) M) did not affect proliferation or apoptosis of Sertoli cells, but it reduced the mRNA expression of anti-Müllerian hormone. MEHP (10(-4) M) reduced the number of germ cells by increasing their apoptosis, measured by the detection of caspase-3-positive germ cells, without modification of their proliferation. CONCLUSIONS: This is the first experimental demonstration that phthalates alter the development of the germ cell lineage in humans. However, in contrast to results observed in the rat, phthalates did not affect steroidogenesis.

Sperm limitation affects sex allocation in a parasitoid wasp Nasonia vitripennis.

Insect reproduction is influenced by various external factors including temperature, a well-studied constraint. We investigated to what extent different levels of sperm limitation of males exposed to different heat stresses (34 and 36 °C) affect females' offspring production and sex allocation in Nasonia vitripennis. In this haplodiploid parasitoid wasp attacking different species of pest flies, we investigated the effect of the quantity of sperm females received and stored in their spermatheca on their sperm use decisions, hence sex allocation, over successive ovipositions. In particular, we compared the sex allocation of females presenting three levels of sperm limitation (i.e., mated with control, 34 °C heat-stressed or 36 °C heat-stressed males) on each host they parasitized. To disentangle the potential reduction of sperm quality after a heat stress exposure from that of sperm quantity, we also explored the clutch size and sex ratio produced by females that were partially sperm limited after copulating with multiply mated males. Independently of their sperm numbers, all types of females produced a similar total number of offspring, but the more limited ones had fewer daughters. Sperm limitation further affected the distribution of daughters' production across time. In addition to constraints acting on female physiology, male fertility should therefore be considered in studies measuring reproductive outputs of insects submitted to heat stresses.

Physiological and biochemical responses to thermal stress vary among genotypes in the parasitic wasp Nasonia vitripennis.

In ectotherm species such as insects, thermal fluctuations represent a major environmental factor driving development, survival and reproduction of individuals. Reproductive traits are particularly sensitive to heat stress that can induce a permanent sterility, or at least hypofertility, of adult males. This study aims to compare physiological and biochemical responses associated to male performances to an exposure of 24 h to moderately high temperature (36 °C) among three inbred lines of N. vitripennis (AsymC, Cor, Oul). Cor males showed very specific metabolic adjustments compared to the two other lines. By contrast, Oul males showed stronger phenotypic adjustment of its life cycle, and produced metabolic water to compensate water loss by heat stress. Finally, AsymC males had probably more difficulties to acclimate at 36 °C, even for a short period, as their adult longevity was significantly reduced. Thus, the ability of developmental plasticity in N. vitripennis males exposed to heat stress appears to be dependent of their genotypes.

High radiosensitivity of germ cells in human male fetus.

CONTEXT: Germ cells formed during human fetal life are essential for fertility of the adult, and several studies have described an increasing frequency of male reproductive disorders, which may have a common origin in fetal life and which are hypothesized to be caused by endocrine disruptors. However, factors inducing a genotoxic stress may also be implicated. OBJECTIVES: We investigated the effect of gamma-irradiation on the functions of human fetal testis during the first trimester of gestation by using an organ culture system. Then we focused on the role of the p53 pathway in the observed effects. RESULTS: Germ cells were highly sensitive to irradiation even at doses as low as 0.1 and 0.2 Gy. Indeed, for these doses, one third of germ cells died by apoptosis. Other germ cells were blocked in their cycle, but no repair seemed to occur, and longer culture with the highest dose used showed that they were destined to die. Sertoli cells were less affected, although their proliferation and the level of anti-Müllerian hormone were reduced. Irradiation had no effect on testosterone secretion or on the expression of steroidogenic enzymes by Leydig cells. After irradiation, p53 phosphorylated on serine 15 was detected from 1-24 h in all cell types. This activation of p53 was accompanied by an increase in mRNA levels of proapoptotic factors Bax and Puma, whereas that of antiapoptotic Bcl-2 remained unchanged. P21, which is responsible for cell cycle arrest, was also up-regulated 6, 30, and 72 h after irradiation. Finally, when we added pifithrin-alpha, a specific inhibitor of p53 functions, a significant decrease in irradiation-induced apoptosis in both germ and Sertoli cells was observed, indicating the involvement of the p53 pathway in irradiation-induced apoptosis. CONCLUSIONS: This study demonstrated here for the first time the great sensitivity of human fetal germ cells to genotoxic stress caused by ionizing radiation.

Dichlorodiphenyltrichloroethane impairs follicle-stimulating hormone receptor-mediated signaling in rat Sertoli cells.

Any toxicant that affects Sertoli cell development can potentially disturb male fertility. So far, the effects of organochlorine compounds have been poorly investigated in male. Here, we studied the effects of dichlorodiphenyltrichloroethane (DDT), an organochloride pesticide, on Sertoli cells. DDT inhibited the cAMP response to follicle-stimulating hormone (FSH), the major endocrine control of Sertoli cell development, and to a beta2-agonist, isoproterenol. DDT exposure decreased the level of FSH binding sites. Direct adenylyl cyclase activation by Forskolin was unaltered by DDT, while the activation of Galphas by cholera toxin was decreased by DDT. The DDT inhibitory effect on the FSH response was also observed in Ser W3 cells, a Sertoli cell-derived immortalized cell line. All these effects were reproduced by the lipophilic aromatic bisphenol A but not by structurally unrelated CisPlatin. In conclusion, these results are a first step in understanding the molecular basis of DDT deleterious effects in spermatogenesis.

[Does FSH signaling have a gender?]. / La signalisation FSH a-t-elle un sexe?

FSH is the main endocrine control of mammalian reproduction. FSH triggers somatic cells of the gonads which support germ cells metabolically, i.e. Sertoli cells of the seminiferous tubules, and granulosa cells harboring the oocyte, within the ovarian follicle. FSH leads to similar biological responses in both cell types since it stimulates proliferation and differentiation, according to the developmental stage. However, FSH receptor knock-out female mice are infertile, unlike male mice. Hence, FSH is not equally important in both sexes. Nevertheless, does FSH induce distinct signalling mechanisms in its target cells ? Here, we compare the signalling mechanisms induced by FSH in ovarian and testicular physiology.

Follicle-stimulating hormone activates p70 ribosomal protein S6 kinase by protein kinase A-mediated dephosphorylation of Thr 421/Ser 424 in primary Sertoli cells.

FSH is a major hormonal input that drives Sertoli cells to their fully differentiated function in male reproduction. It is a physiologically important issue to define how FSH mediates its effects at the cellular level to regulate gene expression. FSH biological activities are transduced via a seven-spanned transmembrane receptor, the FSH-R, primarily leading to cAMP-dependent protein kinase A (PKA) activation and cAMP response element binding protein-mediated transcriptional responses. Nevertheless, the intracellular mechanisms interacting with PKA to control Sertoli cell differentiation by FSH are still incompletely defined. Here, we report that, in primary cultures of Sertoli cells isolated from prepubertal rats, FSH enhanced p70S6K enzymatic activity, in a PKA-dependent manner. p70S6K was constitutively phosphorylated on Thr 389, in a manner sensitive to inhibitors of phosphatidyl-inositide-3 kinase and mammalian target of rapamycin. But FSH could not enhance p70S6K phosphorylation on Thr 389. Rather, the hormone induced the dephosphorylation of Thr 421/Ser 424, located in the autoinhibitory domain of p70S6K, in a PKA-dependent manner. Consistently, FSH-induced phosphorylation of the S6 ribosomal protein, a cellular substrate of p70S6K, required PKA activity. In conclusion, these results show that FSH triggers unexpected regulations of p70S6K by dephosphorylation of Thr 421/Ser 424 mediated by PKA, and stimulates S6 phosphorylation, in Sertoli cells.