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Azione Molecolare E Cellulare Degli Ormoni Della Riproduzione
No full textClassicamente, la segnalazione dipendente dall’attivazione del cAMP mediata dal recettore dell'ormone follicolo-stimolante (FSHR) e dal recettore dell'ormone luteinizzante (LH) (LHCGR) favorisce la crescita del follicolo ovarico umano e la maturazione degli ovociti. Tuttavia, esistono dati in vitro contraddittori che suggeriscono un diverso significato fisiologico della segnalazione di cAMP mediata da FSHR, mostrando allo stesso tempo l'attivazione di eventi steroidogenici e pro-apoptotici. Questi segnali possono essere alterati dagli estrogeni che inducono eventi anti-apoptotici attraverso i loro recettori nucleari e all'azione non genomica di un recettore degli estrogeni accoppiato a proteine G (GPER). Lo scopo del progetto è chiarire il ruolo degli estrogeni/gonadotropine e dei loro recettori di membrana nella regolazione della fisiologia ovarica e nella selezione del follicolo dominante. In questo studio è stato dimostrato che GPER forma dimeri sia con FSHR che con LHCGR sulla superficie cellulare di cellule HEK293 che sovraesprimono i due recettori e di cellule primarie della granulosa luteina umana (hGLC). Gli eteromeri FSHR/GPER riprogrammano i segnali del cAMP e di morte, in stimoli proliferativi fondamentali per sostenere la sopravvivenza degli ovociti. Nelle cellule della granulosa umana, i segnali di sopravvivenza mancano quando è presente un rapporto FSHR:GPER elevato, che influisce negativamente sulla maturazione del follicolo e si correla con l'accoppiamento preferenziale alla proteina Gαs, l’attivazione della via cAMP/PKA e la capacità di risposta ad FSH dei pazienti sottoposti a stimolazione ovarica controllata. Gli eteromeri FSHR/GPER, invece, mediano segnali anti-apoptotici e proliferativi dipendenti da FSH tramite il dimero Gβγ e la compromissione della formazione degli eteromeri o il knockdown GPER aumenta la morte cellulare e la steroidogenesi FSH-dipendenti. Al contrario, il complesso GPER/LHCGR non influenza la produzione di cAMP indotta da LH e hCG e non compromette l'attivazione della via cAMP/PKA. Ciò si evince dalla simile fosforilazione di CREB ed ERK1/2 e dalla stessa produzione di progesterone in hGLC trattate con siRNA contro GPER e quelle trattato con mock. È interessante notare che GPER riduce l’accoppiamento LHCGR/Gαq e di conseguenza impedisce il rilascio intracellulare di Ca2+ e l'accumulo di IP1, dopo stimolazione con LH e hCG, in cellule HEK293 che co-esprimono LHCGR e GPER rispetto alle cellule che esprimono solo LHCGR. Inoltre, è stato dimostrato che in presenza di GPER la cinetica dell'internalizzazione di FSHR attraverso endosomi precoci e tardivi è ridotta, suggerendo la sua capacità di bloccare FSHR a livello intracellulare e riducendo il riciclaggio di FSHR sulla membrana. Infatti, l'internalizzazione di FSHR è necessaria affinché GPER inibisca la risposta del cAMP indotta da FSH. Secondo i nostri risultati, gli estrogeni sono selettivamente coinvolti nella regolazione dei segnali pro e anti-apoptotici, nell'internalizzazione dei recettori attraverso i complessi FSHR/GPER e nella modulazione della cascata di segnali mediata da LHCGR. I nostri risultati indicano come la maturazione degli ovociti dipenda dalla capacità del GPER di modulare i segnali selettivi di FSHR e LHCGR, indicando che gli eteromeri dei recettori delle gonadotropine possono essere un marker della proliferazione cellulare.Classically, follicle-stimulating hormone receptor (FSHR) and luteinizing hormone (LH) receptor (LHCGR) -driven cAMP-mediated signaling boosts human ovarian follicle growth and oocyte maturation. However, contradicting in vitro data suggest a different view on physiological significance of FSHR-mediated cAMP signalling, showing at the same time the activation of steroidogenic and pro-apoptotic events. These signals can be impaired by estrogens inducing anti-apoptotic events via nuclear receptors and non-genomic action of a G protein-coupled estrogen receptor (GPER). The aim of the project is to better understand the role of estrogens/gonadotropins and their membrane receptors in regulating ovarian physiology and the selection of the dominant follicle. In this study it was demonstrated that GPER heteromerizes both with FSHR and LHCGR at the cell surface of HEK293 cells overexpressing the two receptors as well as human primary granulosa lutein cells (hGLC). FSHR/GPER heteromers reprogram cAMP/death signals into proliferative stimuli fundamental for sustaining oocyte survival. In human granulosa cells, survival signals are missing at high FSHR:GPER ratio, which negatively impacts follicle maturation and strongly correlates with preferential Gαs protein/cAMP-pathway coupling and FSH responsiveness of patients undergoing controlled ovarian stimulation. In contrast, FSHR/GPER heteromers triggered anti-apoptotic/proliferative FSH signaling delivered via the Gβγ dimer, whereas impairment of heteromer formation or GPER knockdown enhanced the FSH-dependent cell death and steroidogenesis. On the other hand, GPER/LHCGR complex does not affect the LH and hCG-induced cAMP production and do not compromise the activation of the cAMP/PKA pathway, as it is indicated by similar CREB and ERK1/2 phosphorylation and same progesterone production in hGLC treated with siRNA against GPER, and the mock-treated one. Interestingly, GPER displace the LHCGR/Gαq coupling and consequently impedes the intracellular Ca2+ release and IP1 accumulation in LHCGR-GPER co-expressing HEK293 cells upon LH and hCG treatment compared to LHCGR-expressing cells. Also, it was demonstrated that in presence of GPER the kinetic of FSHR internalization through early and late endosomes is reduced, suggesting its ability to blockade FSHR at the intracellular level and reduce FSHR recycling on cell membrane. Indeed, FSHR internalization is necessary for GPER to inhibit FSH-induced cAMP response. According to our results, estrogens are selectively involved in the regulation of pro- and anti-apoptotic signals and receptor internalization through FSHR/GPER complexes and in modulation of LHCGR-mediated signaling cascade. Our findings indicate how oocyte maturation depends on the capability of GPER to shape FSHR and LHCGR selective signals, indicating hormone receptor heteromers may be a marker of cell proliferation
G protein‐coupled receptor–receptor interactions in gonadal physiology
No full textBackground: Gonadotropins are glycoprotein hormones fundamental in the endocrine regulation of reproduction. They act on structurally similar members of G protein-coupled receptors (GPCRs) expressed exclusively in the gonads and support gametogenesis, sex steroid synthesis, and pregnancy. While it is a common opinion that the gonadotropin receptors act as a single molecule entity (monomer), increasing evidence underlines the formation of molecular complexes involving multiple receptors. Objectives: To review current knowledge of membrane receptor-receptor interactions in reproduction. Results and Discussion: Homo/heteromers of gonadotropin receptors may act as allosteric modulators, act as biased agonist and/or cooperate in sustaining intracellular signals fundamental to support reproduction. Technical limitations lead to in vitro data that require to be confirmed in vivo to figure out the physiological impact of gonadotropin receptor assemblies. Conclusions: Gonadotropin receptor homo/heteromers provide a new field of research that deserves attention for possible clinical and therapeutic implications in physiology and pathophysiology
The cAMP/PKA pathway: steroidogenesis of the antral follicular stage.
No full textPituitary gonadotropins, follicle-stimulating (FSH) and luteinizing hormone (LH) promote follicular recruitment and support antral follicle growth, maturation and selection, resulting in ovulation of the dominant follicle. FSH and LH biological functions are mediated by G protein-coupled receptors, FSHR and LHCGR, resulting in the activation of a number of signaling cascades, such as the cyclic AMP/protein kinase A (cAMP/PKA) pathway. Some in-vitro data are consistent with the dual, proliferative and pro-apoptotic role of cAMP, leaving unanswered questions on how cAMP/PKA signaling is linked to the follicle fate. Progression of the antral stage is characterized by the presence of dynamic serum gonadotropin and estrogen levels, accompanying proliferation and steroidogenesis of growing as well as apoptosis of atretic follicles. These events are parallel to changes of FSHR and LHCGR density at the cell surface occurring throughout the antral stage, reasonably modulating the cAMP/PKA activation pattern, cell metabolism and functions. Understanding whether gonadotropins and receptor expression levels impact on the steroidogenic pathway and play a role in determining the follicular fate, may put new light on molecular mechanisms regulating human reproduction. The aim of the present review is to update the role of major players modulating the cAMP/PKA pathway and regulating the balance between proliferative, differentiating and pro-apoptotic signals
Allosteric modulation of gonadotropin receptors
Full text linkGonadotropins regulate reproductive functions by binding to G protein-coupled receptors (FSHR and LHCGR) expressed in the gonads. They activate multiple, cell-specific signalling pathways, consisting of ligand-dependent intracellular events. Signalling cascades may be modulated by synthetic compounds which bind allosteric sites of FSHR and LHCGR or by membrane receptor interactions. Despite the hormone binding to the orthosteric site, allosteric ligands, and receptor heteromerizations may reshape intracellular signalling pattern. These molecules act as positive, negative, or neutral allosteric modulators, as well as non-competitive or inverse agonist ligands, providing a set of new compounds of a different nature and with unique pharmacological characteristics. Gonadotropin receptor allosteric modulation is gathering increasing interest from the scientific community and may be potentially exploited for clinical purposes. This review summarizes the current knowledge on gonadotropin receptor allosteric modulation and their potential, clinical use
L’ormone luteinizzante e la gonadotropina corionica umana: attività molecolari e cliniche mediate da un unico recettore
No full textIn vitro analysis of FSHR internalization and signalling mediated by two different FSH preparations
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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