A regulator of G protein signaling, RGS3, inhibits gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone (LH) secretion

Exploring the expression and preliminary function of chicken regulator of G protein signalling 3 (RGS3) gene in follicular development

1. The following study explored the expression and preliminary function of RGS3. The spatial and temporal expression patterns of the RGS3 gene were analysed in the ovarian stroma of Shendan No. 6 Green shell hens and Hy-line Brown hens at four time points (6, 28, 40 and 52 weeks old), as well as in various organs and follicles of Hy-line Brown hens.2. Based on the genomic and protein sequences of RGS3 in NCBI database, phylogenetic trees were constructed using MEGA-X. The protein interaction network was analysed using STRING. According to the results of protein-protein interaction network and pathways, the mRNA expression levels of RGS3 and three interaction proteins were explored by qRT-PCR in vitro.3. Spatio-temporal expression data revealed that RGS3 mRNA was expressed in all the organs tested, being highest in the hypothalamus. In different follicles, RGS3 mRNA was highly expressed in post-ovulatory follicles, followed by ovarian stroma and large white follicles. The expression levels of RGS3 mRNA in the ovarian stroma were significantly higher in Shendan No. 6 Green shell hens than that in the Hy-line Brown hens at all egg-laying stages.4. The phylogenetic tree results showed that ducks, geese and chickens had higher homology based on the genomic and protein sequence of RGS3. Moreover, chicken RGS3 interacted with GSK3B, RAF1 and BRAF based on STRING prediction. In vitro follicle stimulating hormone (FSH) treatment showed that mRNA expression levels of RGS3 and those of its predicted interacting proteins BRAF and GSK3B decreased with increasing FSH concentration. The results suggested that RGS3 responds to FSH and may play an important role in the regulation follicular development in chicken.

Regulators of G protein signaling in cardiovascular function during pregnancy

G protein-coupled receptor signaling mechanisms are implicated in many aspects of cardiovascular control, and dysfunction of such signaling mechanisms is commonly associated with disease states. Investigators have identified a large number of regulator of G protein signaling (RGS) proteins that variously contribute to the modulation of intracellular second-messenger signaling kinetics. These many RGS proteins each interact with a specific set of second-messenger cascades and receptor types and exhibit tissue-specific expression patterns. Increasing evidence supports the contribution of RGS proteins, or their loss, in the pathogenesis of cardiovascular dysfunctions. This review summarizes the current understanding of the functional contributions of RGS proteins, particularly within the B/R4 family, in cardiovascular disorders of pregnancy including gestational hypertension, uterine artery dysfunction, and preeclampsia.

Different expression patterns of sperm motility-related genes in testis of diploid and tetraploid cyprinid fish†

Sperm motility is an important standard to measure the fertility of male. In our previous study, we found that the diploid spermatozoa from allotetraploid hybrid (4nAT) had longer durations of rapid and slow progressive motility than haploid spermatozoa from common carp (COC). In this study, to explore sperm motility-related molecular mechanisms, we compared the testis tissues transcriptomes from 2-year-old male COC and 4nAT. The RNA-seq data revealed that 2985 genes were differentially expressed between COC and 4nAT, including 2216 upregulated and 769 downregulated genes in 4nAT. Some differentially expressed genes, such as tubulin genes, dynein, axonemal, heavy chain(dnah) genes, mitogen-activated protein kinase(mapk) genes, tektin 4, FOX transcription factors, proteasome genes, and ubiquitin carboxyl-terminal hydrolase(uchl) genes, are involved in the regulation of cell division, flagellar and ciliary motility, gene transcription, cytoskeleton, energy metabolism, and the ubiquitin–proteasome system, suggesting that these genes were related to sperm motility of the 4nAT. We confirmed the differential expression of 12 such genes in 4nAT by quantitative PCR. By western blotting, we also confirmed increased expression of Uchl3 in 4nAT testis. In addition, we identified 1915 and 2551 predicted long noncoding RNA (lncRNA) transcripts from testis tissue transcriptomes of COC and 4nAT, respectively. Of these, 1575 lncRNAs were specifically expressed in 4nAT and 939 were specifically expressed in COC. This study provides insights into the transcriptome profile of testis tissues from diploid and tetraploid, which are useful for research on regulatory mechanisms behind sperm motility in male polyploidy.

RGS3 controls T lymphocyte migration in a model of Th2-mediated airway inflammation

T cell migration toward sites of antigen exposure is mediated by G protein signaling and is a key function in the development of immune responses. Regulators of G protein signaling (RGS) proteins modulate G protein signaling; however, their role in the regulation of adaptive immune responses has not been thoroughly explored. Herein we demonstrated abundant expression of the Gi/Gq-specific RGS3 in activated T cells, and that diminished RGS3 expression in a T cell thymoma increased cytokine-induced migration. To examine the role of endogenous RGS3 in vivo, mice deficient in the RGS domain (RGS3(ΔRGS)) were generated and tested in an experimental model of asthma. Compared with littermate controls, the inflammation in the RGS3(ΔRGS) mice was characterized by increased T cell numbers and the striking development of perivascular lymphoid structures. Surprisingly, while innate inflammatory cells were also increased in the lungs of RGS3(ΔRGS) mice, eosinophil numbers and Th2 cytokine production were equivalent to control mice. In contrast, T cell numbers in the draining lymph nodes (dLN) were reduced in the RGS3(ΔRGS), demonstrating a redistribution of T cells from the dLN to the lungs via increased RGS3(ΔRGS) T cell migration. Together these novel findings show a nonredundant role for endogenous RGS3 in controlling T cell migration in vitro and in an in vivo model of inflammation.

The role of Mitogen activated protein kinase (MAPK) in sperm functions

The generation of mature spermatozoa in the epididymis includes the activation of the MAPK cascade in a complex manner. MAPKs are thought to be involved in the regulation of transcription and ectoplasmic specialization (ES) in the testis. MAPKs also regulate mature spermatozoa flagellar motility, hyperactivation and the acrosome reaction. Here we review the current data regarding the functions of MAPKs in spermatogenesis and in mature spermatozoa.

Signaling by G-protein-coupled receptor (GPCR): studies on the GnRH receptor

Gonadotropin-releasing hormone (GnRH) is the first key hormone of reproduction. GnRH analogs are extensively used in in vitro fertilization, and treatment of sex hormone-dependent cancers, due to their ability to bring about 'chemical castration'. The interaction of GnRH with its cognate type I receptor (GnRHR) in pituitary gonadotropes results in the activation of Gq/G(11), phospholipase Cbeta (PLCbetaI), PLA(2), and PLD. Sequential activation of the phospholipases generates the second messengers inositol 1, 4, 5-trisphosphate (IP(3)), diacylglycerol (DAG), and arachidonic acid (AA), which are required for Ca(2+) mobilization, the activation of various protein kinase C isoforms (PKCs), and the production of prostaglandin (PG) and other metabolites of AA, respectively. PKC isoforms are the major mediators of the downstream activation of a number of mitogen-activated protein kinase (MAPK) cascades by GnRH, namely: extracellular signal-regulated kinase (ERK), jun-N-terminal kinase (JNK), and p38MAPK. The activated MAPKs phosphorylate both cytosolic and nuclear proteins to initiate the transcriptional activation of the gonadotropin subunit genes and the GnRHR. While Ca(2+) mobilization has been found to initiate rapid gonadotropin secretion, Ca(2+), together with various PKC isoforms, MAPKs and AA metabolites also serve as key nodes, in the GnRH-stimulated signaling network that enables the gonadotropes to decode GnRH pulse frequencies and translating that into differential gonadotropin synthesis and release. Even though pulsatility of GnRH is recognized as a major determinant for differential gonadotropin subunit gene expression and gonadotropin secretion very little is yet known about the signaling circuits governing GnRH action at the 'Systems Biology' level. Direct apoptotic and metastatic effects of GnRH analogs in gonadal steroid-dependent cancers expressing the GnRHR also seem to be mediated by the activation of the PKC/MAPK pathways. However, the mechanisms dictating life (pituitary) vs. death (cancer) decisions made by the same GnRHR remain elusive. Understanding these molecular mechanisms triggered by the GnRHR through biochemical and 'Systems Biology' approaches would provide the basis for the construction of the dynamic connectivity maps, which operate in the various cell types (endocrine, cancer, and immune system) targeted by GnRH. The connectivity maps will open a new vista for exploring the direct effects of GnRH analogs in tumors and the design of novel combined therapies for fertility control, reproductive disorders and cancers.

Regulation of Smad-mediated gene transcription by RGS3

Regulator of G protein signaling (RGS) proteins are united into a family by the presence of the homologous RGS domain that binds the alpha subunits of heterotrimeric G proteins and accelerates their GTPase activity. A member of this family, RGS3 regulates the signaling mediated by G(q) and G(i) proteins by binding the corresponding Galpha subunits. Here we show that RGS3 interacts with the novel partners Smad2, Smad3, and Smad4-the transcription factors that are activated through a transforming growth factor-beta (TGF-beta) receptor signaling. This interaction is mediated by the region of RGS3 outside of the RGS domain and by Smad's Mad homology 2 domain. Overexpression of RGS3 results in inhibition of Smad-mediated gene transcription. RGS3 does not affect TGF-beta-induced Smad phosphorylation, but it prevents heteromerization of Smad3 with Smad4, which is required for transcriptional activity of Smads. This translates to functional inhibition of TGF-beta-induced myofibroblast differentiation by RGS3. In conclusion, this study identifies a novel, noncanonical role of RGS3 in regulation of TGF-beta signaling through its interaction with Smads and interfering with Smad heteromerization.

RGS16 is a negative regulator of SDF-1-CXCR4 signaling in megakaryocytes

Regulators of G-protein signaling (RGS) constitute a family of proteins involved in the negative regulation of signaling through heterotrimeric G protein-coupled receptors (GPCRs). Several RGS proteins have been implicated in the down-regulation of chemokine signaling in hematopoietic cells. The chemokine stromal-cell-derived factor 1 (SDF-1) activates migration of hematopoietic progenitors cells but fails to activate mature megakaryocytes despite high levels of CXC chemokine receptor 4 (CXCR4) receptor expression in these cells. This prompted us to analyze RGS expression and function during megakaryocyte differentiation. We found that RGS16 and RGS18 mRNA expression was up-regulated during this process. Overexpressing RGS16 mRNA in the megakaryocytic MO7e cell line inhibited SDF-1-induced migration, mitogen-activated protein kinase (MAPK) and protein kinase B (AKT) activation, whereas RGS18 overexpression had no effect on CXCR4 signaling. Knocking down RGS16 mRNA via lentiviral-mediated RNA interference increased CXCR4 signaling in MO7e cells and in primary megakaryocytes. Thus, our data reveal that RGS16 is a negative regulator of CXCR4 signaling in megakaryocytes. We postulate that RGS16 regulation is a mechanism that controls megakaryocyte maturation by regulating signals from the microenvironment.

Identification of Ser153 in ICL2 of the gonadotropin-releasing hormone (GnRH) receptor as a phosphorylation-independent site for inhibition of Gq coupling

Type I gonadotropin-releasing hormone (GnRH) receptor (GnRHR) is unique among mammalian G-protein-coupled receptors (GPCRs) in lacking a C-terminal tail, which is involved in desensitization in GPCRs. Therefore, we searched for inhibitory sites in the intracellular loops (ICLs) of the GnRHR. Synthetic peptides corresponding to the three ICLs were inserted into permeabilized alphaT3-1 gonadotrope cells, and GnRH-induced inositol phosphate (InsP) formation was determined. GnRH-induced InsP production was potentiated by ICL2 > ICL3 but not by the ICL1 peptides, suggesting they are acting as decoy peptides. We examined the effects of six peptides in which only one of the Ser or Thr residues was substituted with Ala or Glu. Only substitution of Ser153 with Ala or Glu ablated the potentiating effect upon GnRH-induced InsP elevation. ERK activation was enhanced, and the rate of GnRH-induced InsP formation was about 6.5-fold higher in the first 10 min in COS-1 cells that were transfected with mutants of the GnRHR in which the ICL2 Ser/Thr residues (Ser151, Ser153, and Thr142) or only Ser153 was mutated to Ala as compared with the wild type GnRHR. The data indicate that ICL2 harbors an inhibitory domain, such that exogenous ICL2 peptide serves as a decoy for the inhibitory site (Ser153) of the GnRHR, thus enabling further activation. GnRH does not induce receptor phosphorylation in alphaT3-1 cells. Because the phosphomimetic ICL2-S153E peptide did not mimic the stimulatory effect of the ICL2 peptide, the inhibitory effect of Ser153 operates through a phosphorylation-independent mechanism.