Eukaryotic initiation factor 5A plays an essential role in luteinizing hormone receptor regulation

Exposure to the phthalate metabolite MEHP impacts survival and growth of human ovarian follicles in vitro

Phthalates are found in everyday items like plastics and personal care products. There is an increasing concern that continuous exposure can adversely affect female fertility. However, experimental data are lacking to establish causal links between exposure and disease in humans. To address this gap, we tested the effects of a common phthalate metabolite, mono-(2-ethylhexyl) phthalate (MEHP), on adult human ovaries in vitro using an epidemiologically determined human-relevant concentration range (2.05 nM - 20.51 mM). Histomorphological assessments, steroid and cytokine measurements were performed on human ovarian tissue exposed to MEHP for 7 days in vitro. Cell viability and gene expression profile were investigated following 7 days of MEHP exposure using the human granulosa cancer cell lines KGN, and COV434, the germline tumor cell line PA-1, and human ovarian primary cells. Selected differentially expressed genes (DEGs) were validated by RT-qPCR and immunofluorescence in human ovarian tissue. MEHP exposure reduced follicular growth (20.51 nM) and increased follicular degeneration (20.51 mM) in ovarian tissue, while not affecting steroid and cytokine production. Out of the 691 unique DEGs identified across all the cell types and concentrations, CSRP2 involved in cytoskeleton organization and YWHAE as well as CTNNB1 involved in the Hippo pathway, were chosen for further validation. CSRP2 was upregulated and CTNNB1 downregulated in both ovarian tissue and cells, whereas YWHAE was downregulated in cells only. In summary, one-week MEHP exposure of human ovarian tissue can perturb the development and survival of human follicles through mechanisms likely involving dysregulation of cytoskeleton organization and Hippo pathway.

Identification of differentially expressed genes associated with precocious puberty by suppression subtractive hybridization in goat pituitary tissues

The aim of this study was to identify genes related to precocious puberty expressed in the pituitary of goats at different growth stages by suppression subtractive hybridization (SSH). The pituitary glands from Jining Gray (JG) goats (early puberty) and Liaoning Cashmere (LC) goats (late puberty) at 30, 90, and 180 days were used in this study. To identify differentially expressed genes (DEGs) in the pituitary glands, mRNA was extracted from these tissues, and SSH libraries were constructed and divided into the following groups: juvenile group (30-JG vs. 30-LC, API), puberty group (90-JG vs. 180-LC, BPI), and control group (90-JG vs. 90-LC, EPI). A total of 60, 49, and 58 DEGs were annotated by 222 Gene Ontology (GO) terms and 75 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Most of the DEGs were significantly enriched in GO terms related to 'structural constituent of ribosome', 'translation' and 'GTP binding', and numerous DEGs were also significantly enriched in KEGG terms related to the Jak-STAT signaling and oocyte meiosis pathways. Candidate genes associated with precocious puberty and sexual development were screened from the SSH libraries. These genes were analyzed to determine if they were expressed in the pituitary tissues of the goats at different growth stages and to identify genes that may influence the hypothalamic-pituitary-gonadal (HPG) axis. In this study, we found precocious puberty-related genes (such as PRLP0, EIF5A, and YWHAH) that may be interesting from an evolutionary perspective and that could be investigated for use in future goat breeding programs. Our results provide a valuable dataset that will facilitate further research into the reproductive biology of goats.

Regulation of gene expression by translation factor eIF5A: Hypusine-modified eIF5A enhances nonsense-mediated mRNA decay in human cells

Nonsense-mediated mRNA decay (NMD) couples protein synthesis to mRNA turnover. It eliminates defective transcripts and controls the abundance of certain normal mRNAs. Our study establishes a connection between NMD and the translation factor eIF5A (eukaryotic initiation factor 5A) in human cells. eIF5A modulates the synthesis of groups of proteins (the eIF5A regulon), and undergoes a distinctive two-step post-translational modification (hypusination) catalyzed by deoxyhypusine synthase and deoxyhypusine hydroxylase. We show that expression of NMD-susceptible constructs was increased by depletion of the major eIF5A isoform, eIF5A1. NMD was also attenuated when hypusination was inhibited by RNA interference with either of the two eIF5A modifying enzymes, or by treatment with the drugs ciclopirox or deferiprone which inhibit deoxyhypusine hydroxylase. Transcriptome analysis by RNA-Seq identified human genes whose expression is coordinately regulated by eIF5A1, its modifying enzymes, and the pivotal NMD factor, Upf1. Transcripts encoding components of the translation system were highly represented, including some encoding ribosomal proteins controlled by alternative splicing coupled to NMD (AS-NMD). Our findings extend and strengthen the association of eIF5A with NMD, previously inferred in yeast, and show that hypusination is important for this function of human eIF5A. In addition, they advance drug-mediated NMD suppression as a therapeutic opportunity for nonsense-associated diseases. We propose that regulation of mRNA stability contributes to eIF5A's role in selective gene expression.

LHCGR Expression During Follicle Stimulating Hormone-Induced Follicle Growth Is Negatively Regulated by Eukaryotic Initiation Factor 5A

We have shown that the transient changes in the expression of luteinizing hormone/choriogonadotropin receptor (LHCGR) messenger RNA (mRNA) during the ovarian cycle occurs, at least in part, through a posttranscriptional mechanism involving an LHCGR mRNA-binding protein (LRBP). Eukaryotic initiation factor 5A (eIF5A), an LRBP-interacting protein, participates in this process. eIF5A undergoes hypusination, a unique posttranslational modification that is necessary for its functions. This study examined the role of eIF5A in follicle-stimulating hormone (FSH)-induced LHCGR expression during follicular growth. Treatment of primary cultures of rat granulosa cells with FSH and 17β-estradiol (E2) showed a time-dependent increase in LHCGR mRNA expression. Conversely, inhibition of endogenous hypusination of eIF5A using N1-guanyl-1,7-diaminoheptane (GC7), a hypusination inhibitor, showed a greater increase in LHCGR mRNA expression over that produced by FSH and E2 alone. Further studies were carried out to determine the mechanism by which inhibition of hypusination of eIF5A causes an increase in LHCGR mRNA expression. Because LHCGR expression is negatively regulated by LRBP, the effect of inhibiting hypusination of eIF5A on LRBP expression was examined. The results showed a decrease in the expression of LRBP mRNA and protein when hypusination of eIF5A was inhibited by GC7. Because LRBP promotes LHCGR mRNA degradation, the results of this study support the notion that by inhibiting eIF5A hypusination, FSH reduces the expression of LRBP. This increases LHCGR mRNA expression by abrogating the inhibitory action of LRBP.

The Pathogenesis of Polycystic Ovary Syndrome (PCOS): The Hypothesis of PCOS as Functional Ovarian Hyperandrogenism Revisited

Polycystic ovary syndrome (PCOS) was hypothesized to result from functional ovarian hyperandrogenism (FOH) due to dysregulation of androgen secretion in 1989-1995. Subsequent studies have supported and amplified this hypothesis. When defined as otherwise unexplained hyperandrogenic oligoanovulation, two-thirds of PCOS cases have functionally typical FOH, characterized by 17-hydroxyprogesterone hyperresponsiveness to gonadotropin stimulation. Two-thirds of the remaining PCOS have FOH detectable by testosterone elevation after suppression of adrenal androgen production. About 3% of PCOS have a related isolated functional adrenal hyperandrogenism. The remaining PCOS cases are mild and lack evidence of steroid secretory abnormalities; most of these are obese, which we postulate to account for their atypical PCOS. Approximately half of normal women with polycystic ovarian morphology (PCOM) have subclinical FOH-related steroidogenic defects. Theca cells from polycystic ovaries of classic PCOS patients in long-term culture have an intrinsic steroidogenic dysregulation that can account for the steroidogenic abnormalities typical of FOH. These cells overexpress most steroidogenic enzymes, particularly cytochrome P450c17. Overexpression of a protein identified by genome-wide association screening, differentially expressed in normal and neoplastic development 1A.V2, in normal theca cells has reproduced this PCOS phenotype in vitro. A metabolic syndrome of obesity-related and/or intrinsic insulin resistance occurs in about half of PCOS patients, and the compensatory hyperinsulinism has tissue-selective effects, which include aggravation of hyperandrogenism. PCOS seems to arise as a complex trait that results from the interaction of diverse genetic and environmental factors. Heritable factors include PCOM, hyperandrogenemia, insulin resistance, and insulin secretory defects. Environmental factors include prenatal androgen exposure and poor fetal growth, whereas acquired obesity is a major postnatal factor. The variety of pathways involved and lack of a common thread attests to the multifactorial nature and heterogeneity of the syndrome. Further research into the fundamental basis of the disorder will be necessary to optimally correct androgen levels, ovulation, and metabolic homeostasis.

Hypusination of eukaryotic initiation factor 5A via cAMP-PKA-ERK1/2 pathway is required for ligand-induced downregulation of LH receptor mRNA expression in the ovary

Luteinizing hormone receptor (LHR) mRNA expression in the ovary is regulated post-transcriptionally by an LH receptor mRNA binding protein (LRBP). Eukaryotic initiation factor 5A (EIF5A), identified as an LRBP-interacting protein plays a crucial role in LHR mRNA expression. In this study, we have demonstrated that during hCG-induced LHR downregulation, a significant upregulation of eIF5A mRNA expression and hypusination of eIF5A protein occurs in a time dependent manner. Pretreatment with H89, a specific inhibitor of PKA, and U0126, a specific inhibitor of ERK1/2 significantly inhibited both hCG-induced eIF5A mRNA expression and hypusination of eIF5A protein. Pretreatment with GC7, a specific inhibitor of eIF5A hypusination significantly abolished hCG-induced LRBP mRNA and protein expression. Furthermore, GC7 pretreatment significantly inhibited hCG-induced interaction of LRBP with LHR mRNA as assessed by RNA electrophoretic mobility gel shift assay (REMSA). GC7 treatment also reversed LHR mRNA downregulation. Taken together, these results suggest that hCG-induced LHR mRNA downregulation is mediated by cAMP-PKA-ERK1/2 signaling leading to activation of eIF5A hypusination.