Search

Sołtysik et al. show that the inner nuclear membrane of nonhepatocytes harbors triglyceride synthesis enzymes and generates nuclear lipid droplets (LDs). Seipin knockdown increases nuclear LDs through upregulating lipin-1β transcription and increasing phosphatidic acid levels in the nucleus., Nuclear lipid droplets (LDs) in hepatocytes are derived from precursors of very-low-density lipoprotein in the ER lumen, but it is not known how cells lacking the lipoprotein secretory function form nuclear LDs. Here, we show that the inner nuclear membrane (INM) of U2OS cells harbors triglyceride synthesis enzymes, including ACSL3, AGPAT2, GPAT3/GPAT4, and DGAT1/DGAT2, and generates nuclear LDs in situ. mTOR inhibition increases nuclear LDs by inducing the nuclear translocation of lipin-1 phosphatidic acid (PA) phosphatase. Seipin, a protein essential for normal cytoplasmic LD formation in the ER, is absent in the INM. Knockdown of seipin increases nuclear LDs and PA in the nucleus, whereas seipin overexpression decreases these. Seipin knockdown also up-regulates lipin-1β expression, and lipin-1 knockdown decreases the effect of seipin knockdown on nuclear LDs without affecting PA redistribution. These results indicate that seipin is not directly involved in nuclear LD formation but instead restrains it by affecting lipin-1 expression and intracellular PA distribution.

The origin and physiological significance of lipid droplets (LDs) in the nucleus is not clear. Here we show that nuclear LDs in hepatocytes are derived from apolipoprotein B (ApoB)-free lumenal LDs, a precursor to very low-density lipoproprotein (VLDL) generated in the ER lumen by microsomal triglyceride transfer protein. ApoB-free lumenal LDs accumulate under ER stress, grow within the lumen of the type I nucleoplasmic reticulum, and turn into nucleoplasmic LDs by disintegration of the surrounding inner nuclear membrane. Oleic acid with or without tunicamycin significantly increases the formation of nucleoplasmic LDs, to which CTP:phosphocholine cytidylyltransferase α (CCTα) is recruited, resulting in activation of phosphatidylcholine (PC) synthesis. Perilipin-3 competes with CCTα in binding to nucleoplasmic LDs, and thus, knockdown and overexpression of perilipin-3 increases and decreases PC synthesis, respectively. The results indicate that nucleoplasmic LDs in hepatocytes constitute a feedback mechanism to regulate PC synthesis in accordance with ER stress.

Objective Estrogen replacement therapy (ERT) for Turner syndrome (TS) is a widely discussed topic; however, the optimal model of ERT for patients with delayed diagnosis and/or initiation of therapy is still unclear, mainly due to insufficient data. We present the results of a prospective observational single-center study in which the efficacy of late-onset puberty induction by one-regimen transdermal ERT in TS girls was evaluated. Methods The analysis encompassed 49 TS girls (63.3% with 45,X) with hypergonadotropic hypogonadism in whom unified transdermal ERT protocol was used for puberty induction (first two months 12.5 μg/24 h, thereafter 25.0 μg/24 h until breakthrough bleeding). Clinical visits for examination and therapy modification took place every 3–6 months. Transabdominal pelvic ultrasound examinations were performed at least twice: at the beginning and at the end of follow-up. Results The mean (SD) age at ERT induction was 15.1 (1.3) years. The duration of follow-up was 2.4 (1.1) years. Half of all the patients had at least B2 after 0.57 years, B3 after 1.1 years, B4 after 1.97 years, and menarche after 1.82 years from ERT initiation. With earlier initiation of ERT (≤14 years), B2 (p = 0.059) was achieved faster and B4 (p = 0.018) significantly slower than with the later start of ERT. Thirty-four (94.4%) patients had at least stage B3 at menarche. The karyotype, initial weight, and body mass index had no impact on puberty tempo during ERT. The uterine volume increased significantly during ERT in all the study group (p 14 years). Conclusion The presented easy-to-use fixed-dose regimen for late-onset puberty induction allowed for a satisfactory rate of achieving subsequent puberty stages and did not influence the growth potential.

Although the nuclear action of estrogen receptors (ER) is a well-known fact, evidence supporting membrane estrogen receptors is steadily accumulating. New ER variants of unrecognized function have been discovered. ERα is a product of the ESR1 gene. It serves not only as a template for the full-length 66kDa protein, but also for smaller isoforms which exist as independent receptors. The recently discovered ERα36 (36kDa), consisting of 310 amino acids of total 595 ERα66 protein residues, is an example of that group. The transcription initiation site is identified in the first intron of the ESR1 gene. C-Terminal 27 amino acids are encoded by previously unknown exon 9. The presence of this unique C-terminal sequence creates an opportunity for the production of selective antibodies. ERα36 has been shown to have a high affinity to the cell membrane and as much as 90% of the protein can be bound with it. Post-translational palmitoylation is suspected to play a crucial role in ERα36 anchoring to the cell membrane. In silico analysis suggests the existence of a potential transmembrane domain in ERα36. ERα36 was found in most cells of animals at various ages, but its exact physiological function remains to be fully elucidated. It seems that cells traditionally considered as being deprived of ER are able to respond to hormonal stimulation via the ERα36 receptor. Moreover, ERα36 displays unique pharmacological properties and its action may be behind antiestrogen resistance. The use of ERα36 in cancer diagnosis gives rise to great expectations.

Objectives: Certain therapies with the use of analogs of gonadotropin-releasing hormone (GnRH, gonadoliberin) aim at achieving the effect of desensitization of the pituitary gland that causes inhibition of the hypothalamicpituitary-gonadal axis. The resulting hormonal changes may influence the location and expression of estrogen and progesterone receptors, as well as their endogenous functions. The aim: The aim of the study was to investigate whether long-term administration of low doses of dalarelin (GnRH agonist) and cetrorelix (GnRH antagonist) affected subcellular and tissue-specific location of ERα and ERβ estrogen receptors and progesterone receptor (PR) in rat uterus, as well as explore the extent to which the changes were reversible. Material and methods: Analogs were administered to SPD adult females in the course of 3 months, at a dose of 6 μg/kg b.w. Afterwards, the ovaries and the uterus were resected – in the course of 4 weeks after treatment completion. Tissue paraffin-embedded samples were stained with hematoxyline-eosin for morphological studies or incubated with specific antibodies for the immunohistochemical studies (ABC method). Results: GnRH analogs induced desensitization, resulting in specific and relatively persistent histological changes in the ovaries and the uterus. Strong nuclear reaction for ERα in the lining and the glandular epithelial cells in dalarelintreated rats, and lack of expression changes in cetrorelix-treated rats, were observed in the uterus. Epithelial ERα expressions were accompanied by diminished ERβ and elevated PR expression, as well as diminished ERα andERβ expression, and unchanged PR expression in the stromal and muscle cells, in both dalarelin- and cetrorelixtreatedrats. The majority of the changes were reversible after treatment discontinuation. Conclusions: Long-term exposure to low doses of GnRH analogs causes morphological changes in the uterine tissues, accompanied by reversible changes of the ERα, ERβ and PR expression, possibly influencing tissue sensitivity. These changes indicate that agonist and antagonist regulate ERα expression by means of different mechanisms. A functional interaction between the receptors, depending on ERβ expression, direct influence of analogs on the local hormonal axes, and dose-dependent effects, cannot be excluded. After discontinuation of the analog treatment, the time needed for stabilization of ER and PR expression is shorter than the period of time required to restore histological structure of the uterus.