Biology subjects

Ebert, K.

Publications and source records attributed to Ebert, K..

4 recordsLinked to original sources

bioRxiv2026

Sustained GnRH Agonism Alters Endocrine Dynamics and Pubertal Progression in Juvenile Rats

PurposeGonadotropin releasing hormone (GnRH) agonists are clinically used to delay pubertal progression by suppressing the hypothalamic-pituitary-gonadal (HPG) axis. While GnRH agonists have long been used clinically, the developmental characterization of HPG axis suppression during puberty remains incompletely understood. Thus, we examined the effects of GnRH receptor agonism in juvenile rats. HypothesisSustained GnRH receptor agonism will result in lower gonadal mass, blunt peripheral pubertal landmarks, and alter hormonal signaling dynamics within the HPG axis. MethodsAnimals received a single injection of extended-release leuprolide acetate depot (LA) or vehicle control on postnatal day (PND) 23. Animals were assessed for body mass and peripheral markers of puberty. On PND 44, animals were euthanized and tissues were evaluated to assess additional markers of pubertal maturation, pituitary gene transcript levels, and hormone concentrations in serum and gonads. ResultsIn females, LA treatment resulted in a smaller gonad size, increased body mass, and less vaginal openings. In males, LA treatment resulted in smaller gonads but did not significantly alter body mass or preputial separation. In the pituitary, LA-treated rats had lower Gnrhr, Fshb, and Lhb transcript levels regardless of sex, while females exhibited higher Cga and Nr5a1. Serum FSH and ACTH were lower in LA-treated animals, and treated females also had lower progestins and androstenedione, and higher LH. ConclusionsLA treatment reduced aspects of pubertal maturation and HPG axis output, with sex specific outcomes. These findings highlight the need for integrated, multi-level approaches to understand how altered GnRH signaling impacts pubertal and long-term physiology.

Developmental Biology↗

bioRxiv2025

Differential time-restricted sensitivity of enveloped viruses to Sec61 translocon blockade

The morphogenesis of enveloped viruses relies on the trafficking of transmembrane proteins through the secretory pathway to sites of virus envelopment. The first step in this pathway, their translocation into the endoplasmic reticulum, is therefore an attractive target for broad-spectrum intervention. Here, we tested if blockade of the Sec61 translocon by the Mycobacterium ulcerans exotoxin mycolactone, a potent inhibitor of Sec61, could block the production of virus glycoproteins and subsequent production of infectious virus from a range of human enveloped viruses: the DNA virus herpes simplex virus 1 (HSV1), and the RNA viruses, respiratory syncytial virus (RSV), influenza A virus (IAV), SARS coronavirus 2 (SARS CoV2) and Zika virus (ZIKV). In line with known translocation mechanisms, mycolactone blocked in vitro translocation and ectopic expression of type I transmembrane proteins but not type III, multipass or cytosolic proteins. Translocation of the type II protein RSV G was also blocked and although ectopically expressed G protein was detected, it was not glycosylated. Pretreatment of cells with mycolactone also blocked the synthesis of type I transmembrane proteins in infected cells and either the synthesis or glycosylation of type II transmembrane proteins, and the production of progeny from all viruses tested, while having no effect on virus entry or downstream synthesis of cytosolic proteins. While mycolactone treatment of HSV1 infected cells at various times after infection resulted in the immediate inhibition of virus production at the point of addition, IAV, RSV and ZIKV became resistant to the action of mycolactone surprisingly early in infection, and before virus glycoprotein synthesis was even detectable or virus production had begun. We therefore conclude that although inhibition of the translocation of virus transmembrane proteins through the Sec61 translocon can in principle block virus production, the morphogenesis of many enveloped RNA viruses requires only limited amounts of envelope proteins for successful propagation, providing novel insight into the biology of these viruses. Author SummaryMany circulating human pathogens are enveloped viruses that all use the cellular secretory pathway to target their envelope proteins to cellular sites of virus particle assembly. The potential to target this pathway could therefore offer a novel broad-spectrum therapy for existing, emerging and as yet unknown human pathogens. Here we have targeted the initial step in this pathway using a highly potent Sec61 inhibitor, mycolactone, to carry out the first comprehensive assessment of translocation disruption on a range of enveloped human viruses from different virus families, including herpes simplex virus, influenza A virus and SARS-CoV2. Our results have shown that Sec61 inhibition blocks the onward trafficking of many virus envelope proteins that are essential to produce infectious virus at assembly sites. However, unexpectedly, we found that several of the viruses were resistant to the effects of this toxin when it was added early in infection, indicating that the synthesis of these essential virus proteins occurs earlier in infection than previously recognised. Hence, while this approach may not be suitable as a broad intervention strategy, it has revealed new information on virus biology and provides us with a novel tool for exploring a wide range of enveloped viruses.

microbiology↗

bioRxiv2022

Kidins220 promotes thymic iNKT cell development by reducing TCR signals, but enhances TCR signals in splenic iNKT cells

The stepwise development of thymic invariant natural killer T (iNKT) cells is controlled by the TCR signal strength. The scaffold protein Kinase D interacting substrate of 220 kDa (Kidins220) binds to the TCR regulating TCR signaling. T cell-specific Kidins220 knock-out (T-KO) mice contain severely decreased iNKT numbers. Very early in iNKT development TCR signals are reduced in the T-KO. In later steps, TCR signaling is increased in the T-KO leading to enhanced apoptosis of iNKT cells. Kidins220s absence affects the iNKT1 subset most as it requires the weakest TCR signals for development. We also show that in iNKT1 development, weak TCR signals promote the progressive loss of CD4. In the periphery, Kidins220 switches its role back to promoting TCR signaling as splenic T-KO iNKT cells produce less cytokines and show reduced TCR signaling after in vivo stimulation with -galactosylceramide. In conclusion, Kidins220 promotes or inhibits TCR signaling depending on the developmental context. summary statementWe demonstrate that the transmembrane scaffold protein Kidins220 switches its role twice in iNKT cell biology: from a positive to a negative regulator of TCR signal strength during thymic development and back to a positive regulator in the periphery.

immunology↗

bioRxiv2019

Model-based analysis of response and resistance factors of cetuximab treatment in gastric cancer cell lines

Targeted cancer therapies are powerful alternatives to chemotherapies or can be used complementary to these. Yet, the response to targeted treatments depends on a variety of factors, including mutations and expression levels, and therefore their outcome is difficult to predict. Here, we develop a mechanistic model of gastric cancer to study response and resistance factors for cetuximab treatment. The model captures the EGFR, ERK and AKT signaling pathways in two gastric cancer cell lines with different mutation patterns. We train the model using a comprehensive selection of time and dose response measurements, and provide an assessment of parameter and prediction uncertainties. We demonstrate that the proposed model facilitates the identification of causal differences between the cell lines. Furthermore, our study shows that the model provides accurate predictions for the responses to different perturbations, such as knockdown and knockout experiments. Among other results, the model predicted the effect of MET mutations on cetuximab sensitivity. These predictive capabilities render the model a powerful basis for the assessment of gastric cancer signaling and for the development and discovery of predictive biomarkers.\n\nAuthor SummaryUnraveling the causal differences between drug responders and non-responders is an important challenge. The information can help to understand molecular mechanisms and to guide the selection and design of targeted therapies. Here, we approach this problem for cetuximab treatment for gastric cancer using mechanistic mathematical modeling. The proposed model describes multiple gastric cancer cell lines and can accurately predict the response in several validation experiments. Our analysis provides a differentiated view on mutations and explains, for instance, the relevance of MET mutations and the insignificance of PIK3CA mutation in the considered cell lines. The model might provide the basis for understanding the recent failure of several clinical studies.

systems biology↗