Biology subjects

Evergren, E.

Publications and source records attributed to Evergren, E..

4 recordsLinked to original sources

bioRxiv2025

Plasma membrane rather than endosomal Gq signaling drives transcriptional activity by the viral chemokine receptor US28 in glioblastoma

US28 is a human cytomegalovirus-encoded chemokine receptor homologue that has high agonist-independent activity, internalizes constitutively, and plays an oncomodulatory role in glioblastoma. As G protein signaling was originally believed to strictly occur at the plasma membrane, it has been assumed that US28s constitutive Gq/11 signaling is mediated by a minor population at the plasma membrane. However, accumulating evidence shows that some GPCRs activate G proteins from intracellular organelles, such as endosomes. Importantly, endosomal rather than plasma membrane G protein signaling has been associated with transcriptional activity. Here, we demonstrate that the endosomal US28 population robustly activates Gq/11, and thus, provides the major contribution of Gq/11 signaling. Surprisingly, US28 signaling at the plasma membrane rather than from endosomes primarily drives upregulation of gene expression involved in cell proliferation and inflammatory responses that are associated with glioblastoma and cancer. Our findings highlight the crucial role of receptor signaling location in cellular responses.

cell biology↗

bioRxiv2023

Ultrastructural analysis of prostate cancer tissue provides insights into androgen-dependent adaptations to membrane contact site establishment

Membrane trafficking and organelle contact sites are important for regulating cell metabolism and survival; processes often deregulated in cancer. Prostate cancer is the second leading cause of cancer-related death in men in the developed world. While early-stage disease is curable by surgery or radiotherapy there is an unmet need to identify prognostic biomarkers, markers to treatment response and new therapeutic targets in intermediate-late stage disease. This study explored the morphology of organelles and membrane contact sites in tumor tissue from normal, low and intermediate histological grade groups. The morphology of organelles in secretory prostate epithelial cells; including Golgi apparatus, ER, lysosomes; was similar in prostate tissue samples across a range of Gleason scores. Mitochondrial morphology was not dramatically altered, but the number of membrane contacts with the ER notably increased with disease progression. A three-fold increase of tight mitochondria-ER membrane contact sites was observed in the intermediate Gleason score group compared to normal tissue. To investigate whether these changes were concurrent with an increased androgen signaling in the tissue, we investigated whether an anti-androgen used in the clinic to treat advanced prostate cancer (enzalutamide) could reverse the phenotype. Patient-derived explant tissues with an intermediate Gleason score were cultured ex vivo in the presence or absence of enzalutamide and the number of ER-mitochondria contacts were quantified for each matched pair of tissues. Enzalutamide treated tissue showed a significant reduction in the number and length of mitochondria-ER contact sites, suggesting a novel androgen-dependent regulation of these membrane contact sites. This study provides evidence for the first time that prostate epithelial cells undergo adaptations in membrane contact sites between mitochondria and the ER during prostate cancer progression. These adaptations are androgen-dependent and provide evidence for a novel hormone-regulated mechanism that support establishment and extension of MAMs. Future studies will determine whether these changes are required to maintain pro-proliferative signaling and metabolic changes that support prostate cancer cell viability.

cancer biology↗

bioRxiv2023

The E3 ubiquitin ligase Itch regulates death receptor and cholesterol trafficking to affect TRAIL-mediated apoptosis

The activation of apoptosis signalling by TRAIL (TNF-related apoptosis-inducing ligand) through receptor binding is a fundamental mechanism of cell death induction and is often perturbed in cancer cells to enhance their cell survival and treatment resistance. Ubiquitination plays an important role in the regulation of TRAIL-mediated apoptosis, and here we investigate the role of the E3 ubiquitin ligase Itch in TRAIL-mediated apoptosis in oesophageal cancer cells. Knockdown of Itch expression resulted in resistance to TRAIL-induced apoptosis, caspase-8 activation, Bid cleavage and also promoted cisplatin resistance. Whilst the assembly of the death-inducing signalling complex (DISC) at the plasma membrane was not perturbed relative to the control, the TRAIL-R2 receptor was mis-localised in the Itch-knockdown cells. Further, we observed significant mitochondrial widening with an increased cholesterol content. An inhibitor of cholesterol trafficking, U18666A, was able to replicate some of the effects of Itch knockdown, including protection from TRAIL-induced apoptosis, reduced caspase-8 activation, Bid cleavage and Cisplatin resistance. This study highlights the importance of Itch in regulating the crosstalk between mitochondrial cholesterol and TRAIL-induced apoptosis.

cell biology↗

bioRxiv2019

Regulation of FLIP(L) and TRAIL-R2 signalling by the SCFSkp2 Ubiquitin Ligase Complex

Depending on its expression levels, the long splice form of the pseudo-caspase FLIP (FLIP(L)) can act as an inhibitor (high expression) or activator (low expression) of apoptosis induction by the TRAIL-R2 death-inducing signalling complex (DISC); its expression levels are therefore tightly regulated. Here, we demonstrate that the Skp1-Cullin-1-F-box (SCF) Cullin-Ring E3 Ubiquitin Ligase complex containing Skp2 (SCFSkp2) regulates the stability of FLIP(L) (but not the short splice form FLIP(S)), and, unusually, this is mediated by direct binding of FLIP(L) to Cullin-1 rather than via Skp2. By fine mapping the interaction of FLIP(L) with Cullin-1 to the large subunit of its pseudo-caspase domain, we found that the interaction is significantly stronger with FLIP(L)s DISC-processed p43-form. Importantly, this interaction disrupts the ability of p43-FLIP to interact with FADD, caspase-8 and another DISC component, TRAF2. Moreover, we find that SCFSkp2 associates with TRAIL-R2 constitutively and does so independently of FLIP(L) and other canonical DISC components. Inhibition of Cullin-1 expression (using siRNA) or activity (using a NEDDylation inhibitor, MLN4924) enhanced FLIP(L) and TRAF2 levels at the TRAIL-R2 DISC and enhanced caspase-8 processing. This suggests that processing of FLIP(L) to p43-FLIP at the TRAIL-R2 DISC enhances its interaction with co-localised SCFSkp2, leading to disruption of p43-FLIPs association with the DISC thereby altering caspase-8 processing. These findings provide important new insights into how FLIP(L) expression and TRAIL-R2 signaling is controlled.

molecular biology↗