Inhibition of ribosome biogenesis in the epidermis is sufficient to trigger organism-wide growth quiescence independently of nutritional status in C. elegans

Uncoupling overeating and fat storage by modulation of different serotonergic receptors

Psychotropic drugs such as antipsychotics improve symptoms of psychiatric disorders. However, they are associated with severe metabolic side effects that remodel energy balance, resulting in weight gain and increased food intake (hyperphagia). Here, we compare how antipsychotics and exogenous serotonin induce hyperphagia by remodeling energy balance. We find that the ability of serotonin and antipsychotics to remodel energy balance strictly depends on the serotonergic receptors SER-7 and SER-5, respectively. While both molecules induce hyperphagia, serotonin does so by increasing energy expenditure and reducing fat stores. In contrast, antipsychotics block the inhibitory effect of fat storage on feeding, thereby inducing hyperphagia and increasing fat stores. Thus, it is possible to manipulate energy balance to induce hyperphagia while either increasing or decreasing fat storage. Inactivation of the germline remodels energy balance similar to antipsychotic treatment, promoting hyperphagia while increasing fat storage. Consistent with overlapping mechanisms, antipsychotics are no longer able to remodel energy balance in both C. elegans and mice lacking an intact germline. Thus, our results uncouple overeating from fat storage and show that overeating can be induced by mechanisms that reduce or increase fat stores.

Differential impacts of ribosomal protein haploinsufficiency on mitochondrial function

The interplay between ribosomal protein (RP) composition and mitochondrial function is essential for energy homeostasis. Balanced RP production optimizes protein synthesis while minimizing energy costs, but its impact on mitochondrial functionality remains unclear. Here, we investigated haploinsufficiency for RP genes (rps-10, rpl-5, rpl-33, and rps-23) in Caenorhabditis elegans and corresponding reductions in human lymphoblast cells. Significant mitochondrial morphological differences, upregulation of glutathione transferases, and SKN-1-dependent oxidative stress resistance were observed across mutants. Loss of a Datasingle rps-10 copy reduced mitochondrial activity, energy levels, and oxygen consumption, mirrored by similar reductions in mitochondrial activity and energy levels in lymphoblast cells with 50% lower RPS10 transcripts. Both systems exhibited altered translation efficiency (TE) of mitochondrial electron transport chain components, suggesting a conserved mechanism to adjust mitochondrial protein synthesis under ribosomal stress. Finally, mitochondrial membrane and cytosolic RPs showed significant RNA and TE covariation in lymphoblastoid cells, highlighting the interplay between protein synthesis machinery and mitochondrial energy production.

Localization and expression dynamics of an RNA Pol I core subunit in response to fasting in C. elegans

Nutrient availability influences ribosome biogenesis, requiring dynamic regulation of RNA Pol I activity. In C. elegans , fasting reduces pre-rRNA levels. However, whether this reduction stems from a regulation of RNA Pol I expression remains unclear. Here, we examined how the nutritional status affects the localization and expression levels of RPOA-2 , a core subunit of RNA Pol I, in the intestine. We found that RPOA-2 retains its nucleolar localization regardless of animals being fed, fasted or fed after fasting. Interestingly, fasting reduces RPOA-2 protein amounts which are restored upon feeding. These findings suggest that the availability of RNA Pol I core subunits contributes to the regulation of rDNA transcription in response to nutrients.

Fasting shapes chromatin architecture through an mTOR/RNA Pol I axis

Chromatin architecture is a fundamental mediator of genome function. Fasting is a major environmental cue across the animal kingdom, yet how it impacts three-dimensional (3D) genome organization is unknown. Here we show that fasting induces an intestine-specific, reversible and large-scale spatial reorganization of chromatin in Caenorhabditis elegans. This fasting-induced 3D genome reorganization requires inhibition of the nutrient-sensing mTOR pathway, acting through the regulation of RNA Pol I, but not Pol II nor Pol III, and is accompanied by remodelling of the nucleolus. By uncoupling the 3D genome configuration from the animal's nutritional status, we find that the expression of metabolic and stress-related genes increases when the spatial reorganization of chromatin occurs, showing that the 3D genome might support the transcriptional response in fasted animals. Our work documents a large-scale chromatin reorganization triggered by fasting and reveals that mTOR and RNA Pol I shape genome architecture in response to nutrients.

[TSR2 overexpression inhibits proliferation and invasion of gastric cancer cells by downregulating the PI3K/AKT signaling pathway]

OBJECTIVE

To investigate the expression of TSR2 in gastric cancer and explore its correlation with progression of gastric cancer and the possible mechanism.

METHODS

We retrospectively analyzed TSR2 expression in clinical specimens from 105 gastric cancer patients and the impact of TSR2 expression level on disease progression and 5-year postoperative survival of the patients. GO and KEGG enrichment analyses were used to predict the biological functions and mechanisms of TSR2. In gastric cancer MGC-803 cells with lentivirus-mediated TSR2 overexpression or knockdown, the changes in cell proliferation, invasion, and migration were assessed with CCK-8 and Transwell assays, and the expressions of p-PI3K and p-AKT were detected using Western blotting.

RESULTS

TSR2 expression was significantly lower in gastric cancer tissues than in the adjacent tissues with significant correlations with CEA level, CA19-9 level, and T and N staging (P < 0.05). A low TSR2 expression, CEA≥5 μg/L, CA19-9≥37 kU/L, T3-T4 stages, and N2-N3 staged were identified as independent risk factors affecting 5-year survival rate of the patients following radical surgery (P < 0.05), and a high TSR2 expression was associated with a higher 5-year survival rate of the patients (P < 0.001). Bioinformatics analysis suggested the functional involvement of TSR2 with the PI3K/AKT signaling pathway. MGC-803 cells overexpressing TSR2 showed significantly lowered proliferation, migration, and invasion capacities (P < 0.05), while TSR2 knockdown produced the opposite effects (P < 0.05). Western blotting showed that TSR2 overexpression reduced the phosphorylation of PI3K and AKT, and TSR2 knockdown caused the opposite changes in MGC-803 cells (P < 0.05).

CONCLUSION

TSR2 is lowly expressed in gastric cancer tissues to adversely affect the patients' prognosis, and its overexpression inhibits gastric cancer cell proliferation, invasion, and migration possibly by downregulating the PI3K/AKT pathway.

Cytosolic Ribosomal Protein Haploinsufficiency affects Mitochondrial Morphology and Respiration

The interplay between ribosomal protein composition and mitochondrial function is essential for sustaining energy homeostasis. Precise stoichiometric production of ribosomal proteins is crucial to maximize protein synthesis efficiency while reducing the energy costs to the cell. However, the impact of this balance on mitochondrial ATP generation, morphology and function remains unclear. Particularly, the loss of a single copy ribosomal protein gene is observed in Mendelian disorders like Diamond Blackfan Anemia and is common in somatic tumors, yet the implications of this imbalance on mitochondrial function and energy dynamics are still unclear. In this study, we investigated the impact of haploinsufficiency for four ribosomal protein genes implicated in ribosomopathy disorders (rps-10, rpl-5, rpl-33, rps-23) in Caenorhabditis elegans and corresponding reductions in human lymphoblast cells. Our findings uncover significant, albeit variably penetrant, mitochondrial morphological differences across these mutants, alongside an upregulation of glutathione transferases, and SKN-1 dependent increase in oxidative stress resistance, indicative of increased ROS production. Specifically, loss of a single copy of rps-10 in C. elegans led to decreased mitochondrial activity, characterized by lower energy levels and reduced oxygen consumption. A similar reduction in mitochondrial activity and energy levels was observed in human leukemia cells with a 50% reduction in RPS10 transcript levels. Importantly, we also observed alterations in the translation efficiency of nuclear and mitochondrial electron transport chain components in response to reductions in ribosomal protein genes' expression in both C. elegans and human cells. This suggests a conserved mechanism whereby the synthesis of components vital for mitochondrial function are adjusted in the face of compromised ribosomal machinery. Finally, mitochondrial membrane and cytosolic ribosomal components exhibited significant covariation at the RNA and translation efficiency level in lymphoblastoid cells across a diverse group of individuals, emphasizing the interplay between the protein synthesis machinery and mitochondrial energy production. By uncovering the impact of ribosomal protein haploinsufficiency on the translation efficiency of electron transport chain components, mitochondrial physiology, and the adaptive stress responses, we provide evidence for an evolutionarily conserved strategy to safeguard cellular functionality under genetic stress.