Biology subjects

Rospert, S.

Publications and source records attributed to Rospert, S..

3 recordsLinked to original sources

bioRxiv2026

Regulation of protein abundance in neurons by selective translation of 3'UTR isoforms

The precise regulation of protein synthesis is essential for cellular function and survival. In particular, in neurons, dysregulated mRNA translation is linked to impaired memory formation and is a hallmark of neurodegenerative diseases. Neurons are characterized by tissue-specific, long 3' untranslated regions (3'UTRs); in this study, we demonstrate that mRNA isoforms with these neuronal 3'UTRs are less efficiently translated than their short counterparts in Drosophila and mammalian brains. 3'UTR-dependent translation is based on a negative feedback mechanism centered around the two neural-enriched proteins ELAV and Pumilio. The long elav 3'UTR inhibits production of the neuronal ELAV protein, which in turn mediates 3'UTR extension of hundreds of neuronal genes. Those long 3'UTR isoforms are preferentially bound and translationally inhibited by Pumilio. The regulatory loop maintains optimal neuronal 3'UTR and protein levels in conditions of genetic and environmental perturbations; its disruption reduces animal viability and lowers stress resilience, and causes severe developmental phenotypes in flies and in human brain organoids. We propose 3'UTR-mediated translational control as an evolutionarily conserved mechanism for the maintenance of cell-type-specific proteostasis.

molecular biology↗

bioRxiv2022

Snf1/AMPK fine-tunes TORC1 signaling in response to glucose starvation

The AMP-activated protein kinase (AMPK) and the target of rapamycin complex 1 (TORC1) are central kinase modules of two opposing signaling pathways that control eukaryotic cell growth and metabolism in response to the availability of energy and nutrients. Accordingly, energy depletion activates AMPK to inhibit growth, while nutrients and high energy levels activate TORC1 to promote growth. Both in mammals and lower eukaryotes such as yeast, the AMPK and TORC1 pathways are wired to each other at different levels, which ensures homeostatic control of growth and metabolism. In this context, a previous study (Hughes Hallet et. al, 2015) reported that AMPK in yeast, i.e. Snf1, plays a role in short-term downregulation of TORC1 activity upon acute glucose starvation, but the underlying mechanism has remained elusive. Using a combination of unbiased mass spectrometry (MS)-based phosphoproteomics, genetic, biochemical, and physiological experiments, we show here that Snf1 contributes to glucose starvation-induced short-term TORC1 inactivation primarily through the TORC1-regulatory protein Pib2. Our data, therefore, extend the function of Pib2 to a hub that integrates both glucose and, as reported earlier, glutamine signals to control TORC1. We further demonstrate that Snf1 phosphorylates the TORC1 effector kinase Sch9 within its N-terminal region and thereby antagonizes the phosphorylation of a C-terminal TORC1-target residue within Sch9 itself that is critical for its activity. The consequences of Snf1-mediated phosphorylation of Pib2 and Sch9 are physiologically additive and sufficient to explain the role of Snf1 in short-term inhibition of TORC1 in acutely glucose-starved cells.

biochemistry↗

bioRxiv2021

Quantitative proteomics identifies the universally conserved ATPase Ola1p as a positive regulator of heat shock response in Saccharomyces cerevisiae

The universally conserved P-loop ATPase Ola1 is implicated in various cellular stress response pathways, as well as in cancer and tumor progression. However, Ola1p functions are divergent between species and the involved mechanisms are only poorly understood. Here, we studied the role of Ola1p in the heat shock response of the yeast Saccharomyces cerevisiae using a combination of quantitative and pulse labeling-based proteomics approaches, in vitro studies and cell-based assays. Our data show that when heat stress is applied to cells lacking Ola1p, the expression of stress-protective proteins is enhanced. During heat stress Ola1p associates with detergent-resistant protein aggregates and rapidly forms assemblies that localize to stress granules. The assembly of Ola1p was also observed in vitro using purified protein and conditions, which resembled those in living cells. We show that loss of Ola1p results in increased protein ubiquitination of detergent-insoluble aggregates recovered from heat-shocked cells. When subsequently cells lacking Ola1p were relieved from heat stress, reinitiation of translation was delayed, whereas, at the same time, de novo synthesis of central factors required for protein refolding and the clearance of aggregates was enhanced when compared to wildtype cells. The combined data suggest that upon acute heat stress, Ola1p is involved in the stabilization of misfolded proteins, which become sequestered in cytoplasmic stress granules. This function of Ola1p enables cells to resume translation in a timely manner as soon as heat stress is relieved.

cell biology↗