Biology subjects

Enkler, L.

Publications and source records attributed to Enkler, L..

4 recordsLinked to original sources

bioRxiv2026

TORC1 spatial segregation and hysteresis are regulated by the small GTPase Arf1

TORC1 is a central regulator of growth, integrating inputs from kinases and signaling proteins. How TORC1 activity is regulated, is still not completely understood. The small GTPase Arf1 has been implicated in TORC1 regulation, but the underlying mechanism remains elusive. Here, we show that Arf1 controls TORC1 in an allele-specific manner under nutrient and heat stress in yeast. Unexpectedly, both the hyperactive mutant arf1-11 and the loss-of-function mutant arf1-18 reduce TORC1 activity, while other loss-of-function alleles did not. We reveal two distinct functions of Arf1: first, it ensures Golgi-to-vacuole/lysosome transport for the functional maintenance of these organelles; second, it regulates TORC1 activity at the ER-Golgi-vacuole interface. Hyperactive Arf1-11 drives sequestration of Kog1 and Tor1 into cytoplasmic foci, to which Arf1-11 can be equally recruited. Importantly, Arf1 also promotes TORC1 re-activation during stress recovery - so-called hysteresis. Our data reveal an unexpected dual function for Arf1 as a negative and a positive regulator of TORC1 activity in a context-dependent manner. TeaserThe small GPTase Arf1 acts as a dual switch for the key cellular growth regulator TORC1 by increasing or decreasing TORC1 activity depending on nutritional status and stress.

cell biology↗

bioRxiv2023

Ribosomal protein RPL39L is an efficiency factor in the cotranslational folding ofproteins with alpha helical domains

Increasingly many studies reveal how ribosome composition can be tuned to optimally translate the transcriptome of individual cell types. In this study, we investigated the expression pattern, structure within the ribosome and effect on protein synthesis of the ribosomal protein paralog 39L (RPL39L). With a novel mass spectrometric approach we have quantified the expression of RPL39L in human pluripotent cells, cancer cell lines and tissue samples, and in mouse germ cells. We generated RPL39L knock-out mouse embryonic stem cell (mESC) lines and demonstrated that RPL39L impacts the dynamics of translation, to support the pluripotency and differentiation, spontaneous and along the germ cell lineage. Most differences in protein abundance between WT and RPL39L KO lines were explained by widespread proteasomal activity. By CryoEM analysis of purified RPL39 and RPL39L-containing ribosomes we found that, unlike RPL39, RPL39L has two distinct conformations in the exposed segment of the nascent peptide exit tunnel, creating a distinct hydrophobic patch that has been predicted to support the efficient co-translational folding of alpha helices. Our study shows that ribosomal protein paralogs provide switchable modular components that can tune translation to the protein production needs of individual cell types.

molecular biology↗

bioRxiv2022

The small GTPase Arf1 regulates ATP synthesis and mitochondria homeostasis by modulating fatty acid metabolism

Lipid mobilization through fatty acid {beta}-oxidation is a central process essential for energy production during nutrient shortage. In yeast, this catabolic process starts in the peroxisome from where {beta}-oxidation products enter mitochondria and fuel the TCA cycle. Little is known about the physical and metabolic cooperation between these organelles. We found that expression of fatty acid transporters and of the rate-limiting enzyme involved in {beta}-oxidation are decreased in cells expressing a hyperactive mutant of the small GTPase Arf1, leading to an accumulation of fatty acids in lipid droplets. As a consequence, mitochondria became fragmented and ATP synthesis decreased. Genetic and pharmacological depletion of fatty acids phenocopied the arf1 mutant mitochondrial phenotype. Although {beta}-oxidation occurs mainly in mitochondria in mammals, Arf1s role in fatty acid metabolism is conserved. Together, our results indicate that Arf1 integrates metabolism into energy production by regulating fatty acid storage and utilization, and presumably organelle contact-sites.

cell biology↗

bioRxiv2018

Cex1 is a new component of the COPI Golgi-to-vacuole intracellular trafficking machinery

During translational elongation, aminoacylated tRNA are supplied to the ribosome by RNA-interacting proteins. Cex1, a HEAT-containing protein, has been shown to participate to this tRNA channeling by interacting with aminoacylated tRNA during their export from the nucleus. Here, we show that Cex1 is a component of COPI (coatomer complex I) coated vesicles involved in the Golgi-to-vacuole trafficking pathway in Saccharomyces cerevisiae. Cex1 interacts with key components of the COPI coat Sec27, Sec28 and Sec33 proteins. Moreover, fluorescent microscopy indicates that Cex1 is not localized at the nuclear periphery as expected for an effector of nuclear tRNA channeling, but is observed on endosomal trans-Golgi network (TGN) positive structures. This localization relies on the vacuolar protein sorting receptor Vps10. Our data not only resolve the functional ambiguity regarding Cex1 homologues across species, but also point to the possibility to develop yeast-based models to study neurodegenerative disorders linked to the Human Cex1 homologue SCYL1.

cell biology↗