Biology subjects

Hurtig, F.

Publications and source records attributed to Hurtig, F..

6 recordsLinked to original sources

bioRxiv2022

The patterned assembly and stepwise Vps4-mediated disassembly of composite ESCRT-III polymers drives archaeal cell division

ESCRT-III family proteins form composite polymers that deform and cut membrane tubes in the context of a wide range of cell biological processes across the tree of life. In reconstituted systems sequential changes in the composition of ESCRT-III polymers induced by the AAA ATPase Vps4 have been shown to remodel membranes. However, it is not known how composite ESCRT-III polymers are organised and remodelled in space and time in cells. Here, taking advantage of the relative simplicity of the ESCRT-III-dependent division system in Sulfolobus acidocaldarius, one of the closest experimentally tractable prokaryotic relative of eukaryotes, we use super-resolution microscopy and computational modelling to show how CdvB/CdvB1/CdvB2 proteins form a precisely patterned composite ESCRT-III division ring which undergoes stepwise Vps4-dependent disassembly and contracts to cut cells into two. These observations lead us to suggest sequential changes in a patterned composite polymer as a general mechanism of ESCRT-III-dependent membrane remodelling.

cell biology↗

bioRxiv2021

Physical mechanisms of ESCRT-III-driven cell division in archaea

Living systems propagate by undergoing rounds of cell growth and division. Cell division is at heart a physical process that requires mechanical forces, usually exerted by protein assemblies. Here we developed the first physical model for the division of archaeal cells, which despite their structural simplicity share machinery and evolutionary origins with eukaryotes. We show how active geometry changes of elastic ESCRT-III filaments, coupled to filament disassembly, are sufficient to efficiently split the cell. We explore how the non-equilibrium processes that govern the filament behaviour impact the resulting cell division. We show how a quantitative comparison between our simulations and dynamic data for ESCRTIII-mediated division in Sulfolobus acidocaldarius, the closest archaeal relative to eukaryotic cells that can currently be cultured in the lab, and reveal the most likely physical mechanism behind its division.

biophysics↗

bioRxiv2020

Heimdallarchaea encodes profilin with eukaryotic-like actin regulation and polyproline binding

The evolutionary events which led to the first eukaryotic cell are still controversial1-4. The Asgard genome encodes a variety of eukaryotic signature proteins previously unseen in prokaryotes. Functional and structural characterization of these proteins is beginning to shed light on the complexity and pedigree of the ancestral eukaryotic cell5,6. In eukaryotes, the key cytoskeletal protein actin is important for diverse cellular processes such as membrane remodeling and cell motility7. Dynamic polymerization of actin provides both structure and generates the force which drives motility and membrane remodeling. These processes demand rapid filament assembly and disassembly on microsecond timescales. In eukaryotes, a variety of highly adapted proteins including gelsolin, profilin, VASP, ARP2/3 and signaling molecules (Phosphatidylinositol-4,5-bisphosphate (PIP2)) are crucial for organizing cellular cytoskeleton dynamics. Amongst others, the Asgard genomes encode predicted putative profilin homologues that regulate eukaryotic actin polymerization in vitro5,8. Interestingly, Asgard profilins appear to be regulated by PIP2, but not by polyproline rich motifs which are important for recruitment of actin:profilin complexes in eukaryotes5,9. These findings indicate that the Asgard archaea may have possessed analogous membrane organization to present-day eukaryotes, but that polyproline-mediated profilin regulation may have emerge later in the eukaryotic lineage5. Here, we show that Heimdallarchaeota, a candidate phylum within the Asgard superphylum, encodes a putative profilin (heimProfilin) that interacts with PIP2 and is regulated by polyproline motifs, implicative of an origin predating the rise of the eukaryotes. Additionally, we provide evidence for a novel regulatory mechanism whereby an extended N-terminal loop abolishes PIP2 and polyproline interactions. Lastly, we provide the first evidence for actin polymerization of an Asgard actin homologue. In context, these findings provide further evidence for the existence of a complex cytoskeleton already in Last eukaryotic common ancestor (LECA).

evolutionary biology↗

bioRxiv2020

NMR backbone assignment and dynamics of Profilin from Heimdallarchaeota

The origin of the eukaryotic cell is an unsettled scientific question. The Asgard superphylum has emerged as a compelling target for studying eukaryogenesis due to the previously unseen diversity of eukaryotic signature proteins. However, our knowledge about these proteins is still relegated to metagenomic data and very little is known about their structural properties. Additionally, it is still unclear if these proteins are functionally homologous to their eukaryotic counterparts. Here, we expressed, purified and structurally characterized profilin from Heimdallarchaeota in the Asgard superphylum. The structural analysis shows that while this profilin possess similar secondary structural elements as eukaryotic profilin, it contains additional secondary structural elements that could be critical for its function and an indication of divergent evolution.

biophysics↗

bioRxiv2019

Proteasome-mediated protein degradation resets the cell division cycle and triggers ESCRT-III-mediated cytokinesis in an archaeon

The archaeon Sulfolobus acidocaldarius is a relative of eukaryotes known to progress orderly through its cell division cycle despite lacking obvious CDK/cyclin homologues. Here, in exploring the mechanisms underpinning archaeal cell division cycle control, we show that the proteasome of S. acidocaldarius, like its eukaryotic counterpart, regulates the transition from the end of one cell division cycle to the beginning of the next. Further, we identify the archaeal ESCRT-III homologue CdvB as a key target of the proteasome, and show that state-dependent degradation of CdvB triggers archaeal cell division by allowing constriction of a CdvB1:CdvB2 ESCRT-III division ring. These findings suggest an ancient role for proteasome-mediated degradation in resetting the cell division cycle in both archaea and eukaryotes.

cell biology↗

bioRxiv2018

NanoJ: a high-performance open-source super-resolution microscopy toolbox

Super-resolution microscopy has become essential for the study of nanoscale biological processes. This type of imaging often requires the use of specialised image analysis tools to process a large volume of recorded data and extract quantitative information. In recent years, our team has built an open-source image analysis framework for super-resolution microscopy designed to combine high performance and ease of use. We named it NanoJ - a reference to the popular ImageJ software it was de-veloped for. In this paper, we highlight the current capabilities of NanoJ for several essential processing steps: spatio-temporal alignment of raw data (NanoJ-Core), super-resolution image re-construction (NanoJ-SRRF), image quality assessment (NanoJ-SQUIRREL), structural modelling (NanoJ-VirusMapper) and control of the sample environment (NanoJ-Fluidics). We expect to expand NanoJ in the future through the development of new tools designed to improve quantitative data analysis and measure the reliability of fluorescent microscopy studies.

bioinformatics↗