Biology subjects

Cezanne, A.

Publications and source records attributed to Cezanne, A..

7 recordsLinked to original sources

bioRxiv2026

Bridging the lipid divide: archaeal ESCRT-III binds phosphoinositol and polarises the cytokinetic membrane

All cells remodel their membranes to divide. The highly conserved ESCRT-III system forms contractile polymers which, through direct interactions with membrane lipids, remodel membranes across the tree of life. In exploring how ESCRT-III divides the chemically and structurally unique archaeal membrane, we reveal that the homologue CdvB1 is required for the establishment of a distinct membrane domain within the division bridge of Sulfolobus acidocaldarius, associated with an accumulation of membrane-spanning inositol phosphate lipids. We show that CdvB1 associates with phosphoinositides in vitro and that this interaction aids cytokinesis in vivo. Together, we suggest that although eukaryotes inherited their membrane lipids from bacteria during eukaryogenesis, key features of the ESCRT-III:membrane interface that allow these polymers to bind, organise, and remodel eukaryotic membranes, may originate in archaea.

cell biology↗

bioRxiv2026

A green fluorescent protein for live imaging in hyperthermophiles

Hyperthermophiles, organisms that thrive at temperatures above 60 {degrees}C, have played important roles in biotechnology and promise to reveal new biology. However, how these cells live remains poorly understood in part due to the lack of bright, thermostable fluorescent proteins that can be used to study protein localisation and dynamics at high temperatures. To overcome this challenge, here we describe the development of "Matcha", a green fluorescent protein that we have engineered from Thermal Green Protein by directed evolution in the thermophilic archaeon Sulfolobus acidocaldarius. The screen identified 7 mutations that when combined led to an [~]50-fold increase in the brightness of Matcha in vivo at physiological temperatures. Since this is sufficient for live cell imaging, we were then able to use Matcha-fusion proteins to study the division ring dynamics in Sulfolobus. Remarkably, this analysis reveals that, while ESCRT-III rings are disassembled as cells complete division, CdvA forms a stable polymeric ring that persists, and is asymmetrically inherited by one of the two daughter cells following cytokinesis. This study highlights the power of Matcha as a tool to shed light on our understanding of the cell biology of hyperthermophiles.

cell biology↗

bioRxiv2025

Temporal and spatial coordination of DNA segregation and cell division in an archaeon.

Cells must coordinate DNA segregation with cytokinesis to ensure that each daughter cell inherits a complete genome. Here, we explore how DNA segregation and division are mechanistically coupled in archaeal relatives of eukaryotes, which lack CDK/Cyclins. Using live cell imaging we first describe the series of sequential changes in DNA organisation that accompany cell division in Sulfolobus, which computational modelling shows likely aid genome segregation. Through a perturbation analysis we identify a regulatory checkpoint which ensures that the compaction of the genome into two spatially segregated nucleoids only occurs once cells have assembly a division ring - which also defines the axis of DNA segregation. Finally, we show that DNA compaction and segregation depends, in part, on a ParA homologue, SegA, and its partner SegB, whose absence leads to bridging DNA. Taken together, these data show how regulatory checkpoints like those operating in eukaryotes aid high-fidelity division in an archaeon.

cell biology↗

bioRxiv2025

The mechanics of a continuous self-assembling surface-layer aids cell division in an archaeon

The surface layer or "S-layer" is a planar lattice of glycosylated proteins that coats a wide range of archaea and bacteria instead of a classical cell wall or capsular polysaccharides, insulating them from the extracellular space and providing the cell membrane with physical support. Although the S-layers role as a mechanical support for the membrane might be expected to hinder cell division, we show that in rapidly dividing Sulfolobus acidocaldarius cells, the S-layer protein SlaA self-assembles into flexible lattice that helps flattens the cytokinetic furrow to accelerate ESCRT-III dependent cell division - a role that is especially important under conditions of mechanical stress. Taken together, these results generated using mutational analysis, live and fixed cellular imaging, along with electron cryomicroscopy, define the rules governing S-layer self-assembly and show how the mechanical properties of flexible lattice coats can enhance membrane functions to both physically support a cell and help to drive ESCRT-III dependent cell division. Significance statementThe bounding membrane of a cell must be protected from environmental insults. In many bacteria and archaea that lack a cell wall, this is achieved by an enveloping S-layer. By virtue of its rigid, planar structure, the S-layer is also expected to act as a barrier to the cell shape changes required for cytokinesis. In this study of the S-layer lattice in the archaeon Sulfolobus acidocaldarius however, we demonstrate a role for this self-assembling mechanical support in re-shaping the cytokinetic furrow as an aid to ESCRT-III-mediated division. In showing how mechanically active and passive structures can work together to give rise to mechanically stable cells that can divide, this reconciles what seems like a trade-off between resilience and flexibility.

molecular biology↗

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↗

bioRxiv2019

A non-linear system patterns Rab5 GTPase on the membrane

Proteins can self-organize into spatial patterns via non-linear dynamic interactions on cellular membranes. Modelling and simulations have shown that small GTPases can generate patterns by coupling guanine nucleotide exchange factors (GEF) to effector binding, generating a positive feedback of GTPase activation and membrane recruitment. Here, we reconstituted the patterning of the small GTPase Rab5 and its GEF/effector complex Rabex5/Rabaptin5 on supported lipid bilayers as a model system for membrane patterning. We show that there is a "handover" of Rab5 from Rabex5 to Rabaptin5 upon nucleotide exchange. A minimal system consisting of Rab5, RabGDI and a complex of full length Rabex5/Rabaptin5 was necessary to pattern Rab5 into membrane domains. Surprisingly, a lipid membrane composition mimicking that of the early endosome was required for Rab5 patterning. The prevalence of GEF/effector coupling in nature suggests a possible universal system for small GTPase patterning involving both protein and lipid interactions.

biochemistry↗

bioRxiv2019

Allosteric structural alterations and auto-regulation of Rab5 GEF activity in Rabex5

Intracellular trafficking depends on the function of Rab GTPases, whose activation is regulated by guanine exchange factors (GEFs). The Rab5 GEF, Rabex5, was previously proposed to be autoinhibited by its C-terminus. Here, we studied full-length Rabex5 and Rabaptin5 proteins as well as domain deletion Rabex5 mutants using hydrogen deuterium exchange mass spectrometry. We generated a structural model of Rabex5, using chemical crosslinking mass spectrometry and integrative modeling techniques. Our results are inconsistent with the previous model of autoinhibition. By correlating structural changes with nucleotide exchange activity for each construct, we uncovered new auto-regulatory roles for the Ubiquitin binding domains and the Linker connecting those domains to the catalytic core of Rabex5. Our results suggest a more complex auto-regulation mechanism than previously thought and imply that Ubiquitin binding serves not only to position Rabex5 but to also control its Rab5 GEF activity through allosteric structural alterations.

biophysics↗