Ref HAL: hal-05322104_v1
Exporter : BibTex | endNote

Ref HAL: hal-04953347_v1
DOI: 10.1016/j.str.2025.01.005
Exporter : BibTex | endNote
Résumé:

Cytoskeletal-mediated membrane compartmentalization is essential to support cellular functions, from signaling to cell division, migration, or phagocytosis. Septins are cytoskeletal proteins that directly interact with membranes, acting as scaffolds to recruit proteins to cellular locations and as structural diffusion barriers. How septins interact with and remodel the lipid organization of membranes is unclear. Here, we combined minimal reconstituted systems and yeast cell imaging to study septin-mediated membrane organization. Our results show that at low concentrations membrane-diffusive septins self-assemble into sub-micrometric patches that co-exist with the septin collar at the division site. We found that patches are made of short septin filaments and that are able to modulate the lipid organization of membranes. Furthermore, we show that the polybasic domain of Cdc11 influences the membrane-organizing and curvature-sensing properties of septins. Collectively, our work provides understanding of the molecular mechanisms by which septins can support cellular functions intimately linked to membranes.

Ref HAL: hal-04783895_v1
Exporter : BibTex | endNote
Résumé:

Egress of malaria merozoites from infected red blood cells (iRBC) is a critical step in the parasite’s life cycle. The egress is accompanied by the formation of a pore in the erythrocyte membrane, followed by an outward curling of the membrane around the pore, resulting in a complete eversion of the erythrocyte membrane, pushing the parasites away. Despite the well-documented steps of the egress, the detailed mechanism and source of energy for such a spectacular eversion of iRBC remains largely unknown. In this paper, we consider a biophysical model based on the energetics of the egress process that includes both viscous dissipation and energy consumption for the formation of the rim around the pore in iRBC. We show that viscosity does not play a significant role in iRBC eversion and we hypothesize that this process is controlled by lateral lipid diffusion. The model is supported by quantitative estimates and is in good agreement with known experimental data.

Ref HAL: hal-04878189_v1
Exporter : BibTex | endNote

Ref HAL: hal-04878180_v1
Exporter : BibTex | endNote

Ref HAL: hal-04741167_v2
Exporter : BibTex | endNote
Résumé:

Commentaires: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in (citation of published article) and may be found at https://doi.org/10.1063/5.0236067

Ref HAL: hal-04890444_v1
Ref Arxiv: 2307.00636
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

The cooperative binding of molecular agents onto a substrate is pervasive in living systems. To study whether a system shows cooperativity, one can rely on a fluctuation analysis of quantities such as the number of substrate-bound units and the residence time in an occupancy state. Since the relative standard deviation from the statistical mean monotonically decreases with the number of binding sites, these techniques are only suitable for small enough systems, such as those implicated in stochastic processes inside cells. Here, we present a general-purpose grand canonical Hamiltonian description of a small one-dimensional (1D) lattice gas with either nearest-neighbor or long-range interactions as prototypical examples of cooperativity-influenced adsorption processes. First, we elucidate how the strength and sign of the interaction potential between neighboring bound particles on the lattice determine the intensity of the fluctuations of the mean occupancy. We then employ this relationship to compare the theoretical predictions of our model to data from single molecule experiments on bacterial flagellar motors (BFM) of E. coli. In this way, we find evidence that cooperativity controls the mechano-sensitive dynamical assembly of the torque-generating units, the so-called stator units, onto the BFM. Furthermore, in an attempt to quantify fluctuations and the adaptability of the BFM, we estimate the stator-stator interaction potential. Finally, we conclude that the system resides in a sweet spot of the parameter space (phase diagram) with characteristics suitable for a smoothly and widely adaptive system, while minimizing fluctuations.