Biology subjects

Bershadsky, A.

Publications and source records attributed to Bershadsky, A..

7 recordsLinked to original sources

bioRxiv2025

Redeployment of Archaeal ESCRT Systems Reveals Conserved Mechanisms Underlying Eukaryotic Complexity

Eukaryotic ESCRT complexes remodel membranes at the plasma membrane and internal compartments, yet how these systems evolved from prokaryotic precursors functioning at the cellular membrane remains unresolved. Here, we show that ESCRT-II, ESCRT-III, VPS4, and ubiquitin from Candidatus Prometheoarchaeum syntrophicum (MK-D1), an Asgard archaeon closely related to eukaryotes, are recruited to canonical ESCRT sites in human cells, including centrosomes, midbodies, nuclear envelopes, endosomes despite the absence of these structures from MK-D1 morphology. In addition to MK-D1 ESCRT II recruitment at these regions, MK-D1 ESCRT-III and VPS4 form ring assemblies at midbodies and target reforming nuclear envelope regions. Futhermore, expression of MK-D1 ESCRT modules enhances efficiency of viral budding in human cells. These findings provide direct experimental evidence that archaeal ESCRT modules integrate into diverse eukaryotic structures, supporting a model in which ancestral membrane-remodeling systems were redeployed during eukaryogenesis to organize novel internal architectures.

evolutionary biology↗

bioRxiv2025

Ordering from the edge: Chiral multicellular pattern formation directed by actin self-organisation in cells

The mechanisms underlying both the establishment of mirror symmetry and deviations from it in development of bilateral multicellular organisms remain insufficiently understood. Actin cytoskeletons of individual cells exhibit intrinsic chirality, and a strong correlation exists between single-cell actin fibres chiral organisation and the collective alignment of cells confined to rectangular adhesive islands (2D-microtissues). Here, we demonstrate how multicellular chiral patterns can be inferred from the chiral behaviour of actin fibres in individual cells. By analysing chiral actin systems in cells with elliptical and semi-circular shapes, representing inner and boundary positions within 2D-microtissues, we defined the rules of chiral motile behaviour and formulated two models of cell alignment: (i) chiral rotation of inner cells and (ii) chiral tilting of boundary cells relative to island edges. In both models, neighbouring cells are also mutually aligned. Systematic variation of island area and aspect ratio, combined with dynamic observations, revealed the primary role of boundary cells. Chiral order first emerged at tissue boundaries and then propagated inward. This outside-in mechanism also explains why mirror-symmetric cell groups are difficult to achieve with uniformly chiral cells, but can be obtained either by reversing chirality in one subgroup or by enlarging the microtissue to minimise boundary influence.

biophysics↗

bioRxiv2023

Focal adhesions are controlled by microtubules through local contractility regulation

Microtubules regulate cell polarity and migration by local activation of focal adhesion turnover, but the mechanism of this process is insufficiently understood. Molecular complexes containing KANK family proteins connect microtubules with the major component of focal adhesions, talin. Local optogenetic activation of KANK1-mediated links which promoted microtubule targeting to individual focal adhesion resulting in its centripetal sliding and rapid disassembly. The sliding is preceded by a local increase of traction force due to accumulation of myosin-II and actin in the proximity of the focal adhesion. Knockdown of Rho activator GEF-H1 prevented development of traction force and abolished sliding and disassembly of focal adhesion upon KANK activation. Other players participating in microtubule-driven KANK-dependent focal adhesion disassembly include kinases ROCK and PAK, as well as microtubules/focal adhesions associated proteins Kinesin-1, APC and TAT. Finally, we propose a physical model of a microtubule-driven focal adhesion disruption involving local GEF-H1/RhoA/ROCK dependent activation of contractility which is consistent with experimental data.

cell biology↗

bioRxiv2022

Chiral growth of adherent filopodia

Adherent filopodia are elongated finger-like membrane protrusions, extending from the edges of diverse cell types and participating in cell adhesion, spreading, migration and environmental sensing. The formation and elongation of filopodia are driven by the polymerization of parallel actin filaments, comprising the filopodia cytoskeletal core. Here, we report that adherent filopodia, formed during the spreading of cultured cells on galectin-8-coated substrates, tend to change the direction of their extension in a chiral fashion, acquiring a left-bent shape. Cryo-electron tomography examination indicated that turning of the filopodia tip to the left is accompanied by the displacement of the actin core bundle to the right of the filopodia midline. Reduction of the adhesion to galectin-8 by treatment with thiodigalactoside abolished the filopodia chirality. By modulating the expression of a variety of actin-associated filopodia proteins, we identified myosin-X and formin DAAM1 as major filopodia chirality promoting factors. Formin mDia1, actin filament elongation factor VASP, and actin filament crosslinker fascin were also shown to be involved. Thus, the simple actin cytoskeleton of filopodia, together with a small number of associated proteins are sufficient to drive a complex navigation process, manifested by the development of left-right asymmetry in these cellular protrusions.

cell biology↗

bioRxiv2022

Semaphorin3F reduces vascular endothelial and smooth muscle cell PI3K activation and decreases neointimal plaque formation

We previously conducted genetic analyses, and identified semaphorin signaling as associating with coronary artery disease. Of the semaphorins, human vascular expression profiling suggested SEMA3F as potentially linked to atherogenesis. In hyperlipidemic mice, SEMA3F reduced aortic lesion area, and increased fibrous cap endothelial content, leading to plaque stability. In a disturbed-flow-mediated endothelial dysfunction-driven lesion model, the absence of Sema3f increased plaques, further implicating SEMA3F in endothelial function. Monocyte adhesion to Sema3f-/- vascular endothelial cells (VECs) was elevated, driven by increased PI3K activity, leading to increased NF-{kappa}B-mediated elevation in VCAM1 and ICAM1 expression, suggesting that SEMA3F reduces VEC PI3K activity. Increased permeability led to increased monocyte transmigration through Sema3f-/- VECs, and mTOR phosphorylation was decreased, suppressing VE-cadherin expression and cell-cell adherens junction stability. Actomyosin fiber formation was decreased in Sema3f-/- VECs, which was reversed by PI3K inhibition, further implicating SEMA3F in adherens junction stability. In Sema3f-/- vascular smooth muscle cells (VSMCs), active PI3K was also increased. PI3K facilitates VSMC proliferation, migration, and pro-atherogenic phenotype switching, which were reduced by SEMA3F. In agreement, in a model of VSMC proliferation and migration-induced neointima formation, SEMA3F reduced plaques. Semaphorin3F is causally atheroprotective. SEMA3Fs suppression of VEC and VSMC PI3K activation may contribute to its atheroprotection.

physiology↗

bioRxiv2020

Differential cellular responses to adhesive interactions with galectin-8 and fibronectin coated substrates

The mechanisms underlying the cellular response to extracellular matrices (ECM), consisting of multiple adhesive ligands, each with distinct properties, are still poorly understood. Here we address this topic by monitoring the cellular responses to two very different extracellular adhesion molecules - fibronectin and galectin-8 - and to mixtures of the two. Fibronectin is one of the major integrin ligands, inducing cell spreading and development of focal adhesions associated with contractile stress fibers. Galectin-8 is a mammalian lectin, which specifically binds to {beta}-galactoside residues present on some integrins, as well as to other cell surface receptors. We found marked differences in HeLa-JW cell spreading, assembly of focal adhesions and actomyosin stress fibers, and formation of adherent filopodia, on rigid flat substrates functionalized by fibronectin or galectin-8 alone, or by mixtures of these two proteins. Spreading on galectin-8 resulted in a larger projected cell area compared to that on fibronectin, by more extensive formation of filopodia, coupled with an inability to activate focal adhesion and stress fiber assembly. These differences could be partially reversed by experimental manipulations of small G-proteins of the Rho family and their downstream targets, such as formins, the Arp2/3 complex, and Rho kinase. Another factor affecting the spreading process was shown to be the enhanced physical adhesion of the cells to galectin-8, as compared to fibronectin. Notably, at least one process, the formation of adherent filopodia, was synergistically upregulated by both ligands, so filopodia development on the substrate coated with a mixture of fibronectin and galectin-8 was far more prominent than on each ligand alone.

cell biology↗

bioRxiv2018

Actin cytoskeleton self-organization in single epithelial cells and fibroblasts under isotropic confinement

We systematically investigated the principles of actin cytoskeleton self-organization in two cell types, fibroblasts and epitheliocytes, by confining isolated cells on isotropic adhesive islands of varying size. In fibroblasts, we previously described that an initially circular pattern of circumferential actin dynamically evolves into a radial pattern of actin bundles that spontaneously transforms into a chiral pattern, before finally producing parallel linear stress fibres. We now show that progression from circular to chiral actin patterns depends on cell projected area and rarely occurs on small islands. Epitheliocytes however, did not exhibit succession through all the actin patterns described above even on large islands. Upon confinement, the actin cytoskeleton in non-keratinocyte epitheliocytes is arrested at the circular stage, while in keratinocytes it can progress as far as the radial pattern but still cannot break symmetry. Epithelial-mesenchymal transition pushed actin cytoskeleton development from circular towards radial patterns but remains insufficient to cause chirality. Surprisingly, small doses of G-actin sequestering drug, latrunculin A, induced chiral swirling in keratinocytes. During this swirling, keratin filaments follow actin and also demonstrate chiral swirling movement. Elimination of the keratin network by genetic silencing of Type II keratins, however, did not affect the self-organization of the actin cytoskeleton.

cell biology↗