Biology subjects

Byfield, F. J.

Publications and source records attributed to Byfield, F. J..

4 recordsLinked to original sources

bioRxiv2025

Role of nuclear ATPases in nuclear mechanics and cell migration through confined spaces: opposite effects of BRG1 and cohesin

Deformation of the nucleus often presents a barrier to cell migration through tight spaces, such as those encountered as cells move through tissues or across extracellular matrix barriers. Reorganization of the nucleus to allow its passage through spaces much smaller than its resting diameter requires forces generated by the cytoskeleton, as well as active reorganization within the nucleus driven by ATPases that crosslink or move chromatin. Here, we show that two different nuclear ATPases, the BRG1/SMARCA4 motor of the BAF or SWI/SNF complex and the bifunctional crosslinking and loop extruding complex, cohesin, have opposite effects on the stiffness of isolated nuclei. Inhibition of BRG1 stiffens the nucleus, and cohesin softens it in karyoplasts derived from multiple cell types, including four different cancer cells, fibroblasts, and mesenchymal stem cells. The effects on isolated nuclear stiffness coincide with the effects of these ATPases on the ability of cells to migrate through tight spaces. Stiffening the nucleus inhibits single cell migration through micron-sized pores and the outward migration of tumor cell spheroids into a surrounding collagen matrix. Softening the nucleus by inhibiting cohesin has the opposite effect: it enhances single-cell migration through pores, at least for some cell types, and facilitates the outgrowth of cells from a tumor cell spheroid into the surrounding matrix. These results emphasize the importance of active motions generated within the nucleus for the global mechanics of the nucleus and the way that it deforms in response to externally generated stresses. Statement of significanceCells often move through tight spaces within three-dimensional materials. This constricted motion requires deformation of the nucleus, which is often stiffer and less dynamic than the rest of the cell. Nuclear deformation is achieved in part by forces generated outside the nucleus, primarily by cytoskeletal motors, but nuclear deformation is also affected by intranuclear motor proteins that move and reorganize chromatin. Here we show that the activity of DNA binding chromatin remodeling ATPases affects not only the stiffness of the isolated nucleus but also the ability of cells to deform as they move through tight spaces. Inhibition of motors such as BRG1 that fluidize the nucleus prevents cell movement through tight spaces, whereas inactivation of the crosslinking ATPase cohesin tends to enhance it.

biophysics↗

bioRxiv2024

Vimentin molecular linkages with nesprin-3 enhance nuclear deformation by cell geometric constraints

The nucleus is the organelle of the cell responsible for controlling protein expression, which has a direct effect on cellular biological functions. Here we show that the cytoskeletal protein vimentin plays an important role in increasing cell-generated forces transmitted to the cell nucleus, resulting in increased nuclear deformations in strongly polarized cells. Using micropatterned substrates to geometrically control cell shape in wild-type and vimentin-null cells, we show vimentin increases polarization and deformation of the cell nucleus. Loss of nesprin-3, which physically couples vimentin to the nuclear envelope, phenotypically copies the loss of vimentin, suggesting vimentin transmits forces to the cell nucleus through direct molecular linkages. Use of a fluorescence resonance energy transfer (FRET) sensor that binds to the nuclear envelope through lamin-A/C suggests vimentin increases the tension on the nuclear envelope. Our results indicate that nuclear shape and deformation can be modified by the vimentin cytoskeleton and its specific crosslinks to the cell nucleus.

biophysics↗

bioRxiv2022

Extracellular vimentin is sufficient to promote cell attachment, spreading, and motility by a mechanism involving N-acetyl glucosamine-containing structures

Vimentin intermediate filaments form part of the cytoskeleton of mesenchymal cells, but under pathological conditions often associated with inflammation, vimentin filaments depolymerize as the result of phosphorylation or citrullination, and vimentin oligomers are secreted or released into the extracellular environment. In the extracellular space, vimentin can bind surfaces of other cells and the extracellular matrix, and the interaction between extracellular vimentin and other cell types can trigger changes in cellular functions, such as activation of fibroblasts to a fibrotic phenotype. The mechanism by which extracellular vimentin binds external cell membranes and whether vimentin alone can act as an adhesive anchor for cells is largely uncharacterized. Here, we show that various cell types (normal and vimentin null fibroblasts, mesenchymal stem cells, A549 lung carcinoma cells) attach to and spread on polyacrylamide hydrogel substrates covalently linked to vimentin. Using traction force microscopy and spheroid expansion assays, we characterize how different cell types respond to extracellular vimentin. Cell attachment to and spreading on vimentin-coated surfaces is inhibited by hyaluronic acid (HA) degrading enzymes, HA synthase inhibitors, soluble heparin, or N-acetyl glucosamine, treatments that have little or no effect on the same cell types binding to collagen-coated hydrogels. These studies highlight the effectiveness of substrate-bound vimentin as a ligand for cells and suggest that carbohydrate structures, including the glycocalyx and glycosylated cell surface proteins that contain N-acetyl glucosamine, form a novel class of adhesion receptors for extracellular vimentin.

biophysics↗

bioRxiv2018

Loss of vimentin intermediate filaments decreases peri-nuclear stiffness and enhances cell motility through confined spaces

The migration of cells through tight constricting spaces or along fibrous tracks in tissues is important for biological processes, such as embryogenesis, wound healing, and cancer metastasis, and depends on the mechanical properties of the cytoskeleton. Migratory cells often express and upregulate the intermediate filament protein vimentin. The viscoelasticity of vimentin networks in shear deformation has been documented, but its role in motility is largely unexplored. Here, we studied the effects of vimentin on cell motility and stiffness using mouse embryo fibroblasts derived from wild-type and vimentin-null mice. We find that loss of vimentin increases motility through small pores and along thin capillaries. Atomic force microscopy measurements reveal that the presence of vimentin enhances the perinuclear stiffness of the cell, to an extent that depends on surface ligand presentation and therefore signaling from extracellular matrix receptors. Together, our results indicate that vimentin hinders three-dimensional motility by providing mechanical resistance against large strains and may thereby protect the structural integrity of cells.

biophysics↗