Coaching ribosome biogenesis from the nuclear periphery.

Severe invagination of the nuclear envelope is a hallmark of cancers, aging, neurodegeneration, and infections. However, the outcomes of nuclear invagination remain unclear. This work identified a new function of nuclear invagination: regulating ribosome biogenesis. With expansion microscopy, we observed frequent physical contact between nuclear invaginations and nucleoli. Surprisingly, the higher the invagination curvature, the more ribosomal RNA and pre-ribosomes are made in the contacted nucleolus. By growing cells on nanopillars that generate nuclear invaginations with desired curvatures, we can increase and decrease ribosome biogenesis. Based on this causation, we repressed the ribosome levels in breast cancer and progeria cells by growing cells on low-curvature nanopillars, indicating that overactivated ribosome biogenesis can be rescued by reshaping nuclei. Mechanistically, high-curvature nuclear invaginations reduce heterochromatin and enrich nuclear pore complexes, which promote ribosome biogenesis. We anticipate that our findings will serve as a foundation for further studies on nuclear deformation.

Membrane curvature catalyzes actin nucleation through nano-scale condensation of N-WASP-FBP17.

Actin remodeling is spatiotemporally regulated by surface topographical cues on the membrane for signaling across diverse biological processes. Yet, the mechanism dynamic membrane curvature prompts quick actin cytoskeletal changes in signaling remain elusive. Leveraging the precision of nanolithography to control membrane curvature, we reconstructed catalytic reactions from the detection of nano-scale curvature by sensing molecules to the initiation of actin polymerization, which is challenging to study quantitatively in living cells. We show that this process occurs via topographical signal-triggered condensation and activation of the actin nucleation-promoting factor (NPF), Neuronal Wiskott-Aldrich Syndrome protein (N-WASP), which is orchestrated by curvature-sensing BAR-domain protein FBP17. Such N-WASP activation is fine-tuned by optimizing FBP17 to N-WASP stoichiometry over different curvature radii, allowing a curvature-guided macromolecular assembly pattern for polymerizing actin network locally. Our findings shed light on the intricate relationship between changes in curvature and actin remodeling via spatiotemporal regulation of NPF/BAR complex condensation.

Two-dimensional molecular condensation in cell signaling and mechanosensing.

Membraneless organelles (MLO) regulate diverse biological processes in a spatiotemporally controlled manner spanning from inside to outside of the cells. The plasma membrane (PM) at the cell surface serves as a central platform for forming multi-component signaling hubs that sense mechanical and chemical cues during physiological and pathological conditions. During signal transduction, the assembly and formation of membrane-bound MLO are dynamically tunable depending on the physicochemical properties of the surrounding environment and partitioning biomolecules. Biomechanical properties of MLO-associated membrane structures can control the microenvironment for biomolecular interactions and assembly. Lipid-protein complex interactions determine the catalytic region's assembly pattern and assembly rate and, thereby, the amplitude of activities. In this review, we will focus on how cell surface microenvironments, including membrane curvature, surface topology and tension, lipid-phase separation, and adhesion force, guide the assembly of PM-associated MLO for cell signal transductions.

Biomolecular condensates tunes immune signaling at the Host-Pathogen interface.

Membraneless organelles participate in diverse spatiotemporal regulation of cellular signal transduction by recruiting necessary signaling factors. During host-pathogen interactions, the plasma membrane (PM) at the interface between the plant and microbes serves as a central platform for forming multicomponent immune signaling hubs. The macromolecular condensation of the immune complex and regulators is important in regulating immune signaling outputs regarding strength, timing, and crosstalk between signaling pathways. This review discusses mechanisms that regulate specific and crosstalk of plant immune signal transduction pathways through macromolecular assembly and condensation.

Membrane curvature governs the distribution of Piezo1 in live cells.

Piezo1 is a bona fide mechanosensitive ion channel ubiquitously expressed in mammalian cells. The distribution of Piezo1 within a cell is essential for various biological processes including cytokinesis, cell migration, and wound healing. However, the underlying principles that guide the subcellular distribution of Piezo1 remain largely unexplored. Here, we demonstrate that membrane curvature serves as a key regulator of the spatial distribution of Piezo1 in the plasma membrane of living cells. Piezo1 depletes from highly curved membrane protrusions such as filopodia and enriches to nanoscale membrane invaginations. Quantification of the curvature-dependent sorting of Piezo1 directly reveals the in situ nano-geometry of the Piezo1-membrane complex. Piezo1 density on filopodia increases upon activation, independent of calcium, suggesting flattening of the channel upon opening. Consequently, the expression of Piezo1 inhibits filopodia formation, an effect that diminishes with channel activation.

Guiding Irregular Nuclear Morphology on Nanopillar Arrays for Malignancy Differentiation in Tumor Cells.

For more than a century, abnormal nuclei in tumor cells, presenting subnuclear invaginations and folds on the nuclear envelope, have been known to be associated with high malignancy and poor prognosis. However, current nuclear morphology analysis focuses on the features of the entire nucleus, overlooking the malignancy-related subnuclear features in nanometer scale. The main technical challenge is to probe such tiny and randomly distributed features inside cells. We here employ nanopillar arrays to guide subnuclear features into ordered patterns, enabling their quantification as a strong indicator of cell malignancy. Both breast and liver cancer cells were validated as well as the quantification of nuclear abnormality heterogeneity. The alterations of subnuclear patterns were also explored as effective readouts for drug treatment. We envision that this nanopillar-enabled quantification of subnuclear abnormal features in tumor cells opens a new angle in characterizing malignant cells and studying the unique nuclear biology in cancer.

Dual-targeting nanovesicles enhance specificity to dynamic tumor cells in vitro and in vivo via manipulation of αvß3-ligand binding.

The dynamic or flowing tumor cells just as leukemia cells and circulating tumor cells face a microenvironment difference from the solid tumors, and the related targeting nanomedicines are rarely reported. The existence of fluidic shear stress in blood circulation seems not favorable for the binding of ligand modified nanodrugs with their target receptor. Namely, the binding feature is very essential in this case. Herein, we utilized HSPC, PEG-DSPE, cholesterol and two αvß3 ligands (RGDm7 and DT4) with different binding rates to build dual-targeting nanovesicles, in an effort to achieve a "fast-binding/slow-unbinding" function. It was demonstrated that the dual-targeting nanovesicles actualized efficient cellular uptake and antitumor effect in vitro both for static and dynamic tumor cells. Besides, the potency of the dual-targeting vesicles for flowing tumor cells was better than that for static tumor cells. Then, a tumor metastasis mice model and a leukemia mice model were established to detect the killing ability of the drug-loaded dual-targeting vesicles to dynamic tumor cells in vivo. The therapy efficacy of the dual-targeting system was higher than other controls including single-targeting ones. Generally, it seems possible to strengthen drug-targeting to dynamic tumor cells via the control of ligand-receptor interaction.