Local negative feedback of Rac activity at the leading edge underlies a pilot pseudopod-like program for amoeboid cell guidance.

To migrate efficiently, neutrophils must polarize their cytoskeletal regulators along a single axis of motion. This polarization process is thought to be mediated through local positive feedback that amplifies leading edge signals and global negative feedback that enables sites of positive feedback to compete for dominance. Though this two-component model efficiently establishes cell polarity, it has potential limitations, including a tendency to "lock" onto a particular direction, limiting the ability of cells to reorient.

Cell protrusions and contractions generate long-range membrane tension propagation.

Membrane tension is thought to be a long-range integrator of cell physiology. Membrane tension has been proposed to enable cell polarity during migration through front-back coordination and long-range protrusion competition. These roles necessitate effective tension transmission across the cell.

Mechanosensitive mTORC2 independently coordinates leading and trailing edge polarity programs during neutrophil migration.

By acting both upstream of and downstream from biochemical organizers of the cytoskeleton, physical forces function as central integrators of cell shape and movement. Here we use a combination of genetic, pharmacological, and optogenetic perturbations to probe the role of the conserved mechanosensitive mTOR complex 2 (mTORC2) programs in neutrophil polarity and motility. We find that the tension-based inhibition of leading-edge signals (Rac, F-actin) that underlies protrusion competition is gated by the kinase-independent role of the complex, whereas the regulation of RhoA and myosin II-based contractility at the trailing edge depend on mTORC2 kinase activity.

Progressive enhancement of kinetic proofreading in T cell antigen discrimination from receptor activation to DAG generation.

T cells use kinetic proofreading to discriminate antigens by converting small changes in antigen-binding lifetime into large differences in cell activation, but where in the signaling cascade this computation is performed is unknown. Previously, we developed a light-gated immune receptor to probe the role of ligand kinetics in T cell antigen signaling. We found significant kinetic proofreading at the level of the signaling lipid diacylglycerol (DAG) but lacked the ability to determine where the multiple signaling steps required for kinetic discrimination originate in the upstream signaling cascade (Tiseher and Weiner, 2019).

Carbon Dots for Carbon Dummies: The Quantum and The Molecular Questions Among Some Others.

Carbon Dots (CDs) are carbon nanoparticles which were discovered in 2004. Despite two decades of intensive work from the scientific community and a colossal amount of gathered experimental data, no definitive consensus exists to date on several key aspects such as the actual definition of CDs and the origin of their emissive properties. This review proposes a critical evaluation of these fundamental questions.

The WAVE complex associates with sites of saddle membrane curvature.

How local interactions of actin regulators yield large-scale organization of cell shape and movement is not well understood. Here we investigate how the WAVE complex organizes sheet-like lamellipodia. Using super-resolution microscopy, we find that the WAVE complex forms actin-independent 230-nm-wide rings that localize to regions of saddle membrane curvature.

Assembly of Genetic Circuits with the Mammalian ToolKit.

The ability to rapidly assemble and prototype cellular circuits is vital for biological research and its applications in biotechnology and medicine. The Mammalian ToolKit (MTK) is a Golden Gate-based cloning toolkit for fast, reproducible and versatile assembly of large DNA vectors and their implementation in mammalian models. The MTK consists of a curated library of characterized, modular parts that can be assembled into transcriptional units and further weaved into complex circuits.

A Toolkit for Rapid Modular Construction of Biological Circuits in Mammalian Cells.

The ability to rapidly assemble and prototype cellular circuits is vital for biological research and its applications in biotechnology and medicine. Current methods for the assembly of mammalian DNA circuits are laborious, slow, and expensive. Here we present the Mammalian ToolKit (MTK), a Golden Gate-based cloning toolkit for fast, reproducible, and versatile assembly of large DNA vectors and their implementation in mammalian models.

Cell confinement reveals a branched-actin independent circuit for neutrophil polarity.

Migratory cells use distinct motility modes to navigate different microenvironments, but it is unclear whether these modes rely on the same core set of polarity components. To investigate this, we disrupted actin-related protein 2/3 (Arp2/3) and the WASP-family verprolin homologous protein (WAVE) complex, which assemble branched actin networks that are essential for neutrophil polarity and motility in standard adherent conditions. Surprisingly, confinement rescues polarity and movement of neutrophils lacking these components, revealing a processive bleb-based protrusion program that is mechanistically distinct from the branched actin-based protrusion program but shares some of the same core components and underlying molecular logic.

Extending chemical perturbations of the ubiquitin fitness landscape in a classroom setting reveals new constraints on sequence tolerance.

Although the primary protein sequence of ubiquitin (Ub) is extremely stable over evolutionary time, it is highly tolerant to mutation during selection experiments performed in the laboratory. We have proposed that this discrepancy results from the difference between fitness under laboratory culture conditions and the selective pressures in changing environments over evolutionary timescales. Building on our previous work (Mavor et al.