Small GTPases use GDP/GTP alternation to actuate a variety of functional switches that are pivotal for cell dynamics. The GTPase switch is turned on by GEFs, which stimulate dissociation of the tig...

Regulation of Small GTPases by GEFs, GAPs, and GDIs

Clathrin-mediated endocytosis is a key process in vesicular trafficking that transports a wide range of cargo molecules from the cell surface to the interior. Clathrin-mediated endocytosis was first described over 5 decades ago. Since its discovery, over 50 proteins have been shown to be part of the molecular machinery that generates the clathrin-coated endocytic vesicles. These proteins and the different steps of the endocytic process that they mediate have been studied in detail. However, we still lack a good understanding of how all these different components work together in a highly coordinated manner to drive vesicle formation. Nevertheless, studies in recent years have provided several important insights into how endocytic vesicles are built, starting from initiation, cargo loading and the mechanisms governing membrane bending to membrane scission and the release of the vesicle into the cytoplasm.

Mechanisms of clathrin-mediated endocytosis.

The spatial and temporal organization of molecules within a cell is critical for coordinating the many distinct activities carried out by the cell. In an increasing number of biological signaling processes, scaffold proteins have been found to play a central role in physically assembling the relevant molecular components. Although most scaffolds use a simple tethering mechanism to increase the efficiency of interaction between individual partner molecules, these proteins can also exert complex allosteric control over their partners and are themselves the target of regulation. Scaffold proteins offer a simple, flexible strategy for regulating selectivity in pathways, shaping output behaviors, and achieving new responses from preexisting signaling components. As a result, scaffold proteins have been exploited by evolution, pathogens, and cellular engineers to reshape cellular behavior.

/pdf/scaffold-proteins-hubs-for-controlling-the-flow-of-cellular-1f32b85dj2.pdf

Scaffold Proteins: Hubs for Controlling the Flow of Cellular Information

The interior of a living cell is a crowded, heterogenuous, fluctuating environment. Hence, a major challenge in modeling intracellular transport is to analyze stochastic processes within complex environments. Broadly speaking, there are two basic mechanisms for intracellular transport: passive diffusion and motor-driven active transport. Diffusive transport can be formulated in terms of the motion of an overdamped Brownian particle. On the other hand, active transport requires chemical energy, usually in the form of adenosine triphosphate hydrolysis, and can be direction specific, allowing biomolecules to be transported long distances; this is particularly important in neurons due to their complex geometry. In this review a wide range of analytical methods and models of intracellular transport is presented. In the case of diffusive transport, narrow escape problems, diffusion to a small target, confined and single-file diffusion, homogenization theory, and fractional diffusion are considered. In the case of active transport, Brownian ratchets, random walk models, exclusion processes, random intermittent search processes, quasi-steady-state reduction methods, and mean-field approximations are considered. Applications include receptor trafficking, axonal transport, membrane diffusion, nuclear transport, protein-DNA interactions, virus trafficking, and the self-organization of subcellular structures.

/pdf/stochastic-models-of-intracellular-transport-2i2ybq04cg.pdf

Stochastic models of intracellular transport

We developed a method to use any GFP-tagged construct in single-molecule super-resolution microscopy By targeting GFP with small, high-affinity antibodies coupled to organic dyes, we achieved nanometer spatial resolution and minimal linkage error when analyzing microtubules, living neurons and yeast cells We show that in combination with libraries encoding GFP-tagged proteins, virtually any known protein can immediately be used in super-resolution microscopy and that simplified labeling schemes allow high-throughput super-resolution imaging

A simple, versatile method for GFP-based super-resolution microscopy via nanobodies

Symmetry-Breaking Polarization Driven by a Cdc42p GEF-PAK Complex

https://www.cell.com/cell/pdf/S0092-8674(12)00342-X.pdf

Negative Feedback Enhances Robustness in the Yeast Polarity Establishment Circuit

https://goryachev.bio.ed.ac.uk/goryachev/sites/sbsweb2.bio.ed.ac.uk.goryachev/files/pdf/cell1109.pdf

Singularity in polarization: rewiring yeast cells to make two buds.

Studies of the processes leading to the construction of a bud and its separation from the mother cell in Saccharomyces cerevisiae have provided foundational paradigms for the mechanisms of polarity establishment, cytoskeletal organization, and cytokinesis. Here we review our current understanding of how these morphogenetic events occur and how they are controlled by the cell-cycle-regulatory cyclin-CDK system. In addition, defects in morphogenesis provide signals that feed back on the cyclin-CDK system, and we review what is known regarding regulation of cell-cycle progression in response to such defects, primarily acting through the kinase Swe1p. The bidirectional communication between morphogenesis and the cell cycle is crucial for successful proliferation, and its study has illuminated many elegant and often unexpected regulatory mechanisms. Despite considerable progress, however, many of the most puzzling mysteries in this field remain to be resolved.

https://www.genetics.org/content/genetics/190/1/51.full.pdf

Audrey S. Howell

Papers

Symmetry-Breaking Polarization Driven by a Cdc42p GEF-PAK Complex

Negative Feedback Enhances Robustness in the Yeast Polarity Establishment Circuit

Singularity in polarization: rewiring yeast cells to make two buds.

Morphogenesis and the Cell Cycle

Modeling vesicle traffic reveals unexpected consequences for Cdc42p-mediated polarity establishment.