Elizabeth Smythe

Bio: Elizabeth Smythe is an academic researcher from University of Sheffield. The author has contributed to research in topics: Endocytosis & Clathrin. The author has an hindex of 27, co-authored 44 publications receiving 4989 citations. Previous affiliations of Elizabeth Smythe include University College London & University of Dundee.

Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity

Abstract: Inspired by the insect-eating Nepenthes pitcher plant, which snares its prey on a surface lubricated by a remarkably slippery aqueous secretion, Joanna Aizenberg and colleagues have synthesized omniphobic surfaces that can self-repair and function at high pressures. Their 'slippery liquid-infused porous surfaces' (or SLIPS) exhibit almost perfect slipperiness towards polar, organic and complex liquids. SLIPS function under extreme conditions, are easily constructed from inexpensive materials and can be endowed with other useful characteristics, such as enhanced optical transparency, through the selection of appropriate substrates and lubricants. Ultra-slippery surfaces of this type might find application in biomedical fluid handling, fuel transport, antifouling, anti-icing, optical imaging and elsewhere. Creating a robust synthetic surface that repels various liquids would have broad technological implications for areas ranging from biomedical devices and fuel transport to architecture but has proved extremely challenging1. Inspirations from natural nonwetting structures2,3,4,5,6, particularly the leaves of the lotus, have led to the development of liquid-repellent microtextured surfaces that rely on the formation of a stable air–liquid interface7,8,9. Despite over a decade of intense research, these surfaces are, however, still plagued with problems that restrict their practical applications: limited oleophobicity with high contact angle hysteresis9, failure under pressure10,11,12 and upon physical damage1,7,11, inability to self-heal and high production cost1,11. To address these challenges, here we report a strategy to create self-healing, slippery liquid-infused porous surface(s) (SLIPS) with exceptional liquid- and ice-repellency, pressure stability and enhanced optical transparency. Our approach—inspired by Nepenthes pitcher plants13—is conceptually different from the lotus effect, because we use nano/microstructured substrates to lock in place the infused lubricating fluid. We define the requirements for which the lubricant forms a stable, defect-free and inert ‘slippery’ interface. This surface outperforms its natural counterparts2,3,4,5,6 and state-of-the-art synthetic liquid-repellent surfaces8,9,14,15,16 in its capability to repel various simple and complex liquids (water, hydrocarbons, crude oil and blood), maintain low contact angle hysteresis (<2.5°), quickly restore liquid-repellency after physical damage (within 0.1–1 s), resist ice adhesion, and function at high pressures (up to about 680 atm). We show that these properties are insensitive to the precise geometry of the underlying substrate, making our approach applicable to various inexpensive, low-surface-energy structured materials (such as porous Teflon membrane). We envision that these slippery surfaces will be useful in fluid handling and transportation, optical sensing, medicine, and as self-cleaning and anti-fouling materials operating in extreme environments.

A novel role for Rab5-GDI in ligand sequestration into clathrin-coated pits

Abstract: BACKGROUND: Clathrin-coated pits are formed at the plasma membrane by the assembly of the coat components, namely clathrin and adaptors from the cytosol. Little is known about the regulation and mechanism of this assembly process. RESULTS: We have used an in vitro assay for clathrin-coated pit assembly to identify a novel component required for the invagination of newly formed coated pits. We have purified this cytosolic component and shown it to be a complex of Rab5 and GDI (guanine-nucleotide dissociation inhibitor), that was previously demonstrated to be involved in downstream processing of endocytic vesicles. Using a combination of quantitative electron microscopy and in vitro endocytosis assays, we have demonstrated that although coat proteins and ATP are sufficient to increase the number of new coated pits at the cell surface in permeabilised cells, the Rab5-GDI complex is required for ligand sequestration into clathrin-coated pits. CONCLUSIONS: We have identified Rab5 as a critical cytosolic component required for clathrin-coated pit function. Given the well-established role of Rab5 in the fusion of endocytic vesicles with endosomes, our results suggest that recruitment of essential components of the targeting and fusion machinery is coupled to the formation of functional transport vesicles.

Actin regulation in endocytosis.

Abstract: Increasing evidence from a variety of cell types has highlighted the importance of the actin cytoskeleton during endocytosis. No longer is actin viewed as a passive barrier that must be removed to allow endocytosis to proceed. Rather, actin structures are dynamically organised to assist the remodelling of the cell surface to allow inward movement of vesicles. The majority of our mechanistic insight into the role of actin in endocytosis has come from studies in budding yeast. Although endocytosis in mammalian cells is clearly more complex and subject to a greater array of regulatory signals, recent advances have revealed actin, and actin-regulatory proteins, to be present at endocytic sites. Furthermore, live cell imaging indicates that spatiotemporal aspects of actin recruitment and vesicle formation are likely to be conserved across eukaryotic evolution.

The mechanism of receptor-mediated endocytosis

Abstract: Receptor-mediated endocytosis is a mechanism used by cells for the uptake of macromolecules from the extracellular fluid It is a process found in all eukaryotic organisms in the plant and animal kingdoms The early work of Roth and Porter (1964), which showed the uptake of yolk proteins into mosquito oocytes, first indicated that cells are capable of the selective internalisation of molecules from the extracellular environment and that this process occurred via specialised regions of the plasma membrane, termed coated pits Later studies on the internalisation of low-density lipoprotein (LDL) outlined some of the early events on the pathway (Anderson et al, 1977) and these are shown schematically in Fig 1 Ligands bind to specific membrane-spanning receptors located on the cell surface and the receptor/ligand complexes become clustered into coated pits Included among the molecules taken up by receptor-mediated endocytosis are nutrients (LDL and transferrin), growth factors (epidermal growth factor), hormones (insulin), certain viruses and other foreign antigens

Quantum Dot Bioconjugates for Ultrasensitive Nonisotopic Detection

Abstract: Highly luminescent semiconductor quantum dots (zinc sulfide-capped cadmium selenide) have been covalently coupled to biomolecules for use in ultrasensitive biological detection. In comparison with organic dyes such as rhodamine, this class of luminescent labels is 20 times as bright, 100 times as stable against photobleaching, and one-third as wide in spectral linewidth. These nanometer-sized conjugates are water-soluble and biocompatible. Quantum dots that were labeled with the protein transferrin underwent receptor-mediated endocytosis in cultured HeLa cells, and those dots that were labeled with immunomolecules recognized specific antibodies or antigens.

Regulated portals of entry into the cell

Abstract: The plasma membrane is the interface between cells and their harsh environment. Uptake of nutrients and all communication among cells and between cells and their environment occurs through this interface. 'Endocytosis' encompasses several diverse mechanisms by which cells internalize macromolecules and particles into transport vesicles derived from the plasma membrane. It controls entry into the cell and has a crucial role in development, the immune response, neurotransmission, intercellular communication, signal transduction, and cellular and organismal homeostasis. As the complexity of molecular interactions governing endocytosis are revealed, it has become increasingly clear that it is tightly coordinated and coupled with overall cell physiology and thus, must be viewed in a broader context than simple vesicular trafficking.

Rab proteins as membrane organizers

Abstract: Cellular organelles in the exocytic and endocytic pathways have a distinctive spatial distribution and communicate through an elaborate system of vesiculo-tubular transport. Rab proteins and their effectors coordinate consecutive stages of transport, such as vesicle formation, vesicle and organelle motility, and tethering of vesicles to their target compartment. These molecules are highly compartmentalized in organelle membranes, making them excellent candidates for determining transport specificity and organelle identity.

Rab GTPases as coordinators of vesicle traffic.

Abstract: Rab GTPases control intracellular vesicle traffic by acting as regulatable switches that recruit effector molecules when in their GTP-bound form. The functional coupling between multiple Rab GTPases ensures the spatiotemporally coordinated regulation of vesicle traffic. Membrane trafficking between organelles by vesiculotubular carriers is fundamental to the existence of eukaryotic cells. Central in ensuring that cargoes are delivered to their correct destinations are the Rab GTPases, a large family of small GTPases that control membrane identity and vesicle budding, uncoating, motility and fusion through the recruitment of effector proteins, such as sorting adaptors, tethering factors, kinases, phosphatases and motors. Crosstalk between multiple Rab GTPases through shared effectors, or through effectors that recruit selective Rab activators, ensures the spatiotemporal regulation of vesicle traffic. Functional impairments of Rab pathways are associated with diseases, such as immunodeficiencies, cancer and neurological disorders.

Small GTP-Binding Proteins

Abstract: Small GTP-binding proteins (G proteins) exist in eukaryotes from yeast to human and constitute a superfamily consisting of more than 100 members. This superfamily is structurally classified into at least five families: the Ras, Rho, Rab, Sar1/Arf, and Ran families. They regulate a wide variety of cell functions as biological timers (biotimers) that initiate and terminate specific cell functions and determine the periods of time for the continuation of the specific cell functions. They furthermore play key roles in not only temporal but also spatial determination of specific cell functions. The Ras family regulates gene expression, the Rho family regulates cytoskeletal reorganization and gene expression, the Rab and Sar1/Arf families regulate vesicle trafficking, and the Ran family regulates nucleocytoplasmic transport and microtubule organization. Many upstream regulators and downstream effectors of small G proteins have been isolated, and their modes of activation and action have gradually been elucidated. Cascades and cross-talks of small G proteins have also been clarified. In this review, functions of small G proteins and their modes of activation and action are described.