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1. Magic angle spinning NMR structure of human cofilin-2 assembled on actin filaments reveals isoform-specific conformation and binding mode

   https://doi.org/10.1038/s41467-022-29595-9  

   Kraus, Jodi ; Russell, Ryan W. ; Kudryashova, Elena ; Xu, Chaoyi ; Katyal, Nidhi ; Perilla, Juan R. ; Kudryashov, Dmitri S. ; Polenova, Tatyana ( April 2022 , Nature Communications)

   Actin polymerization dynamics regulated by actin-binding proteins are essential for various cellular functions. The cofilin family of proteins are potent regulators of actin severing and filament disassembly. The structural basis for cofilin-isoform-specific severing activity is poorly understood as their high-resolution structures in complex with filamentous actin (F-actin) are lacking. Here, we present the atomic-resolution structure of the muscle-tissue-specific isoform, cofilin-2 (CFL2), assembled on ADP-F-actin, determined by magic-angle-spinning (MAS) NMR spectroscopy and data-guided molecular dynamics (MD) simulations. We observe an isoform-specific conformation for CFL2. This conformation is the result of a unique network of hydrogen bonding interactions within the α2 helix containing the non-conserved residue, Q26. Our results indicate F-site interactions that are specific between CFL2 and ADP-F-actin, revealing mechanistic insights into isoform-dependent F-actin disassembly.

    

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2. Multi-copper oxidases SKU5 and SKS1 coordinate cell wall formation using apoplastic redox-based reactions in roots

   https://doi.org/10.1093/plphys/kiad207  

   Chen, Chaofan ; Zhang, Yi ; Cai, Jianfa ; Qiu, Yuting ; Li, Lihong ; Gao, Chengxu ; Gao, Yiqun ; Ke, Meiyu ; Wu, Shengwei ; Wei, Chuan ; et al ( April 2023 , Plant Physiology)

   The primary cell wall is a fundamental plant constituent that is flexible but sufficiently rigid to support the plant cell shape. Although many studies have demonstrated that reactive oxygen species (ROS) serve as important signaling messengers to modify the cell wall structure and affect cellular growth, the regulatory mechanism underlying the spatial-temporal regulation of ROS activity for cell wall maintenance remains largely unclear. Here, we demonstrate the role of the Arabidopsis (Arabidopsis thaliana) multicopper oxidase-like protein skewed 5 (SKU5) and its homolog SKU5-similar 1 (SKS1) in root cell wall formation through modulating ROS homeostasis. Loss of SKU5 and SKS1 function resulted in aberrant division planes, protruding cell walls, ectopic deposition of iron, and reduced nicotinamide adeninedinucleotide phosphate (NADPH) oxidase-dependent ROS overproduction in the root epidermis–cortex and cortex–endodermis junctions. A decrease in ROS level or inhibition of NADPH oxidase activity rescued the cell wall defects of sku5 sks1 double mutants. SKU5 and SKS1 proteins were activated by iron treatment, and iron over-accumulated in the walls between the root epidermis and cortex cell layers of sku5 sks1. The glycosylphosphatidylinositol-anchored motif was crucial for membrane association and functionality of SKU5 and SKS1. Overall, our results identified SKU5 and SKS1 as regulators of ROS at the cell surface for regulation of cell wall structure and root cell growth.

    

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3. Spatiotemporal development of coexisting wave domains of Rho activity in the cell cortex

   https://doi.org/10.1038/s41598-021-99029-x  

   Hladyshau, Siarhei ; Kho, Mary ; Nie, Shuyi ; Tsygankov, Denis ( December 2021 , Scientific Reports)

   Abstract The Rho family GTPases are molecular switches that regulate cytoskeletal dynamics and cell movement through a complex spatiotemporal organization of their activity. In Patiria miniata (starfish) oocytes under in vitro experimental conditions (with overexpressed Ect2, induced expression of Δ90 cyclin B, and roscovitine treatment), such activity generates multiple co-existing regions of coherent propagation of actin waves. Here we use computational modeling to investigate the development and properties of such wave domains. The model reveals that the formation of wave domains requires a balance between the activation and inhibition in the Rho signaling motif. Intriguingly, the development of the wave domains is preceded by a stage of low-activity quasi-static patterns, which may not be readily observed in experiments. Spatiotemporal patterns of this stage and the different paths of their destabilization define the behavior of the system in the later high-activity (observable) stage. Accounting for a strong intrinsic noise allowed us to achieve good quantitative agreement between simulated dynamics in different parameter regimes of the model and different wave dynamics in Patiria miniata and wild type Xenopus laevis (frog) data. For quantitative comparison of simulated and experimental results, we developed an automated method of wave domain detection, which revealed a sharp reversal in the process of pattern formation in starfish oocytes. Overall, our findings provide an insight into spatiotemporal regulation of complex and diverse but still computationally reproducible cell-level actin dynamics. 

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4. The intimate and controversial relationship between voltage‐gated proton channels and the phagocyte NADPH oxidase

   https://doi.org/10.1111/imr.12437  

   DeCoursey, Thomas E. ( August 2016 , Immunological Reviews)

   One of the most fascinating and exciting periods in my scientific career entailed dissecting the symbiotic relationship between two membrane transporters, the Nicotinamide adenine dinucleotide phosphate reduced form (NADPH) oxidase complex and voltage‐gated proton channels (H_V1). By the time I entered this field, there had already been substantial progress toward understandingNADPHoxidase, but H_V1 were known only to a tiny handful of cognoscenti around the world. Having identified the first proton currents in mammalian cells in 1991, I needed to find a clear function for these molecules if the work was to become fundable. The then‐recent discoveries of Henderson, Chappell, and colleagues in 1987–1988 that led them to hypothesize interactions of both molecules during the respiratory burst of phagocytes provided an excellent opportunity. In a nutshell, both transporters function by moving electrical charge across the membrane:NADPHoxidase moves electrons and H_V1 moves protons. The consequences of electrogenicNADPHoxidase activity on both membrane potential and pH strongly self‐limit this enzyme. Fortunately, both consequences specifically activate H_V1, and H_V1 activity counteracts both consequences, a kind of yin–yang relationship. Notwithstanding a decade starting in 1995 when many believed the opposite, these are two separate molecules that function independently despite their being functionally interdependent in phagocytes. The relationship betweenNADPHoxidase and H_V1 has become a paradigm that somewhat surprisingly has now extended well beyond the phagocyteNADPHoxidase – an industrial strength producer of reactive oxygen species (ROS) – to myriad other cells that produce orders of magnitude lessROSfor signaling purposes. These cells with their sevenNADPHoxidase (NOX) isoforms provide a vast realm of mechanistic obscurity that will occupy future studies for years to come.

    

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5. Catalytic MXCeO2 for enzyme based electrochemical biosensors: Fabrication, characterization and application towards a wearable sweat biosensor

   https://doi.org/10.1016/j.bios.2023.115975  

   Khan, Reem ; Andreescu, Silvana ( March 2024 , Biosensors and Bioelectronics)

   Two-dimensional (2D) layered materials that integrate metallic conductivity, catalytic activity and the ability to stabilize biological receptors provide unique capabilities for designing electrochemical biosensors for large-scale detection and diagnostic applications. Herein, we report a multifunctional MXene-based 2D nanostructure decorated with enzyme mimetic cerium oxide nanoparticle (MXCeO2) as a novel platform and catalytic amplifier for electrochemical biosensors, specifically targeting the detection of oxidase enzyme substrates. We demonstrate enhanced catalytic efficiency of the MXCeO2 for the reduction of hydrogen peroxide (H2O2) and its ability to immobilize oxidase enzymes, such as glucose oxidase, lactate oxidase and xanthine oxidase. The designed biosensors exhibit high selectivity, stability, and sensitivity, achieving detection limits of 0.8 μM H2O2, 0.49 μM glucose, 3.6 μM lactate and 1.7 μM hypoxanthine, when the MXCeO2 and their respective enzymes were used. The MXCeO2 was successfully incorporated into a wearable fabric demonstrating high sensitivity for lactate measurements in sweat. The unique combination of MXenes with CeO2 offers excellent conductivity, catalytic efficiency and enhanced enzyme loading, demonstrating potential of the MXCeO2 as a catalytically active material to boost efficiency of oxidase enzyme reactions. This design can be used as a general platform for increasing the sensitivity of enzyme based biosensors and advance the development of electrochemical biosensors for a variety of applications. 

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