TY - JOUR AB - Cell and tissue polarization is fundamental for plant growth and morphogenesis. The polar, cellular localization of Arabidopsis PIN‐FORMED (PIN) proteins is crucial for their function in directional auxin transport. The clustering of PIN polar cargoes within the plasma membrane has been proposed to be important for the maintenance of their polar distribution. However, the more detailed features of PIN clusters and the cellular requirements of cargo clustering remain unclear. Here, we characterized PIN clusters in detail by means of multiple advanced microscopy and quantification methods, such as 3D quantitative imaging or freeze‐fracture replica labeling. The size and aggregation types of PIN clusters were determined by electron microscopy at the nanometer level at different polar domains and at different developmental stages, revealing a strong preference for clustering at the polar domains. Pharmacological and genetic studies revealed that PIN clusters depend on phosphoinositol pathways, cytoskeletal structures and specific cell‐wall components as well as connections between the cell wall and the plasma membrane. This study identifies the role of different cellular processes and structures in polar cargo clustering and provides initial mechanistic insight into the maintenance of polarity in plants and other systems. AU - Li, Hongjiang AU - von Wangenheim, Daniel AU - Zhang, Xixi AU - Tan, Shutang AU - Darwish-Miranda, Nasser AU - Naramoto, Satoshi AU - Wabnik, Krzysztof T AU - de Rycke, Riet AU - Kaufmann, Walter AU - Gütl, Daniel J AU - Tejos, Ricardo AU - Grones, Peter AU - Ke, Meiyu AU - Chen, Xu AU - Dettmer, Jan AU - Friml, Jiří ID - 8582 IS - 1 JF - New Phytologist SN - 0028646X TI - Cellular requirements for PIN polar cargo clustering in Arabidopsis thaliana VL - 229 ER - TY - JOUR AB - The recent outbreak of coronavirus disease 2019 (COVID‐19), caused by the Severe Acute Respiratory Syndrome Coronavirus‐2 (SARS‐CoV‐2) has resulted in a world‐wide pandemic. Disseminated lung injury with the development of acute respiratory distress syndrome (ARDS) is the main cause of mortality in COVID‐19. Although liver failure does not seem to occur in the absence of pre‐existing liver disease, hepatic involvement in COVID‐19 may correlate with overall disease severity and serve as a prognostic factor for the development of ARDS. The spectrum of liver injury in COVID‐19 may range from direct infection by SARS‐CoV‐2, indirect involvement by systemic inflammation, hypoxic changes, iatrogenic causes such as drugs and ventilation to exacerbation of underlying liver disease. This concise review discusses the potential pathophysiological mechanisms for SARS‐CoV‐2 hepatic tropism as well as acute and possibly long‐term liver injury in COVID‐19. AU - Nardo, Alexander D. AU - Schneeweiss-Gleixner, Mathias AU - Bakail, May M AU - Dixon, Emmanuel D. AU - Lax, Sigurd F. AU - Trauner, Michael ID - 8927 IS - 1 JF - Liver International SN - 14783223 TI - Pathophysiological mechanisms of liver injury in COVID-19 VL - 41 ER - TY - JOUR AB - Layered materials in which individual atomic layers are bonded by weak van der Waals forces (vdW materials) constitute one of the most prominent platforms for materials research. Particularly, polar vdW crystals, such as hexagonal boron nitride (h-BN), alpha-molybdenum trioxide (α-MoO3) or alpha-vanadium pentoxide (α-V2O5), have received significant attention in nano-optics, since they support phonon polaritons (PhPs)―light coupled to lattice vibrations― with strong electromagnetic confinement and low optical losses. Recently, correlative far- and near-field studies of α-MoO3 have been demonstrated as an effective strategy to accurately extract the permittivity of this material. Here, we use this accurately characterized and low-loss polaritonic material to sense its local dielectric environment, namely silica (SiO2), one of the most widespread substrates in nanotechnology. By studying the propagation of PhPs on α-MoO3 flakes with different thicknesses laying on SiO2 substrates via near-field microscopy (s-SNOM), we extract locally the infrared permittivity of SiO2. Our work reveals PhPs nanoimaging as a versatile method for the quantitative characterization of the local optical properties of dielectric substrates, crucial for understanding and predicting the response of nanomaterials and for the future scalability of integrated nanophotonic devices. AU - Aguilar-Merino, Patricia AU - Álvarez-Pérez, Gonzalo AU - Taboada-Gutiérrez, Javier AU - Duan, Jiahua AU - Prieto Gonzalez, Ivan AU - Álvarez-Prado, Luis Manuel AU - Nikitin, Alexey Y. AU - Martín-Sánchez, Javier AU - Alonso-González, Pablo ID - 9038 IS - 1 JF - Nanomaterials TI - Extracting the infrared permittivity of SiO2 substrates locally by near-field imaging of phonon polaritons in a van der Waals crystal VL - 11 ER - TY - JOUR AB - Sequence-specific oligomers with predictable folding patterns, i.e., foldamers, provide new opportunities to mimic α-helical peptides and design inhibitors of protein-protein interactions. One major hurdle of this strategy is to retain the correct orientation of key side chains involved in protein surface recognition. Here, we show that the structural plasticity of a foldamer backbone may notably contribute to the required spatial adjustment for optimal interaction with the protein surface. By using oligoureas as α helix mimics, we designed a foldamer/peptide hybrid inhibitor of histone chaperone ASF1, a key regulator of chromatin dynamics. The crystal structure of its complex with ASF1 reveals a notable plasticity of the urea backbone, which adapts to the ASF1 surface to maintain the same binding interface. One additional benefit of generating ASF1 ligands with nonpeptide oligourea segments is the resistance to proteolysis in human plasma, which was highly improved compared to the cognate α-helical peptide. AU - Mbianda, Johanne AU - Bakail, May M AU - André, Christophe AU - Moal, Gwenaëlle AU - Perrin, Marie E. AU - Pinna, Guillaume AU - Guerois, Raphaël AU - Becher, Francois AU - Legrand, Pierre AU - Traoré, Seydou AU - Douat, Céline AU - Guichard, Gilles AU - Ochsenbein, Françoise ID - 9262 IS - 12 JF - Science Advances SN - 2375-2548 TI - Optimal anchoring of a foldamer inhibitor of ASF1 histone chaperone through backbone plasticity VL - 7 ER - TY - JOUR AB - Gradients of chemokines and growth factors guide migrating cells and morphogenetic processes. Migration of antigen-presenting dendritic cells from the interstitium into the lymphatic system is dependent on chemokine CCL21, which is secreted by endothelial cells of the lymphatic capillary, binds heparan sulfates and forms gradients decaying into the interstitium. Despite the importance of CCL21 gradients, and chemokine gradients in general, the mechanisms of gradient formation are unclear. Studies on fibroblast growth factors have shown that limited diffusion is crucial for gradient formation. Here, we used the mouse dermis as a model tissue to address the necessity of CCL21 anchoring to lymphatic capillary heparan sulfates in the formation of interstitial CCL21 gradients. Surprisingly, the absence of lymphatic endothelial heparan sulfates resulted only in a modest decrease of CCL21 levels at the lymphatic capillaries and did neither affect interstitial CCL21 gradient shape nor dendritic cell migration toward lymphatic capillaries. Thus, heparan sulfates at the level of the lymphatic endothelium are dispensable for the formation of a functional CCL21 gradient. AU - Vaahtomeri, Kari AU - Moussion, Christine AU - Hauschild, Robert AU - Sixt, Michael K ID - 9259 JF - Frontiers in Immunology TI - Shape and function of interstitial chemokine CCL21 gradients are independent of heparan sulfates produced by lymphatic endothelium VL - 12 ER -