ALBERT

Beschreibung: 〈p〉Publication date: Available online 5 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Biophysical Journal〈/p〉 〈p〉Author(s): Thomas M. Kennelly, Yiran Li, Yi Cao, Eva E. Qwarnstrom, Mark Geoghegan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Dynamic single-molecule force spectroscopy was performed to monitor the unbinding of fibronectin with the proteoglycans syndecan-4 (SDC4) and decorin and to compare this with the unbinding characteristics of 〈em〉α〈/em〉〈sub〉5〈/sub〉〈em〉β〈/em〉〈sub〉1〈/sub〉-integrin. A single energy barrier was sufficient to describe the unbinding of both SDC4 and decorin from fibronectin, whereas two barriers were observed for the dissociation of 〈em〉α〈/em〉〈sub〉5〈/sub〉〈em〉β〈/em〉〈sub〉1〈/sub〉-integrin from fibronectin. The outer (high-affinity) barriers in the interactions of fibronectin with 〈em〉α〈/em〉〈sub〉5〈/sub〉〈em〉β〈/em〉〈sub〉1〈/sub〉-integrin and SDC4 are characterized by larger barrier heights and widths and slower dissociation rates than those of the inner (low-affinity) barriers in the interactions of fibronectin with 〈em〉α〈/em〉〈sub〉5〈/sub〉〈em〉β〈/em〉〈sub〉1〈/sub〉-integrin and decorin. These results indicate that SDC4 and (ultimately) 〈em〉α〈/em〉〈sub〉5〈/sub〉〈em〉β〈/em〉〈sub〉1〈/sub〉-integrin have the ability to withstand deformation in their interactions with fibronectin, whereas the decorin-fibronectin interaction is considerably more brittle.〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 3 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Biophysical Journal〈/p〉 〈p〉Author(s): Sabine Oldemeyer, Maria Mittag, Tilman Kottke〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cryptochromes function as flavin-binding photoreceptors in bacteria, fungi, algae, land plants, and insects. The discovery of an animal-like cryptochrome in the green alga 〈em〉Chlamydomonas reinhardtii〈/em〉 has expanded the spectral range of sensitivity of these receptors from ultraviolet A/blue light to almost the complete visible spectrum. The broadened light response has been explained by the presence of the flavin neutral radical as a chromophore in the dark. Concomitant with photoconversion of the flavin, an unusually long-lived tyrosyl radical with a red-shifted ultraviolet-visible spectrum is formed, which is essential for the function of the receptor. In this study, the microenvironment of this key residue, tyrosine 373, was scrutinized using time-resolved Fourier transform infrared spectroscopy on several variants of animal-like cryptochrome and density functional theory for band assignment. The reduced tyrosine takes on distinct hydrogen bond scenarios depending on the presence of the C-terminal extension and of a neighboring cysteine. Upon radical formation, all variants showed a signal at 1400 cm〈sup〉−1〈/sup〉, which we assigned to the 〈em〉ν〈/em〉7′a marker band of the CO stretching mode. The exceptionally strong downshift of this band cannot be attributed to a loss of hydrogen bonding only. Time-resolved ultraviolet-visible spectroscopy on W322F, a mutant of the neighboring tryptophan residue, revealed a decrease of the tyrosyl radical lifetime by almost two orders of magnitude, along with a shift of the absorbance maximum from 416 to 398 nm. These findings strongly support the concept of a 〈em〉π〈/em〉-〈em〉π〈/em〉 stacking as an apolar interaction between Y373 and W322 to be responsible for the characteristics of the tyrosyl radical. This concept of radical stabilization has been unknown to cryptochromes so far but might be highly relevant for other homologs with a tetrad of tryptophans and tyrosines as electron donors.〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Biophysical Journal〈/p〉 〈p〉Author(s): Sebastian Hillringhaus, Anil K. Dasanna, Gerhard Gompper, Dmitry A. Fedosov〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Invasion of erythrocytes by merozoites is an essential step for the survival and progression of malaria parasites. In order to invade red blood cells (RBCs), apicomplexan parasites have to adhere with their apex to the RBC membrane. This necessary apex-membrane contact (or alignment) is not immediately established, because the orientation of a free merozoite with respect to RBC membrane is random when an adhesion contact first occurs. Therefore, it has been suggested that after the initial adhesion, merozoites facilitate their proper alignment by inducing considerable membrane deformations, frequently observed before the invasion process. This proposition is based on a positive correlation between RBC membrane deformation and successful invasion; however, the role of RBC mechanics and its deformation in the alignment process remains elusive. Using a mechanically realistic model of a deformable RBC, we investigate numerically the importance of RBC deformability for merozoite alignment. Adhesion between the parasite and RBC membrane is modeled by an attractive potential which might be inhomogeneous, mimicking possible adhesion gradients at the surface of a parasite. Our results show that RBC membrane deformations are crucial for successful merozoite alignment, and require interaction strengths comparable to adhesion forces measured experimentally. Adhesion gradients along the parasite body further improve its alignment. Finally, an increased membrane rigidity is found to result in poor merozoite alignment, which can be a possible reason for a reduction in the invasion efficiency of RBCs in several blood diseases associated with membrane stiffening.〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Cell〈/p〉 〈p〉Author(s): Meng Xu, Hong-Hai Xu, Yuan Lin, Xiangnan Sun, Li-Jing Wang, Zhe-Ping Fang, Xue-Han Su, Xiang-Jing Liang, Yang Hu, Zhi-Min Liu, Yuanxiong Cheng, Yuanyuan Wei, Jiabin Li, Li Li, Hong-Juan Liu, Zhiqiang Cheng, Na Tang, Chao Peng, Tingting Li, Tengfei Liu〈/p〉 〈h5〉Summary〈/h5〉 〈div〉〈p〉Liver fibrosis is a very common condition seen in millions of patients with various liver diseases, and yet no effective treatments are available owing to poorly characterized molecular pathogenesis. Here, we show that leukocyte cell-derived chemotaxin 2 (LECT2) is a functional ligand of Tie1, a poorly characterized endothelial cell (EC)-specific orphan receptor. Upon binding to Tie1, LECT2 interrupts Tie1/Tie2 heterodimerization, facilitates Tie2/Tie2 homodimerization, activates PPAR signaling, and inhibits the migration and tube formations of EC. 〈em〉In vivo〈/em〉 studies showed that LECT2 overexpression inhibits portal angiogenesis, promotes sinusoid capillarization, and worsens fibrosis, whereas these changes were reversed in 〈em〉Lect2-KO〈/em〉 mice. Adeno-associated viral vector serotype 9 (AAV9)-LECT2 small hairpin RNA (shRNA) treatment significantly attenuates fibrosis. Upregulation of LECT2 is associated with advanced human liver fibrosis staging. We concluded that targeting LECT2/Tie1 signaling may represent a potential therapeutic target for liver fibrosis, and serum LECT2 level may be a potential biomarker for the screening and diagnosis of liver fibrosis.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S009286741930786X-fx1.jpg" width="375" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Cell〈/p〉 〈p〉Author(s): Francisco J. Roca, Laura J. Whitworth, Sarah Redmond, Ana A. Jones, Lalita Ramakrishnan〈/p〉 〈h5〉Summary〈/h5〉 〈div〉〈p〉Necrosis of infected macrophages constitutes a critical pathogenetic event in tuberculosis by releasing mycobacteria into the growth-permissive extracellular environment. In zebrafish infected with 〈em〉Mycobacterium marinum〈/em〉 or 〈em〉Mycobacterium tuberculosis〈/em〉, excess tumor necrosis factor triggers programmed necrosis of infected macrophages through the production of mitochondrial reactive oxygen species (ROS) and the participation of cyclophilin D, a component of the mitochondrial permeability transition pore. Here, we show that this necrosis pathway is not mitochondrion-intrinsic but results from an inter-organellar circuit initiating and culminating in the mitochondrion. Mitochondrial ROS induce production of lysosomal ceramide that ultimately activates the cytosolic protein BAX. BAX promotes calcium flow from the endoplasmic reticulum into the mitochondrion through ryanodine receptors, and the resultant mitochondrial calcium overload triggers cyclophilin-D-mediated necrosis. We identify ryanodine receptors and plasma membrane L-type calcium channels as druggable targets to intercept mitochondrial calcium overload and necrosis of mycobacterium-infected zebrafish and human macrophages.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S009286741930892X-fx1.jpg" width="375" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Cell〈/p〉 〈p〉Author(s): Gorka Lasso, Sandra V. Mayer, Evandro R. Winkelmann, Tim Chu, Oliver Elliot, Juan Angel Patino-Galindo, Kernyu Park, Raul Rabadan, Barry Honig, Sagi D. Shapira〈/p〉 〈h5〉Summary〈/h5〉 〈div〉〈p〉While knowledge of protein-protein interactions (PPIs) is critical for understanding virus-host relationships, limitations on the scalability of high-throughput methods have hampered their identification beyond a number of well-studied viruses. Here, we implement an 〈em〉in silico〈/em〉 computational framework (pathogen host interactome prediction using structure similarity [P-HIPSTer]) that employs structural information to predict ∼282,000 pan viral-human PPIs with an experimental validation rate of ∼76%. In addition to rediscovering known biology, P-HIPSTer has yielded a series of new findings: the discovery of shared and unique machinery employed across human-infecting viruses, a likely role for ZIKV-ESR1 interactions in modulating viral replication, the identification of PPIs that discriminate between human papilloma viruses (HPVs) with high and low oncogenic potential, and a structure-enabled history of evolutionary selective pressure imposed on the human proteome. Further, P-HIPSTer enables discovery of previously unappreciated cellular circuits that act on human-infecting viruses and provides insight into experimentally intractable viruses.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0092867419308931-fx1.jpg" width="375" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Cell〈/p〉 〈p〉Author(s): Sarah Canetta, Christoph Kellendonk〈/p〉 〈div〉〈p〉Can we one day prevent mental disorders? Mukherjee et al. (2019) use a genetic mouse model of schizophrenia-risk with established abnormalities in adult hippocampal-prefrontal circuit function and cognitive behaviors to identify circuit-specific treatments during adolescence that prevent the onset of the adult deficits.〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 29 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Cell〈/p〉 〈p〉Author(s): Jianke Gong, Jinzhi Liu, Elizabeth A. Ronan, Feiteng He, Wei Cai, Mahar Fatima, Wenyuan Zhang, Hankyu Lee, Zhaoyu Li, Gun-Ho Kim, Kevin P. Pipe, Bo Duan, Jianfeng Liu, X.Z. Shawn Xu〈/p〉 〈h5〉Summary〈/h5〉 〈div〉〈p〉In search of the molecular identities of cold-sensing receptors, we carried out an unbiased genetic screen for cold-sensing mutants in 〈em〉C. elegans〈/em〉 and isolated a mutant allele of 〈em〉glr-3〈/em〉 gene that encodes a kainate-type glutamate receptor. While glutamate receptors are best known to transmit chemical synaptic signals in the CNS, we show that GLR-3 senses cold in the peripheral sensory neuron ASER to trigger cold-avoidance behavior. GLR-3 transmits cold signals via G protein signaling independently of its glutamate-gated channel function, suggesting GLR-3 as a metabotropic cold receptor. The vertebrate GLR-3 homolog GluK2 from zebrafish, mouse, and human can all function as a cold receptor in heterologous systems. Mouse DRG sensory neurons express GluK2, and GluK2 knockdown in these neurons suppresses their sensitivity to cold but not cool temperatures. Our study identifies an evolutionarily conserved cold receptor, revealing that a central chemical receptor unexpectedly functions as a thermal receptor in the periphery.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0092867419308335-fx1.jpg" width="375" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 21 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Biophysical Journal〈/p〉 〈p〉Author(s): Orkide Ordu, Alexandra Lusser, Nynke H. Dekker〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Eukaryotic genomes are hierarchically organized into protein-DNA assemblies for compaction into the nucleus. Nucleosomes, with the (H3-H4)〈sub〉2〈/sub〉 tetrasome as a likely intermediate, are highly dynamic in nature by way of several different mechanisms. We have recently shown that tetrasomes spontaneously change the direction of their DNA wrapping between left- and right-handed conformations, which may prevent torque build-up in chromatin during active transcription or replication. DNA sequence has been shown to strongly affect nucleosome positioning throughout chromatin. It is not known, however, whether DNA sequence also impacts the dynamic properties of tetrasomes. To address this question, we examined tetrasomes assembled on a high-affinity DNA sequence using freely orbiting magnetic tweezers. In this context, we also studied the effects of mono- and divalent salts on the flipping dynamics. We found that neither DNA sequence nor altered buffer conditions affect overall tetrasome structure. In contrast, tetrasomes bound to high-affinity DNA sequences showed significantly altered flipping kinetics, predominantly via a reduction in the lifetime of the canonical state of left-handed wrapping. Increased mono- and divalent salt concentrations counteracted this behaviour. Thus, our study indicates that high-affinity DNA sequences impact not only the positioning of the nucleosome, but that they also endow the subnucleosomal tetrasome with enhanced conformational plasticity. This may provide a means to prevent histone loss upon exposure to torsional stress, thereby contributing to the integrity of chromatin at high-affinity sites.〈/p〉〈/div〉

Beschreibung: 〈p〉Publication date: Available online 21 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Biophysical Journal〈/p〉 〈p〉Author(s): Heiko Heerklotz, Erwin London〈/p〉