113 research outputs found
Arabidopsis SYT1 maintains stability of cortical endoplasmic reticulum networks and VAP27-1-enriched endoplasmic reticulumâplasma membrane contact sites
Arabidopsis synaptotagmin 1 (SYT1) is localized on the endoplasmic reticulumâplasma membrane (ERâPM) contact sites in leaf and root cells. The ERâPM localization of Arabidopsis SYT1 resembles that of the extended synaptotagmins (E-SYTs) in animal cells. In mammals, E-SYTs have been shown to regulate calcium signaling, lipid transfer, and endocytosis. Arabidopsis SYT1 was reported to be essential for maintaining cell integrity and virus movement. This study provides detailed insight into the subcellular localization of SYT1 and VAP27-1, another ERâPM-tethering protein. SYT1 and VAP27-1 were shown to be localized on distinct ERâPM contact sites. The VAP27-1-enriched ERâPM contact sites (V-EPCSs) were always in contact with the SYT1-enriched ERâPM contact sites (S-EPCSs). The V-EPCSs still existed in the leaf epidermal cells of the SYT1 null mutant; however, they were less stable than those in the wild type. The polygonal networks of cortical ER disassembled and the mobility of VAP27-1 protein on the ERâPM contact sites increased in leaf cells of the SYT1 null mutant. These results suggest that SYT1 is responsible for stabilizing the ER network and V-EPCSs
Actin3 promoter reveals undulating F-actin bundles at shanks and dynamic F-actin meshworks at tips of tip-growing pollen tubes
The dynamic actin cytoskeleton of pollen tubes is both the driver of the tip growth and the organizer of cell polarity. In order to understand this fast re-arranging cytoskeletal system, we need reliable constructs expressed under relevant promoters. Here we are reporting that the Lifeact reporter, expressed under the pollen-specific Actin3 promoter, visualizes very dynamic F-actin elements both in germinating pollen grains and tip-growing pollen tubes. Importantly, we have documented very active actin polymerization at the cell periphery, especially in the bulging area during pollen germination and in the apical clear zone. Expression of the Lifeact reporter under control of the pollen-specific Actin3 promoter revealed 2 new aspects: (i) long F-actin bundles in pollen tube shanks are dynamic, showing undulating movements, (ii) subapical âactin collarsâ or âfringesâ are absent
External Device to Incrementally Skid the Habitat (E-DISH)
A Mars habitat transport system was designed as part of the NASA Mars exploration program. The transport system, the External Device to Incrementally Skid the Habitat (E - DISH), will be used to transport Mars habitats from their landing sites to the colony base and will be detached after unloading. The system requirements for Mars were calculated and scaled for model purposes. Specific model materials are commonly found and recommendations for materials for the Mars design are included
Endocytosis of BRASSINOSTEROID INSENSITIVE1 is partly driven by a canonical tyr-based motif
Clathrin-mediated endocytosis (CME) and its core endocytic machinery are evolutionarily conserved across all eukaryotes. In mammals, the heterotetrameric adaptor protein complex-2 (AP-2) sorts plasma membrane (PM) cargoes into vesicles through the recognition of motifs based on tyrosine or di-leucine in their cytoplasmic tails. However, in plants, very little is known on how PM proteins are sorted for CME and whether similar motifs are required. In Arabidopsis thaliana, the brassinosteroid (BR) receptor, BR INSENSITIVE1 (BRI1), undergoes endocytosis that depends on clathrin and AP-2. Here we demonstrate that BRI1 binds directly to the medium AP-2 subunit, AP2M. The cytoplasmic domain of BRI1 contains five putative canonical surface-exposed tyrosine-based endocytic motifs. The tyrosine-to-phenylalanine substitution in Y898KAI reduced BRI1 internalization without affecting its kinase activity. Consistently, plants carrying the BRI1Y898F mutation were hypersensitive to BRs. Our study demonstrates that AP-2-dependent internalization of PM proteins via the recognition of functional tyrosine motifs also operates in plants
Dimensional control and morphological transformations of supramolecular polymeric nanofibers based on cofacially-stacked planar amphiphilic platinum(II) complexes
Square-planar
platinumÂ(II) complexes often stack cofacially to
yield supramolecular fiber-like structures with interesting photophysical
properties. However, control over fiber dimensions and the resulting
colloidal stability is limited. We report the self-assembly of amphiphilic
PtÂ(II) complexes with solubilizing ancillary ligands based on polyethylene
glycol [PEG<sub><i>n</i></sub>, where <i>n</i> = 16, 12, 7]. The complex with the longest solubilizing PEG ligand, <b>Pt-PEG</b><sub><b>16</b></sub>, self-assembled to form polydisperse
one-dimensional (1D) nanofibers (diameters <5 nm). Sonication led
to short seeds which, on addition of further molecularly dissolved <b>Pt-PEG</b><sub><b>16</b></sub> complex, underwent elongation
in a âliving supramolecular polymerizationâ process
to yield relatively uniform fibers of length up to <i>ca</i>. 400 nm. The fiber lengths were dependent on the <b>Pt-PEG</b><sub><b>16</b></sub> complex to seed mass ratio in a manner
analogous to a living covalent polymerization of molecular monomers.
Moreover, the fiber lengths were unchanged in solution after 1 week
and were therefore âstaticâ with respect to interfiber
exchange processes on this time scale. In contrast, similarly formed
near-uniform fibers of <b>Pt-PEG</b><sub><b>12</b></sub> exhibited dynamic behavior that led to broadening of the length
distribution within 48 h. After aging for 4 weeks in solution, <b>Pt-PEG</b><sub><b>12</b></sub> fibers partially evolved
into 2D platelets. Furthermore, self-assembly of <b>Pt-PEG</b><sub><b>7</b></sub> yielded only transient fibers which rapidly
evolved into 2D platelets. On addition of further fiber-forming Pt
complex (<b>Pt-PEG</b><sub><b>16</b></sub>), the platelets
formed assemblies <i>via</i> the growth of fibers selectively
from their short edges. Our studies demonstrate that when interfiber
dynamic exchange is suppressed, dimensional control and hierarchical
structure formation are possible for supramolecular polymers through
the use of kinetically controlled seeded growth methods
Butyrophilin-like 2 regulates site-specific adaptations of intestinal γΎ intraepithelial lymphocytes
Tissue-resident γΎ intraepithelial lymphocytes (IELs) orchestrate innate and adaptive immune responses to maintain intestinal epithelial barrier integrity. Epithelia-specific butyrophilin-like (Btnl) molecules induce perinatal development of distinct Vγ TCR+ IELs, however, the mechanisms that control γΎ IEL maintenance within discrete intestinal segments are unclear. Here, we show that Btnl2 suppressed homeostatic proliferation of γΎ IELs preferentially in the ileum. High throughput transcriptomic characterization of site-specific Btnl2-KO γΎ IELs reveals that Btnl2 regulated the antimicrobial response module of ileal γΎ IELs. Btnl2 deficiency shapes the TCR specificities and TCRγ/Ύ repertoire diversity of ileal γΎ IELs. During DSS-induced colitis, Btnl2-KO mice exhibit increased inflammation and delayed mucosal repair in the colon. Collectively, these data suggest that Btnl2 fine-tunes γΎ IEL frequencies and TCR specificities in response to site-specific homeostatic and inflammatory cues. Hence, Btnl-mediated targeting of γΎ IEL development and maintenance may help dissect their immunological functions in intestinal diseases with segment-specific manifestations
Application of Plasticity Theory to Reinforced Concrete Deep Beams
yesThis paper reviews the application of the plasticity theory to reinforced concrete deep beams. Both the truss analogy and mechanism approach were employed to predict the capacity of reinforced concrete deep beams. In addition, most current codes of practice, for example Eurocode 1992 and ACI 318-05, recommend the strut-and-tie model for designing reinforced concrete deep beams.
Compared with methods based on empirical or semi-empirical equations, the strut-and-tie model and mechanism analyses are more rational, adequately accurate and sufficiently simple for estimating the load capacity of reinforced concrete deep beams. However, there is a problem of selecting the effectiveness factor of concrete as reflected in the wide range of values reported in the literature for deep beams
Neural network modelling of RC deep beam shear strength
YesA 9 x 18 x 1 feed-forward neural network (NN) model
trained using a resilient back-propagation algorithm and
early stopping technique is constructed to predict the
shear strength of deep reinforced concrete beams. The
input layer covering geometrical and material properties
of deep beams has nine neurons, and the corresponding output is the shear strength. Training, validation and testing of the developed neural network have been
achieved using a comprehensive database compiled from
362 simple and 71 continuous deep beam specimens.
The shear strength predictions of deep beams obtained
from the developed NN are in better agreement with
test results than those determined from strut-and-tie
models. The mean and standard deviation of the ratio between predicted capacities using the NN and measured shear capacities are 1.028 and 0.154, respectively, for simple deep beams, and 1.0 and 0.122, respectively, for continuous deep beams. In addition, the
trends ascertained from parametric study using the developed NN have a consistent agreement with those observed in other experimental and analytical investigations
Tuftsin Promotes an Anti-Inflammatory Switch and Attenuates Symptoms in Experimental Autoimmune Encephalomyelitis
Multiple sclerosis (MS) is a demyelinating autoimmune disease mediated by infiltration of T cells into the central nervous system after compromise of the blood-brain barrier. We have previously shown that administration of tuftsin, a macrophage/microglial activator, dramatically improves the clinical course of experimental autoimmune encephalomyelitis (EAE), a well-established animal model for MS. Tuftsin administration correlates with upregulation of the immunosuppressive Helper-2 Tcell (Th2) cytokine transcription factor GATA-3. We now show that tuftsin-mediated microglial activation results in shifting microglia to an anti-inflammatory phenotype. Moreover, the T cell phenotype is shifted towards immunoprotection after exposure to tuftsin-treated activated microglia; specifically, downregulation of pro-inflammatory Th1 responses is triggered in conjunction with upregulation of Th2-specific responses and expansion of immunosuppressive regulatory T cells (Tregs). Finally, tuftsin-shifted T cells, delivered into animals via adoptive transfer, reverse the pathology observed in mice with established EAE. Taken together, our findings demonstrate that tuftsin decreases the proinflammatory environment of EAE and may represent a therapeutic opportunity for treatment of MS
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