Abstract:
:The growth of actin filament networks is a fundamental biological process that drives a variety of cellular and intracellular motions. During motility, eukaryotic cells and intracellular pathogens are propelled by actin networks organized by nucleation-promoting factors that trigger the formation of nascent filaments off the side of existing filaments in the network. A Brownian ratchet (BR) mechanism has been proposed to couple actin polymerization to cellular movements, whereby thermal motions are rectified by the addition of actin monomers at the end of growing filaments. Here, by following actin-propelled microspheres using three-dimensional laser tracking, we find that beads adhered to the growing network move via an object-fluctuating BR. Velocity varies with the amplitude of thermal fluctuation and inversely with viscosity as predicted for a BR. In addition, motion is saltatory with a broad distribution of step sizes that is correlated in time. These data point to a model in which thermal fluctuations of the microsphere or entire actin network, and not individual filaments, govern motility. This conclusion is supported by Monte Carlo simulations of an adhesion-based BR and suggests an important role for membrane tension in the control of actin-based cellular protrusions.
journal_name
Proc Natl Acad Sci U S Aauthors
Shaevitz JW,Fletcher DAdoi
10.1073/pnas.0702601104subject
Has Abstractpub_date
2007-10-02 00:00:00pages
15688-92issue
40eissn
0027-8424issn
1091-6490pii
0702601104journal_volume
104pub_type
杂志文章abstract::Acquired immunity to Streptococcus pneumoniae (pneumococcus) has long been assumed to depend on the presence of anticapsular antibodies. We found, however, that colonization with live pneumococci of serotypes 6B, 7F, or 14 protected mice against recolonization by any of the serotypes and that protection from acquisiti...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0501254102
更新日期:2005-03-29 00:00:00
abstract::The swelling of secretory vesicles has been implicated in exocytosis, but the underlying mechanism of vesicle swelling remains largely unknown. Zymogen granules (ZGs), the membrane-bound secretory vesicles in exocrine pancreas, swell in response to GTP mediated by a G(alpha)i3 protein. Evidence is presented here that ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.072083499
更新日期:2002-04-02 00:00:00
abstract::Tc1-like transposable elements from teleost fish have been phylogenetically examined to determine the mechanisms involved in their evolution and conserved domains of function. We identified two new functional domains in these elements. The first is a bipartite nuclear localization signal, indicating that transposons c...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.93.10.5008
更新日期:1996-05-14 00:00:00
abstract::Motifs of neural circuitry seem surprisingly conserved over different areas of neocortex or of paleocortex, while performing quite different sensory processing tasks. This apparent paradox may be resolved by the fact that seemingly different problems in sensory information processing are related by transformations (ch...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.93.26.15440
更新日期:1996-12-24 00:00:00
abstract::A protein that specifically binds leukemia inhibitory factor (LIF) has been isolated from normal mouse serum by using four successive fractionation steps: chromatography on a LIF affinity matrix, anion-exchange chromatography, size-exclusion chromatography, and preparative native gel electrophoresis. The purified LIF-...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.89.18.8616
更新日期:1992-09-15 00:00:00
abstract::A stable complex between pentaammineruthenium(III) and histidine-33 in horse heart ferricytochrome c is formed in the reaction between aquopentaammineruthenium(II) and the protein at pH 7. HPLC of the tryptic hydrolysate of the modified protein was employed to identify the pentaammineruthenium binding site. Spectrosco...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.79.22.7052
更新日期:1982-11-01 00:00:00
abstract::Antimicrobial levels of reactive oxygen species (ROS) are produced by the mammalian host defense to kill invading bacteria and limit bacterial colonization. One main in vivo target of ROS is the thiol group of proteins. We have developed a quantitative thiol trapping technique termed OxICAT to identify physiologically...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0707723105
更新日期:2008-06-17 00:00:00
abstract::From 25 to 29 April 2020, the state of Indiana undertook testing of 3,658 randomly chosen state residents for the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, the agent causing COVID-19 disease. This was the first statewide randomized study of COVID-19 testing in the United States. Both PC...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.2013906118
更新日期:2021-02-02 00:00:00
abstract::Lipoprotein oxidation is thought to play a pivotal role in atherogenesis, yet the underlying reaction mechanisms remain poorly understood. We have explored the possibility that high density lipoprotein (HDL) might be oxidized by peroxidase-generated tyrosyl radical. Exposure of HDL to L-tyrosine, H2O2, and horseradish...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.90.14.6631
更新日期:1993-07-15 00:00:00
abstract::Protein synthesis initiation in reticulocyte lysates is inhibited by heme deficiency, low levels of double-stranded RNA (dsRNA), oxidized glutathione (GSSG), or the purified kinase (HRI) that acts on the alpha polypeptide of eukaryotic initiation factor 2 (eIF-2alpha). The phosphoprotein profiles produced in lysates i...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.76.5.2118
更新日期:1979-05-01 00:00:00
abstract::Biomass burning drives changes in greenhouse gases, climate-forcing aerosols, and global atmospheric chemistry. There is controversy about the magnitude and timing of changes in biomass burning emissions on millennial time scales from preindustrial to present and about the relative importance of climate change and hum...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1807172115
更新日期:2018-12-04 00:00:00
abstract::Pseudoxanthoma elasticum (PXE) is an autosomal recessive disease characterized by progressive ectopic mineralization of the skin, eyes, and arteries, for which no effective treatment exists. PXE is caused by inactivating mutations in the gene encoding ATP-binding cassette sub-family C member 6 (ABCC6), an ATP-dependen...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1319582110
更新日期:2013-12-10 00:00:00
abstract::Alcohol exposure during development can cause brain malformations and neurobehavioral abnormalities. In view of the teratogenicity of ethanol, identification of molecules that could counteract the neurotoxic effects of alcohol deserves high priority. Here, we report that pituitary adenylate cyclase-activating polypept...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.082112699
更新日期:2002-04-30 00:00:00
abstract::beta-Adrenergic receptors on Friend erythroleukemic cells were identified by the use of 125I-labeled hydroxybenzylpindolol, a potent beta-adrenergic antagonist. Binding of this ligand was saturable and stereospecific. The relative orders of potency of isoproterenol, epinephrine, and norepinephrine to displace bound hy...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.77.7.4065
更新日期:1980-07-01 00:00:00
abstract::Cellular wound healing or the repair of plasma membrane/cell wall damage (plasma membrane damage) occurs frequently in nature. Although various cellular perturbations, such as DNA damage, spindle misalignment, and impaired daughter cell formation, are monitored by cell cycle checkpoint mechanisms in budding yeast, whe...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1523824113
更新日期:2016-06-21 00:00:00
abstract::Neurons vary in their capacity to produce, store, and release neuropeptides packaged in dense-core vesicles (DCVs). Specifically, neurons used for cotransmission have terminals that contain few DCVs and many small synaptic vesicles, whereas neuroendocrine neuron terminals contain many DCVs. Although the mechanistic ba...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1322170111
更新日期:2014-03-04 00:00:00
abstract::In clinical trials comparing two treatments, one would often like to control the probability of erroneous decision while minimizing not the total sample size but the number of patients given the inferior treatment. To do this obviously requires that one use a datadependent allocation rule for the two treatments rather...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 临床试验,杂志文章
doi:10.1073/pnas.69.10.2993
更新日期:1972-10-01 00:00:00
abstract::Immediately after adsorption, phages T4 and T5 induce a partial depolarization of the host cytoplasmic membrane. Infected bacteria respond to this phage-induced effect by a repolarization that leads to a new steady state of reduced membrane potential. The rate and extent of repolarization are adjusted to the intensity...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.78.1.215
更新日期:1981-01-01 00:00:00
abstract::The protein encoded by the neu protooncogene (human gene symbol NGL for neuro/glioblastoma-derived) is a member of the surface receptor/tyrosine kinase family. Though its structure suggests that it can transduce a transmembrane signal, neither its extracellular ligand nor its critical intracellular substrates are know...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.85.21.8057
更新日期:1988-11-01 00:00:00
abstract::Species- and strain-specific spontaneously occurring tumors have been observed in rodents maintained under normal laboratory conditions. Elucidation of the molecular mechanisms associated with the development of these spontaneous tumors may provide a better understanding of tumor development associated with exposure t...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.83.1.33
更新日期:1986-01-01 00:00:00
abstract::Cells from the spleens and thymuses of BALB/c mice whose Moloney sarcoma virus (MSV)-induced, primary sarcomas have regressed 2-3 months earlier ("MSV regressors") or are in the process of regressing can, when adoptively transferred to syngeneic mice given MSV at the age of 20 days, prevent the natural regression of t...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.76.10.5294
更新日期:1979-10-01 00:00:00
abstract::Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub-100-fs range. At the same time, much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1522265113
更新日期:2016-03-15 00:00:00
abstract::Interleukin 3 (IL-3) is a hematopoietic growth factor that supports the proliferation and differentiation of early hematopoietic-lineage progenitors. By using growth factor-dependent cell lines, IL-3 has been shown to induce the appearance of several phosphotyrosine-containing proteins, including a 140-kDa cell surfac...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.85.21.7982
更新日期:1988-11-01 00:00:00
abstract::Maximum likelihood analysis for linkage between autosomal dominant aniridia and 12 biochemical and serological markers in a single large family showed a probable linkage between autosomal dominant aniridia and the enzyme acid phosphatase-1. The presence of an autosomal dominant aniridia gene linked to acid phosphatase...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.77.3.1580
更新日期:1980-03-01 00:00:00
abstract::The BTB domain (also known as the POZ domain) is an evolutionarily conserved protein-protein interaction motif found at the N terminus of 5-10% of C2H2-type zinc-finger transcription factors, as well as in some actin-associated proteins bearing the kelch motif. Many BTB proteins are transcriptional regulators that med...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.95.21.12123
更新日期:1998-10-13 00:00:00
abstract::Insect molting and metamorphosis are induced by steroid hormones named ecdysteroids, whose production is regulated by various neuropeptides. We cloned the gene and analyzed the expression of the prothoracicostatic peptide, a unique neuropeptide shown to suppress the production of ecdysteroids in the prothoracic gland ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0907471107
更新日期:2010-02-02 00:00:00
abstract::Deletion derivatives of the maize transposable element Activator (Ac) were constructed in vitro and inserted into a kanamycin resistance gene. These constructions were then introduced into tobacco protoplasts derived from plants previously transformed with Ac. The ability of each deletion derivative to excise was meas...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.86.23.9385
更新日期:1989-12-01 00:00:00
abstract::III-V compound semiconductors are widely used for electronic and optoelectronic applications. However, interfacing III-Vs with other materials has been fundamentally limited by the high growth temperatures and lattice-match requirements of traditional deposition processes. Recently, we developed the templated liquid-p...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1915786117
更新日期:2020-01-14 00:00:00
abstract::During the last 15 years several laboratories have attempted to generate rabbit monoclonal antibodies, mainly because rabbits recognize antigens and epitopes that are not immunogenic in mice or rats, two species from which monoclonal antibodies are usually generated. Monoclonal antibodies from rabbits could not be gen...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.92.20.9348
更新日期:1995-09-26 00:00:00
abstract::Activation energies for the individual steps of secretory and viral fusion are reported to be large [Oberhauser, A. F., Monck, J. R. & Fernandez, J. M. (1992) Biophys. J. 61, 800-809; Clague, M. J., Schoch, C., Zech, L. & Blumenthal, R. (1990) Biochemistry 29, 1303-1308]. Understanding the cause for these large activa...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.95.16.9274
更新日期:1998-08-04 00:00:00