scholarly journals Asymmetric Tug-of-War leads to Cooperative Transport of a Cargo by Multiple Kinesins

2019 ◽  
Author(s):  
Marco Tjioe ◽  
Saurabh Shukla ◽  
Rohit Vaidya ◽  
Alice Troitskaia ◽  
Carol Bookwalter ◽  
...  
Keyword(s):  
Small Groups ◽  
Molecular Motor ◽  
Primary Role ◽  
Forward Motion ◽  
Cooperative Motion ◽  
Cellular Environment ◽  
Cooperative Transport ◽  
Develop Tension

AbstractHow cargoes move within a crowded cell—over long distances and at speeds that are nearly the same as when moving on an unimpeded pathway—has long been mysterious. Through an in vitro gliding assay, which involves measuring nanometer displacement and piconewtons of force, we have evidence that when kinesins, a cytoplasmic molecular motor, operate in small groups, from 2-10, they can communicate among themselves through an asymmetric tug-of-war by inducing tension (up to 4 pN) on the cargo. Surprisingly, the primary role of approximately one-third of kinesins is to develop tension, which instantaneously slows forward motion but helps increase cargo run length. These hindering kinesins fall off rapidly when experiencing a forward tug. Occasionally, they may be ripped off from their anchors by other driving kinesins working in tandem. Furthermore, with roadblocks on the microtubule, multiple kinesins cooperate to overcome impediments. Hence, kinesin may employ an asymmetric tug-of-war and a cooperative motion to navigate through cellular environment.

scholarly journals Membrane-associated phase separation: organization and function emerge from a two-dimensional milieu

2021 ◽  
Author(s):  
Jonathon A Ditlev
Keyword(s):  
Phase Separation ◽  
Cell Biology ◽  
Cellular Environment ◽  
Condensate Formation ◽  
Associated Proteins ◽  
Available Technology ◽  
And Function ◽  
Surrounding Membrane

Abstract Liquid‒liquid phase separation (LLPS) of biomolecules has emerged as an important mechanism that contributes to cellular organization. Phase separated biomolecular condensates, or membrane-less organelles, are compartments composed of specific biomolecules without a surrounding membrane in the nucleus and cytoplasm. LLPS also occurs at membranes, where both lipids and membrane-associated proteins can de-mix to form phase separated compartments. Investigation of these membrane-associated condensates using in vitro biochemical reconstitution and cell biology has provided key insights into the role of phase separation in membrane domain formation and function. However, these studies have generally been limited by available technology to study LLPS on model membranes and the complex cellular environment that regulates condensate formation, composition, and function. Here, I briefly review our current understanding of membrane-associated condensates, establish why LLPS can be advantageous for certain membrane-associated condensates, and offer a perspective for how these condensates may be studied in the future.

Role of fatty acid oxidation in mechanism of action of gastric secretagogues

1980 ◽  
Vol 238 (3) ◽  
pp. G255-G262
Author(s):  
J. Chacin ◽  
G. Martinez ◽  
E. Severin
Keyword(s):  
Fatty Acid ◽  
Gastric Mucosa ◽  
Acid Secretion ◽  
Fatty Acid Oxidation ◽  
Acid Oxidation ◽  
Primary Role ◽  
Dependent Manner ◽  
Beta Oxidation

The role of beta-oxidation in the mechanism of stimulation of acid secretion was examined in toad gastric mucosa in vitro. The incubation with 4-pentenoate selectively inhibited in a dose-dependent manner the rate of 14CO2 formation from [1-14C]octanoate. Pretreatment with 20 mM 4-pentenoate sharply reduced the respiratory and secretory responses to theophylline and histamine. Tracer studies showed a major utilization of exogenous octanoate over glucose and pyruvate by the in vitro toad gastric mucosa. Theophylline and histamine stimulated by 69% the rate of octanoate oxidation. Over 60% of the increments in oxygen uptake produced by theophylline and histamine accounted for the increments in octanoate oxidation, whereas glucose and pyruvate together accounted for less than 25%. Octanoate-dependent respiration was shown to correlate with octanoate oxidation under both inhibition with 4-pentenoate and stimulation with theophylline. Theophylline stimulated by 25% the rate of octanoate oxidation in Cl--free glucuronate-nutrient solutions. The present work provides further evidence for the primary role of fatty acid oxidation in the mechanism of acid secretion in amphibian.

scholarly journals Influenza virus-specific CD4+ T helper type 2 T lymphocytes do not promote recovery from experimental virus infection.

1994 ◽  
Vol 180 (4) ◽  
pp. 1273-1282 ◽  
Author(s):  
M B Graham ◽  
V L Braciale ◽  
T J Braciale
Keyword(s):  
Immune Response ◽  
T Cells ◽  
T Lymphocytes ◽  
Cd4 T Cells ◽  
Primary Role ◽  
T Helper ◽  
Helper Type

T lymphocytes play a primary role in recovery from viral infections and in antiviral immunity. Although viral-specific CD8+ and CD4+ T cells have been shown to be able to lyse virally infected targets in vitro and promote recovery from lethal infection in vivo, the role of CD4+ T lymphocytes and their mechanism(s) of action in viral immunity are not well understood. The ability to further dissect the role that CD4+ T cells play in the immune response to a number of pathogens has been greatly enhanced by evidence for more extensive heterogeneity among the CD4+ T lymphocytes. To further examine the role of CD4+ T cells in the immune response to influenza infection, we have generated influenza virus-specific CD4+ T cell clones from influenza-primed BALB/c mice with differential cytokine secretion profiles that are defined as T helper type 1 (Th1) clones by the production of interleukin 2 (IL-2) and interferon gamma (IFN-gamma), or as Th2 clones by the production of IL-4, IL-5, and IL-10. Our studies have revealed that Th1 clones are cytolytic in vitro and protective against lethal challenge with virus in vivo, whereas Th2 clones are noncytolytic and not protective. Upon further evaluation of these clonal populations we have shown that not only are the Th2 clones nonprotective, but that pulmonary pathology is exacerbated as compared with control mice as evidenced by delayed viral clearance and massive pulmonary eosinophilia. These data suggest that virus-specific CD4+ T cells of the Th2 subset may not play a primary role in virus clearance and recovery and may lead to immune mediated potentiation of injury.

AlphaVBeta3 (αvβ3) Integrin Drives the Osteoclastogenesis through a Osteoclast-Like Functional Differentiation of Myeloma Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 814-814 ◽  
Author(s):  
Marco Tucci ◽  
Lucia Lombardi ◽  
Steve Reshkin ◽  
Rosa A. Cardone ◽  
Silvestris Franco
Keyword(s):  
Bone Erosion ◽  
Bone Lesions ◽  
Αvβ3 Integrin ◽  
Primary Role ◽  
Myeloma Cells ◽  
Group A ◽  
Group B ◽  
Rpmi 8226

Abstract Accelerated osteoclastogenesis is the major event promoting the skeletal impairment in multiple myeloma (MM). Osteoclasts (OC) are directly activated by myeloma cells (MC), although these cells themselves may apparently undergo to OC-like morphologic transformation and produce bone erosion in vitro. Since OCs exert their function and promote osteoclastogenesis through activation of several adhesion molecules, including avb3, we investigated the role of this integrin expressed by MCs in their OC-like activity in vitro. Bone marrow MCs were purified from eight patients with severe skeletal disease (group A) and from two patients without bone lesions (group B). U266 and RPMI-8226 MC lines were the controls. Semi-nested PCR assessed the CDR3 immunoglobulin (Ig) gene rearrangement, whereas OC markers including TRAcP, cathepsin-k, calcitonin-receptor, carbonic anhydrase and vATPase were evaluated by RT-PCR. The cytoskeletal rearrangement of F-actin was analyzed by immunofluorescence. av and b3 expression on MCs was evaluated by flow-cytometry, whereas bone erosion on calcium phosphate discs and number of pits was measured by dedicated software. The effect of avb3 stimulation on the activation of osteoclastogenic function was investigated by exploring the phosphorilation of transcriptional kinases and downstream molecules, as ERK1/2 and cFos, respectively. The primary role of avb3 in OC-like functional transdifferentiation was explored in MCs by siRNA silencing for both chains. Ontogenetic derivation from the B-cell lineage was confirmed by the monoclonal CDR3 rearrangement, CD138/CD38 and Pax-5 expression. Cells from patients of group A expressed OC markers, in contrast with those of group B or U266 and RPMI-8226. Formation of the F-actin ring confirmed the differentiation of MCs toward the OC-like phenotype. Cells from group A expressed av and b3 (80±7% and 75±9%) similarly to U266 and RPMI-8226 (>90% in both instances), whereas a minimal expression was demonstrated in group B (av:6±2%; b3:8±3%). avb3+ cells produced a high number of erosive pits, at variance from avb3− cells (35±8 vs. 4±1 pits/cm2 ). The highest phosphorilation of ERK1/2 and expression of cFos was revealed in patients of group A as compared to B (840±110 OD and 905±210 OD vs. 270±35 OD and 315±80 OD, p<0.0001 in both instances). Finally, the silencing of av and/or b3 chain inhibited the erosion by avb3+ cells, resulting in a reduced number of pits (7±2 pits/cm2) similar to the pattern obtained with avb3− cells. Similarly, an inhibition of both ERK1/2 and cFos was demonstrated in silenced cells from group A with values similar to those of group B. Since avb3 drives both adhesion of Ocs to extracellular matrix and activation of osteoclastogenesis, it is conceivable that avb3+ MCs may functionally transdifferentiate to OCs in response to integrin activation induced by the contact with stromal cells within the marrow environment, thus resulting in a typical OC-like behaviour. In addition, our data suggest that MCs induce this effect by avb3, since its silencing reduces the OC-like activity in vitro.

scholarly journals Influence of fibrinolitic potential reduction in ischemic brain disease development

2008 ◽  
Vol 61 (5-6) ◽  
pp. 247-251 ◽  
Author(s):  
Biljana Vuckovic ◽  
Mirjana Djeric ◽  
Marija Zarkov
Keyword(s):  
Plasminogen Activator ◽  
Brain Disease ◽  
Fibrinolytic System ◽  
Brain Diseases ◽  
Primary Role ◽  
Plasminogen Activator Inhibitor 1 ◽  
Ischemic Brain ◽  
Pai 1

Introduction Vascular brain diseases are the third leading cause of morbidity and mortality today. Among them ischemic brain disease caused mostly by cerebral atherosclerosis makes almost 80%. The main risk factors for this disease are arterial hypertension, dislipoproteinemia and diabetes but, recently hemostatic system disorders have also been underlined, especially fibrinolytic disorders. Physiology of fibrinolysis The primary role of fibrinolytic system is to make blood vessels passable by prevention of thromb forming or by removing the existing ones. This role is enabled by constant dynamic balance between activators and inhibitors of fibrinolysis. The leading activators are tissue plasminogen activator (t-PA) and urokinase plasminogen activator (u-PA) and the most important inhibitors are 2-antiplasmin, plasminogen activator inhibitor 1 (PAI-1) and thrombin activated fibrinolytic inhibitor (TAFI). Fibrinolysis and thrombosis In patients with atherosclerosis there is clear insufficiency of fibrinolysis caused mainly by the increased activity of fibrinolytic inhibitors. There is evidence that the level of PAI-1 connected to fibrin directly affects thromb resistance to fibrinolysis and that velocity of thromb lysis in vitro predominantly depends on TAFI concentration. Factor XIII also has influence on thromb structure and stability and Lp(a) lipoprotein is one more factor that is responsible for resistency of thromb to fibrinolysis. Fibrinolysis in ischemic brain disease Reduced fibrinolytic capacity is noticed in patients with ischemic brain disease resulting from the increased PAI-1 activity. Higher risk for ischemic brain disease is verified among people with 4G/4G PAI-1 genotype. Raised level of t-PA antigene can also induce reduction of endogenous fibrinolysis. Conclusion In conclusion we want to underline that a possible pathophysiological significance of fibrinolytic system is assumed in a high percentage of patients with ischemic brain disease. Because of that we need further investigations to establish precise role of fibrinolytic mechanisms in genesis of this disease.

Actin Dynamics, Architecture, and Mechanics in Cell Motility

2014 ◽  
Vol 94 (1) ◽  
pp. 235-263 ◽  
Author(s):  
Laurent Blanchoin ◽  
Rajaa Boujemaa-Paterski ◽  
Cécile Sykes ◽  
Julie Plastino
Keyword(s):  
Mechanical Properties ◽  
Actin Filaments ◽  
Molecular Motor ◽  
Actin Dynamics ◽  
Tight Coupling ◽  
Actin Organization ◽  
Cellular Processes ◽  
Shock Absorbers ◽  
Cellular Environment

Tight coupling between biochemical and mechanical properties of the actin cytoskeleton drives a large range of cellular processes including polarity establishment, morphogenesis, and motility. This is possible because actin filaments are semi-flexible polymers that, in conjunction with the molecular motor myosin, can act as biological active springs or “dashpots” (in laymen's terms, shock absorbers or fluidizers) able to exert or resist against force in a cellular environment. To modulate their mechanical properties, actin filaments can organize into a variety of architectures generating a diversity of cellular organizations including branched or crosslinked networks in the lamellipodium, parallel bundles in filopodia, and antiparallel structures in contractile fibers. In this review we describe the feedback loop between biochemical and mechanical properties of actin organization at the molecular level in vitro, then we integrate this knowledge into our current understanding of cellular actin organization and its physiological roles.

NO overproduction by eNOS precedes hyperdynamic splanchnic circulation in portal hypertensive rats

1999 ◽  
Vol 276 (4) ◽  
pp. G1043-G1051 ◽  
Author(s):  
Reiner Wiest ◽  
Vijay Shah ◽  
William C. Sessa ◽  
Roberto J. Groszmann
Keyword(s):  
Splanchnic Circulation ◽  
Mesenteric Arteries ◽  
Primary Role ◽  
Hypertensive Rats ◽  
Protein Levels ◽  
No Release ◽  
Before And After ◽  
Enos Protein

Chronic high blood flow and the hyperdynamic circulatory syndrome in portal hypertension are associated with endothelial constitutive nitric oxide (NO) synthase (eNOS) upregulation and increased NO release. In portal vein-ligated (PVL) rats the splanchnic circulation is not yet hyperdynamic on day 3 postoperatively. In vitro perfused superior mesenteric arteries (SMAs) of day 3PVL and sham rats were challenged with increasing flow rates or the α-adrenoreceptor agonist methoxamine (30 and 100 μM) before and after incubation with the NO inhibitor, N ω-nitro-l-arginine (l-NNA, 10−4 M). Perfusate NO metabolite (NO x ) concentrations were measured by chemiluminescence. PVL rats expressed a significant hyporesponsiveness to increases in flow rate or methoxamine that was overcome by incubation with l-NNA. The PVL vasculature showed significantly higher slopes of NO x production vs. flow-induced shear stress, higher increases in perfusate NO x concentration in response to methoxamine, and higher eNOS protein levels (Western blot) compared with sham rats. In conclusion, eNOS-upregulation and increased NO release by the SMA endothelium occur before the development of the hyperdynamic splanchnic circulation, suggesting a primary role of NO in the pathogenesis of arterial vasodilatation.

scholarly journals Investigation of New Orexin 2 Receptor Modulators Using In Silico and In Vitro Methods

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2926 ◽  
Author(s):  
Jana Janockova ◽  
Rafael Dolezal ◽  
Eugenie Nepovimova ◽  
Tereza Kobrlova ◽  
Marketa Benkova ◽  
...  
Keyword(s):  
Intrinsic Activity ◽  
Primary Role ◽  
Orexin A ◽  
Orexin Receptors ◽  
Brain Barrier Permeability ◽  
Excitatory Neurotransmitters ◽  
G Protein Coupled

The neuropeptides, orexin A and orexin B (also known as hypocretins), are produced in hypothalamic neurons and belong to ligands for orphan G protein-coupled receptors. Generally, the primary role of orexins is to act as excitatory neurotransmitters and regulate the sleep process. Lack of orexins may lead to sleep disorder narcolepsy in mice, dogs, and humans. Narcolepsy is a neurological disorder of alertness characterized by a decrease of ability to manage sleep-wake cycles, excessive daytime sleepiness, and other symptoms, such as cataplexy, vivid hallucinations, and paralysis. Thus, the discovery of orexin receptors, modulators, and their causal implication in narcolepsy is the most important advance in sleep-research. The presented work is focused on the evaluation of compounds L1–L11 selected by structure-based virtual screening for their ability to modulate orexin receptor type 2 (OX2R) in comparison with standard agonist orexin-A together with their blood-brain barrier permeability and cytotoxicity. We can conclude that the studied compounds possess an affinity towards the OX2R. However, the compounds do not have intrinsic activity and act as the antagonists of this receptor. It was shown that L4 was the most potent antagonistic ligand to orexin A and displayed an IC50 of 2.2 µM, offering some promise mainly for the treatment of insomnia.

scholarly journals A counter-enzyme complex regulates glutamate metabolism in Bacillus subtilis

2021 ◽  
Author(s):  
Vijay Jayaraman ◽  
D. John Lee ◽  
Nadav Elad ◽  
Shay Vimer ◽  
Michal Sharon ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Glutamate Synthase ◽  
Enzyme Complex ◽  
Primary Role ◽  
Biofilm Growth ◽  
Rich Media ◽  
Sequential Reactions

Multi-enzyme assemblies composed of metabolic enzymes catalyzing sequential reactions are being increasingly studied. Here, we report the discovery of a 1.6 megadalton multi-enzyme complex from Bacillus subtilis composed of two enzymes catalyzing opposite rather than sequential reactions (counter-enzymes): glutamate synthase (GltAB), and glutamate dehydrogenase (GudB), that make and break glutamate, respectively. In vivo and in vitro studies show that the primary role of complex formation is to inhibit GudBs activity as this enzyme is constitutively expressed including in glutamate-limiting conditions. Using cryo-electron microscopy, we elucidated the structure of the complex and the basis of GudBs inhibition. Finally, we show that this complex that exhibits unusual oscillatory progress curves is a necessity for planktonic growth in glutamate-limiting conditions, but is also essential for biofilm growth in glutamate-rich media, suggesting a regulatory role at fluctuating glutamate concentrations.

Prostaglandins and Platelet Aggregation in Vivo

1970 ◽  
Vol 23 (02) ◽  
pp. 293-298 ◽  
Author(s):  
J Kloeze
Keyword(s):  
Platelet Aggregation ◽  
Prostaglandin E1 ◽  
Blood Platelets ◽  
Adenosine Diphosphate ◽  
Primary Role ◽  
Electric Stimulus ◽  
Platelet Thrombi

SummaryIt was shown previously that prostaglandin E1 (PGE1) inhibits the aggregation of blood platelets in vitro whereas PGF1α does not; in vivo, PGE1 inhibits in rats the action of intravenously injected adenosine diphosphate. Locally administered PGE1 is found in the present experiment to inhibit in rats the formation and growth of platelet thrombi, induced by an electric stimulus in cortical veins. PGF1α appeared to be inactive.The morphology of platelet thrombi induced by an electric stimulus is shown. The probability of a primary role of erythrocytes in the formation of this type of thrombi is discussed.

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