scholarly journals Effects of Spontaneous Bilayer Curvature on Influenza Virus–mediated Fusion Pores

1998 ◽  
Vol 112 (4) ◽  
pp. 409-422 ◽  
Author(s):  
Vladimir I. Razinkov ◽  
Grigory B. Melikyan ◽  
Richard M. Epand ◽  
Raquel F. Epand ◽  
Fredric S. Cohen
Keyword(s):  
Influenza Virus ◽  
Negative Curvature ◽  
Hexagonal Phase ◽  
Three Dimensional ◽  
Bilayer Membrane ◽  
Spontaneous Curvature ◽  
Dependent Manner ◽  
Small Pore ◽  
In Trans ◽  
Fusion Pores

Cells expressing the hemagglutinin protein of influenza virus were fused to planar bilayer membranes containing the fluorescent lipid probes octadecylrhodamine (R18) or indocarbocyanine (DiI) to investigate whether spontaneous curvature of each monolayer of a target membrane affects the growth of fusion pores. R18 and DiI lowered the transition temperatures for formation of an inverted hexagonal phase, indicating that these probes facilitate the formation of negative curvature structures. The probes are known to translocate from one monolayer of a bilayer membrane to the other in a voltage-dependent manner. The spontaneous curvature of the cis monolayer (facing the cells) or the trans monolayer could therefore be made more negative through control of the polarity of voltage across the planar membrane. Electrical admittance measurements showed that the open times of flickering fusion pores were shorter when probes were in trans monolayers and longer when in cis monolayers compared with times when probe was symmetrically distributed. Open times were the same for probe symmetrically distributed as when probes were not present. Thus, open times were a function of the asymmetry of the spontaneous curvature between the trans and cis monolayers. Enriching the cis monolayer with a negative curvature probe reduced the probability that a small pore would fully enlarge, whereas enriching the trans monolayer promoted enlargement. Lysophosphatidylcholine has positive spontaneous curvature and does not translocate. When lysophosphatidylcholine was placed in trans leaflets of planar membranes, closing of fusion pores was rare. The effects of the negative and positive spontaneous curvature probes do not support the hypothesis that a flickering pore closes from an open state within a hemifusion diaphragm (essentially a “flat” structure). Rather, such effects support the hypothesis that the membrane surrounding the open pore forms a three-dimensional hourglass shape from which the pore flickers shut.

scholarly journals Inner but Not Outer Membrane Leaflets Control the Transition from Glycosylphosphatidylinositol-anchored Influenza Hemagglutinin-induced Hemifusion to Full Fusion

1997 ◽  
Vol 136 (5) ◽  
pp. 995-1005 ◽  
Author(s):  
Grigory B. Melikyan ◽  
Sofya A. Brener ◽  
Dong C. Ok ◽  
Fredric S. Cohen
Keyword(s):  
Outer Membrane ◽  
Negative Curvature ◽  
Pore Formation ◽  
Transmembrane Domain ◽  
Positive Curvature ◽  
Fusion Pore ◽  
Spontaneous Curvature ◽  
Wild Type ◽  
Influenza Hemagglutinin ◽  
Fusion Pores

Cells that express wild-type influenza hemagglutinin (HA) fully fuse to RBCs, while cells that express the HA-ectodomain anchored to membranes by glycosylphosphatidylinositol, rather than by a transmembrane domain, only hemifuse to RBCs. Amphipaths were inserted into inner and outer membrane leaflets to determine the contribution of each leaflet in the transition from hemifusion to fusion. When inserted into outer leaflets, amphipaths did not promote the transition, independent of whether the agent induces monolayers to bend outward (conferring positive spontaneous monolayer curvature) or inward (negative curvature). In contrast, when incorporated into inner leaflets, positive curvature agents led to full fusion. This suggests that fusion is completed when a lipidic fusion pore with net positive curvature is formed by the inner leaflets that compose a hemifusion diaphragm. Suboptimal fusion conditions were established for RBCs bound to cells expressing wild-type HA so that lipid but not aqueous dye spread was observed. While this is the same pattern of dye spread as in stable hemifusion, for this “stunted” fusion, lower concentrations of amphipaths in inner leaflets were required to promote transfer of aqueous dyes. Also, these amphipaths induced larger pores for stunted fusion than they generated within a stable hemifusion diaphragm. Therefore, spontaneous curvature of inner leaflets can affect formation and enlargement of fusion pores induced by HA. We propose that after the HA-ectodomain induces hemifusion, the transmembrane domain causes pore formation by conferring positive spontaneous curvature to leaflets of the hemifusion diaphragm.

scholarly journals Prostacyclin as a Negative Regulator of Angiogenesis in the Neurovasculature

2021 ◽  
Author(s):  
Tasha R Womack ◽  
Jiabing Li ◽  
Pavel A Govyadinov ◽  
David Mayerich ◽  
Jason L Eriksen
Keyword(s):  
Three Dimensional ◽  
Tube Formation ◽  
Negative Regulator ◽  
Dependent Manner ◽  
Ip Receptor ◽  
Subunit Expression ◽  
Gs Protein ◽  
In Trans ◽  
Camp Levels ◽  
Dose Dependent

AbstractIn this study, multiple measures of angiogenic processes were assessed in murine brain endothelial (bEnd.3) cells after exposure to the stable prostacyclin analog, iloprost. Additionally, changes in the γ-secretase enzyme were evaluated after activation of prostacyclin signaling using PGI2 overexpressing mouse brain tissue and immunohistology studies in bEnd.3 cells. A three-dimensional assay of tube formation revealed that iloprost inhibits normal formation by significantly reduced tube lengths and vessel mesh area. The iloprost-mediated inhibition of tube-like structures was ameliorated by a specific IP-receptor antagonist, CAY10449. Reductions in wound healing were observed with iloprost application in a dose-dependent manner and this effect was reversed using CAY10449. Iloprost did not exhibit anti-proliferative effects in the bEnd.3 cells. When subjected to a Transwell assay to evaluate changes in trans-epithelial electrical resistance (TEER), bEnd.3 cells displayed reduced TEER values in the presence of iloprost an effect that lasted over prolonged periods (24 hours). Again, CAY10449 was able to reverse iloprost-mediated reductions in TEER value. Surprisingly, the adenylyl cyclase activator, forskolin, produced higher TEER values in the bEnd.3 cells over the same time. The TEER results suggest that iloprost may not activating the Gs protein of the IP receptor to increase cAMP levels given by the opposing results seen with iloprost and forskolin. In terms of γ-secretase expression, PGI2 overexpression in mice increased the expression of the APH-1α subunit in the hippocampus and cortex. In bEnd.3 cells, iloprost application slightly increased APH-1α subunit expression measured by western blot and interrupted the colocalization of Presenilin 1 and APH-1α subunits using immunohistochemistry. The results suggest that prostacyclin signaling within bEnd.3 cells is anti-angiogenic and further downstream events have effects on the expression and most likely the activity of the Aβ cleaving enzyme, γ-secretase.

scholarly journals A specific phase of transcranial alternating current stimulation at the β frequency boosts repetitive paired-pulse TMS-induced plasticity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hisato Nakazono ◽  
Katsuya Ogata ◽  
Akinori Takeda ◽  
Emi Yamada ◽  
Shinichiro Oka ◽  
...  
Keyword(s):  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Single Pulse ◽  
Alternating Current ◽  
Dependent Manner ◽  
Synaptic Efficacy ◽  
Paired Pulse ◽  
Transcranial Alternating Current Stimulation ◽  
In Trans ◽  
Specific Phase

AbstractTranscranial alternating current stimulation (tACS) at 20 Hz (β) has been shown to modulate motor evoked potentials (MEPs) when paired with transcranial magnetic stimulation (TMS) in a phase-dependent manner. Repetitive paired-pulse TMS (rPPS) with I-wave periodicity (1.5 ms) induced short-lived facilitation of MEPs. We hypothesized that tACS would modulate the facilitatory effects of rPPS in a frequency- and phase-dependent manner. To test our hypothesis, we investigated the effects of combined tACS and rPPS. We applied rPPS in combination with peak or trough phase tACS at 10 Hz (α) or β, or sham tACS (rPPS alone). The facilitatory effects of rPPS in the sham condition were temporary and variable among participants. In the β tACS peak condition, significant increases in single-pulse MEPs persisted for over 30 min after the stimulation, and this effect was stable across participants. In contrast, β tACS in the trough condition did not modulate MEPs. Further, α tACS parameters did not affect single-pulse MEPs after the intervention. These results suggest that a rPPS-induced increase in trans-synaptic efficacy could be strengthened depending on the β tACS phase, and that this technique could produce long-lasting plasticity with respect to cortical excitability.

scholarly journals Application of subject-specific adaptive mechanical loading for bone healing in a mouse tail vertebral defect

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Angad Malhotra ◽  
Matthias Walle ◽  
Graeme R. Paul ◽  
Gisela A. Kuhn ◽  
Ralph Müller
Keyword(s):  
Mechanical Loading ◽  
Bone Defect ◽  
Bone Healing ◽  
Three Dimensional ◽  
Patient Specific ◽  
Dependent Manner ◽  
Micro Computed Tomography ◽  
Computed Tomography Images ◽  
Bone Defect Healing ◽  
Subject Specific

AbstractMethods to repair bone defects arising from trauma, resection, or disease, continue to be sought after. Cyclic mechanical loading is well established to influence bone (re)modelling activity, in which bone formation and resorption are correlated to micro-scale strain. Based on this, the application of mechanical stimulation across a bone defect could improve healing. However, if ignoring the mechanical integrity of defected bone, loading regimes have a high potential to either cause damage or be ineffective. This study explores real-time finite element (rtFE) methods that use three-dimensional structural analyses from micro-computed tomography images to estimate effective peak cyclic loads in a subject-specific and time-dependent manner. It demonstrates the concept in a cyclically loaded mouse caudal vertebral bone defect model. Using rtFE analysis combined with adaptive mechanical loading, mouse bone healing was significantly improved over non-loaded controls, with no incidence of vertebral fractures. Such rtFE-driven adaptive loading regimes demonstrated here could be relevant to clinical bone defect healing scenarios, where mechanical loading can become patient-specific and more efficacious. This is achieved by accounting for initial bone defect conditions and spatio-temporal healing, both being factors that are always unique to the patient.

scholarly journals Dendritic Fibroblasts in Three-dimensional Collagen Matrices

2003 ◽  
Vol 14 (2) ◽  
pp. 384-395 ◽  
Author(s):  
Frederick Grinnell ◽  
Chin-Han Ho ◽  
Elisa Tamariz ◽  
David J. Lee ◽  
Gabriella Skuta
Keyword(s):  
Dimensional Space ◽  
Human Fibroblasts ◽  
Three Dimensional ◽  
Rho Kinase ◽  
Matrix Remodeling ◽  
Dependent Manner ◽  
Collagen Matrices ◽  
Form And Function ◽  
Metabolic Coupling ◽  
Dendritic Network

Cell motility determines form and function of multicellular organisms. Most studies on fibroblast motility have been carried out using cells on the surfaces of culture dishes. In situ, however, the environment for fibroblasts is the three-dimensional extracellular matrix. In the current research, we studied the morphology and motility of human fibroblasts embedded in floating collagen matrices at a cell density below that required for global matrix remodeling (i.e., contraction). Under these conditions, cells were observed to project and retract a dendritic network of extensions. These extensions contained microtubule cores with actin concentrated at the tips resembling growth cones. Platelet-derived growth factor promoted formation of the network; lysophosphatidic acid stimulated its retraction in a Rho and Rho kinase-dependent manner. The dendritic network also supported metabolic coupling between cells. We suggest that the dendritic network provides a mechanism by which fibroblasts explore and become interconnected to each other in three-dimensional space.

scholarly journals Role of the HSP70 Co-Chaperone SIL1 in Health and Disease

2021 ◽  
Vol 22 (4) ◽  
pp. 1564
Author(s):  
Viraj P. Ichhaporia ◽  
Linda M. Hendershot
Keyword(s):  
Molecular Mechanisms ◽  
Three Dimensional ◽  
Dependent Manner ◽  
Nucleotide Exchange ◽  
Multisystem Disorder ◽  
Nucleotide Exchange Factors ◽  
Precise Understanding ◽  
Health And Disease ◽  
Client Proteins ◽  
Er Homeostasis

Cell surface and secreted proteins provide essential functions for multicellular life. They enter the endoplasmic reticulum (ER) lumen co-translationally, where they mature and fold into their complex three-dimensional structures. The ER is populated with a host of molecular chaperones, associated co-factors, and enzymes that assist and stabilize folded states. Together, they ensure that nascent proteins mature properly or, if this process fails, target them for degradation. BiP, the ER HSP70 chaperone, interacts with unfolded client proteins in a nucleotide-dependent manner, which is tightly regulated by eight DnaJ-type proteins and two nucleotide exchange factors (NEFs), SIL1 and GRP170. Loss of SIL1′s function is the leading cause of Marinesco-Sjögren syndrome (MSS), an autosomal recessive, multisystem disorder. The development of animal models has provided insights into SIL1′s functions and MSS-associated pathologies. This review provides an in-depth update on the current understanding of the molecular mechanisms underlying SIL1′s NEF activity and its role in maintaining ER homeostasis and normal physiology. A precise understanding of the underlying molecular mechanisms associated with the loss of SIL1 may allow for the development of new pharmacological approaches to treat MSS.

Enhanced growth and myogenic differentiation of spheroid-derived C2C12 cells

2021 ◽  
Author(s):  
Guang-Zhen Jin
Keyword(s):  
Myogenic Differentiation ◽  
Three Dimensional ◽  
3D Culture ◽  
Stem Cell Differentiation ◽  
Culture Conditions ◽  
C2c12 Cells ◽  
Dependent Manner ◽  
Physical Force ◽  
Myod Gene ◽  
2D And 3D

Abstract Among many factors of controlling stem cell differentiation, the key transcription factor upregulation via physical force is a good strategy on the lineage-specific differentiation of stem cells. The study aimed to compare growth and myogenic potentials between the parental cells (PCs) and the 1-day-old C2C12 spheroid-derived cells (SDCs) in two-dimensional (2D) and three-dimensional (3D) culture conditions through examination of the cell proliferation and the expression of myogenic genes. The data showed that 1-day-old spheroids had more intense expression of MyoD gene with respect to the PCs. The proliferation of the SDCs significantly higher than the PCs in a time dependent manner. The SDCs had also significantly higher myogenic potential than the PCs in 2D and 3D culture conditions. The results suggest that MyoD gene upregulation through cell-cell contacts is the good approach for preparation of seed cells in muscle tissue engineering.

Broadly-neutralizing antibodies that bind to the influenza hemagglutinin stalk domain enhance the effectiveness of neuraminidase inhibitors via Fc-mediated effector functions

2021 ◽  
Author(s):  
Ali Zhang ◽  
Hanu Chaudhari ◽  
Yonathan Agung ◽  
Michael D'Agostino ◽  
Jann Ang ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Neutralizing Antibodies ◽  
Influenza Virus Infection ◽  
Dependent Manner ◽  
Neuraminidase Inhibitors ◽  
Immune Effector ◽  
Effector Cells ◽  
Individual Level ◽  
Influenza Hemagglutinin ◽  
Stalk Domain

The conserved hemagglutinin stalk domain is an attractive target for broadly effective antibody-based therapeutics and next generation universal influenza vaccines. Protection provided by hemagglutinin stalk binding antibodies is principally mediated through activation of immune effector cells. Titers of stalk-binding antibodies are highly variable on an individual level, and tend to increase with age as a result of increasing exposures to influenza virus. In our study, we show that stalk-binding antibodies cooperate with neuraminidase inhibitors to protect against influenza virus infection in an Fc-dependent manner. These data suggest that the effectiveness of neuraminidase inhibitors is likely influenced by an individual's titers of stalk-binding antibodies, and that neuraminidase inhibitors may enhance the effectiveness of future stalk-binding monoclonal antibody-based treatments.

Three-Dimensional Tracking of Rab5- and Rab7-Associated Infection Process of Influenza Virus

Small ◽  
2014 ◽  
Vol 10 (22) ◽  
pp. 4746-4753 ◽  
Author(s):  
Shu-Lin Liu ◽  
Qiu-Mei Wu ◽  
Li-Juan Zhang ◽  
Zhi-Gang Wang ◽  
En-Ze Sun ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Three Dimensional ◽  
Infection Process
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