scholarly journals Regulation of the membrane wrapping transition of a cylindrical target by cytoskeleton adhesion

2014 ◽  
Vol 11 (100) ◽  
pp. 20140769 ◽  
Author(s):  
Seyed Mahmoud Hashemi ◽  
Pierre Sens ◽  
Farshid Mohammad-Rafiee
Keyword(s):  
Cell Membrane ◽  
Elastic Deformation ◽  
Actin Polymerization ◽  
Force Balance ◽  
Bending Rigidity ◽  
External Objects ◽  
Cylindrical Target ◽  
Membrane Bending ◽  
Target Binding ◽  
Active Force Generation

The adsorption of external objects to the cell membrane often triggers cellular responses involving large deformations. In phagocytosis, upon contact with the target, the cell creates large extensions that wrap around the target and ultimately lead to its engulfment. Although active force generation, in particular by actin polymerization, is required for completion of this process, the elastic deformation of the cell membrane upon adhesion to an external object might play an important part in its initiation. In this paper, the elastic deformation of a bilayer owing to the binding of a cylindrical object is studied, taking into account the membrane bending rigidity and the surface tension, the membrane adhesion to both the external target and inner cytoskeleton. The problem is studied within the framework of the Helfrich–Hamiltonian and using force balance relations and the proper boundary conditions that are related to the adhesion energy coefficients. It is shown that membrane wrapping around the target may be a continuous or abrupt transition upon increasing the target binding energy, depending on the value of the parameter. The degree of wrapping and the shape of the membrane in the vicinity of the object are computed numerically, and analytical expressions are given for the boundaries separating the different wrapping regimes in the parameter space.

scholarly journals Actin Polymerization in Macrophages in Response to Oxidized LDL and Apoptotic Cells: Role of 12/15-Lipoxygenase and Phosphoinositide 3-Kinase

2003 ◽  
Vol 14 (10) ◽  
pp. 4196-4206 ◽  
Author(s):  
Yury I. Miller ◽  
Dorothy S. Worrall ◽  
Colin D. Funk ◽  
James R. Feramisco ◽  
Joseph L. Witztum
Keyword(s):  
Cell Membrane ◽  
Actin Polymerization ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Specific Inhibitor ◽  
Density Lipoprotein ◽  
Oxidation Products ◽  
Apoptotic Cells ◽  
Lipid Oxidation Products ◽  
Phosphoinositide 3 Kinase

Formation of filamentous F-actin drives many cellular processes, including phagocytosis and cell spreading. We have recently reported that mouse macrophage 12/15-lipoxygenase (12/15-LO) activity promotes F-actin formation in filopodia during phagocytosis of apoptotic cells. Oxidized low-density lipoprotein (OxLDL) also stimulates robust F-actin formation and spreading of macrophages. However, unlike apoptotic cells, OxLDL did not cause specific translocation of 12/15-LO to the cell membrane, neither in macrophages nor in GFP-15LO–transfected COS-7 cells. Moreover, inhibition of 12/15-LO activity in macrophages by a specific inhibitor or by 12/15-LO gene disruption did not affect OxLDL-induced actin polymerization. Among LDL modifications modeling OxLDL, LDL modified by incubation with 15LO-overexpressing fibroblasts was as active in eliciting F-actin response as was OxLDL. This LDL modification is well known to produce minimally modified LDL (mmLDL), which is bioactive and carries lipid oxidation products similar to those produced by 12/15-LO catalysis. MmLDL activated phosphoinositide 3-kinase (PI3K), and PI3K inhibitors abolished mmLDL-induced macrophage spreading. We hypothesize that OxLDL and mmLDL may contribute oxidized lipids to the macrophage cell membrane and thereby mimic intracellular 12/15-LO activity, which leads to uncontrolled actin polymerization and dramatic cytoskeletal changes in macrophages.

scholarly journals Impact of Sterol Tilt on Membrane Bending Rigidity in Cholesterol and 7DHC-Containing DMPC Membrane

2012 ◽  
Vol 102 (3) ◽  
pp. 413a
Author(s):  
George Khelashvili ◽  
Michael Rappolt ◽  
See-Wing Chiu ◽  
Georg Pabst ◽  
Daniel Harries
Keyword(s):  
Bending Rigidity ◽  
Membrane Bending ◽  
Dmpc Membrane

Finite Elastic Deformation of an Annular Rotating Disk

1976 ◽  
Vol 98 (4) ◽  
pp. 375-379 ◽  
Author(s):  
J. B. Haddow ◽  
M. G. Faulkner
Keyword(s):  
Elastic Deformation ◽  
Strain Energy ◽  
Equations Of Motion ◽  
Strain Energy Function ◽  
Rotating Disk ◽  
Force Balance ◽  
Annular Disk ◽  
Incompressible Materials ◽  
Plane Stress Problem ◽  
Governing Differential Equation

An accurate approximate method for the solution of the generalized plane stress problem of finite elastic deformation of a rotating annular disk is given. The method is applicable to both compressible and incompressible materials. Use of the nonlinear governing differential equation is avoided by considering the disk to be an aggregate of discrete coaxial rings, equations of motion, force balance and compatibility relations being formulated for the rings. Results are given for neo-Hookean disks and disks of a compressible material which has a strain energy function proposed by Blatz and Ko [7].

Spectrin–ankyrin interaction mechanics: A key force balance factor in the red blood cell membrane skeleton

2015 ◽  
Vol 200-201 ◽  
pp. 1-8 ◽  
Author(s):  
Masakazu Saito ◽  
Takahiro Watanabe-Nakayama ◽  
Shinichi Machida ◽  
Toshiya Osada ◽  
Rehana Afrin ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Membrane Skeleton ◽  
Force Balance ◽  
Red Blood Cell Membrane ◽  
Balance Factor

scholarly journals Type-I myosins promote actin polymerization to drive membrane bending in endocytosis

2018 ◽  
Author(s):  
Hetty E Manenschijn ◽  
Andrea Picco ◽  
Markus Mund ◽  
Jonas Ries ◽  
Marko Kaksonen
Keyword(s):  
Live Cell Imaging ◽  
Actin Polymerization ◽  
Cell Imaging ◽  
Turgor Pressure ◽  
Type I ◽  
Actin Network ◽  
Actin Nucleation ◽  
Genetic Perturbations ◽  
Membrane Bending ◽  
Dose Dependent

Clathrin-mediated endocytosis in budding yeast requires the formation of a dynamic actin network that produces the force to invaginate the plasma membrane against the intracellular turgor pressure. The type-I myosins Myo3 and Myo5 are important for endocytic membrane reshaping, but mechanistic details of their function remain scarce. Here, we studied the function of Myo3 and Myo5 during endocytosis using quantitative live-cell imaging and genetic perturbations. We show that the type-I myosins promote, in a dose-dependent way, the growth and expansion of the actin network, which controls the speed of membrane and coat internalization. We found that this myosin-activity is independent of the actin nucleation promoting activity of myosins, and cannot be compensated for by increasing actin nucleation. Our results suggest a new mechanism for type-I myosins to produce force by promoting actin filament polymerization.

scholarly journals Membrane stiffness is a key determinant of E coli MscS channel mechanosensitivity

2019 ◽  
Author(s):  
Feng Xue ◽  
Charles D. Cox ◽  
Navid Bavi ◽  
Paul R Rohde ◽  
Yoshitaka Nakayama ◽  
...  
Keyword(s):  
Response Curve ◽  
Membrane Lipids ◽  
Bending Rigidity ◽  
Rightward Shift ◽  
E Coli ◽  
Tension Response ◽  
Global Properties ◽  
Membrane Stiffness ◽  
Membrane Bending ◽  
Branched Chain

AbstractProkaryotic mechanosensitive (MS) channels have an intimate relationship with membrane lipids. Membrane lipids may influence channel activity by directly interacting with bacterial MS channels or by influencing the global properties of the membrane such as area stretch and bending moduli. Previous work has implicated membrane stiffness as a key determinant of the mechanosensitivity of E. coli (Ec)MscS. Here we systematically tested this hypothesis using patch fluorometry of azolectin liposomes doped with lipids of increasing area stretch moduli. Increasing DOPE content of azolectin liposomes causes a rightward shift in the tension response curve of EcMscS. These rightward shifts are further magnified by the addition of stiffer forms of PE such as the branched chain lipid DPhPE and the fully saturated lipid DSPE. Furthermore, a comparison of the branched chain lipid DPhPC to the stiffer DPhPE showed a rightward shift in the tension response curve in the presence of the stiffer DPhPE. We show that these changes are not due to changes in membrane bending rigidity as the tension threshold of EcMscS in membranes doped with PC18:1 and PC18:3 are the same, despite a two-fold difference in their bending rigidity. We also show that after prolonged pressure application sudden removal of force in softer membranes causes a rebound reactivation of EcMscS and we discuss the relevance of this phenomenon to bacterial osmoregulation. Collectively, our data demonstrate that membrane stiffness is a key determinant of the mechanosensitivity of EcMscS.

Myosin II-dependent cylindrical protrusions induced by quinine inDictyostelium: antagonizing effects of actin polymerization at the leading edge

2001 ◽  
Vol 114 (11) ◽  
pp. 2155-2165
Author(s):  
Kunito Yoshida ◽  
Kei Inouye
Keyword(s):  
Cell Membrane ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Cell Movement ◽  
Leading Edge ◽  
Contractile Vacuole ◽  
Cell Periphery ◽  
Slowing Down ◽  
On Line ◽  
Cylindrical Protrusion

We found that amoeboid cells of Dictyostelium are induced by a millimolar concentration of quinine to form a rapidly elongating, cylindrical protrusion, which often led to sustained locomotion of the cells. Formation of the protrusion was initiated by fusion of a contractile vacuole with the cell membrane. During protrusion extension, a patch of the contractile vacuole membrane stayed undiffused on the leading edge of the protrusion for over 30 seconds. Protrusion formation was not inhibited by high osmolarity of the external medium (at least up to 400 mosM). By contrast, mutant cells lacking myosin II (mhc− cells) failed to extend protrusions upon exposure to quinine. When GFP-myosin-expressing cells were exposed to quinine, GFP-myosin was accumulated in the cell periphery forming a layer under the cell membrane, but a newly formed protrusion was initially devoid of a GFP-myosin layer, which gradually formed and extended from the base of the protrusion. F-actin was absent in the leading front of the protrusion during the period of its rapid elongation, and the formation of a layer of F-actin in the front was closely correlated with its slowing-down or retraction. Periodical or continuous detachment of the F-actin layer from the apical membrane of the protrusion, accompanied by a transient increase in the elongation speed at the site of detachment, was observed in some of the protrusions. The detached F-actin layers, which formed a spiral layer of F-actin in the case of continuous detachment, moved in the opposite direction of protrusion elongation. In the presence of both cytochalasin A and quinine, the protrusions formed were not cylindrical but spherical, which swallowed up the entire cellular contents. The estimated bulk flux into the expanding spherical protrusions of such cells was four-times higher than the flux into the elongating cylindrical protrusions of the cells treated with quinine alone. These results indicate that the force responsible for the quinine-induced protrusion is mainly due to contraction of the cell body, which requires normal myosin II functions, while actin polymerization is important in restricting the direction of its expansion. We will discuss the possible significance of tail contraction in cell movement in the multicellular phase of Dictyostelium development, where cell locomotion similar to that induced by quinine is often observed without quinine treatment, and in protrusion elongation in general.Movies available on-line

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