Theoretical analysis of shape transformation of V-79 cells after treatment with cytochalasin B

Coupling of nematic in-plane orientational ordering and equilibrium shapes of closed flexible nematic shells

The impact of the intrinsic curvature of in-plane orientationally ordered curved flexible nematic molecules attached to closed 3D flexible shells was studied numerically. A Helfrich-Landau-de Gennes-type mesoscopic approach was adopted where the flexible shell's curvature field and in-plane nematic field are coupled and concomitantly determined in the process of free energy minimisation. We demonstrate that this coupling has the potential to generate a rich diversity of qualitatively new shapes of closed 3D nematic shells and the corresponding specific in-plane orientational ordering textures, which strongly depend on the shell's volume-to-surface area ratio, so far not predicted in mesoscopic-type numerical studies of 3D shapes of closed flexible nematic shells.

On the role of external force of actin filaments in the formation of tubular protrusions of closed membrane shapes with anisotropic membrane components

Biological membranes are composed of different components and there is no a priori reason to assume that all components are isotropic. It was previously shown that the anisotropic properties of membrane components may explain the stability of membrane tubular protrusions even without the application of external force. Our theoretical study focuses on the role of anisotropic membrane components in the stability of membrane tubular structures generated or stabilized by actin filaments. We show that the growth of the actin cytoskeleton inside the vesicle can induce the partial lateral segregation of different membrane components. The entropy of mixing of membrane components hinders the total lateral segregation of the anisotropic and isotropic membrane components. Self-assembled aggregates formed by anisotropic membrane components facilitate the growth of long membrane tubular protrusions. Protrusive force generated by actin filaments favors strong segregation of membrane components by diminishing the opposing effect of mixing entropy.

Subcellular characterization of glucose uptake in coronary endothelial cells

Despite all the evidence linking glucose toxicity to an increased risk of cardiovascular diseases, very little is known about the regulation of glucose uptake in endothelial cells. We have previously reported an asymmetric distribution of the GLUTs (1-5) and SGLT-1 in en face preparations of rat coronary artery endothelia [Gaudreault N., Scriven D.R., Moore E.D., 2004. Characterisation of glucose transporters in the intact coronary artery endothelium in rats: GLUT-2 upregulated by long-term hyperglycaemia. Diabetologia 47(12),2081-2092]. We assessed this time, through immunocytochemistry and wide field fluorescence microscopy coupled to deconvolution, the presence and subcellular distribution of glucose transporters in cultures of human coronary artery endothelial cells (HCAECs). HCAECs express GLUT-1 to 5 and SGLT-1, but their subcellular distribution lacks the luminal/abluminal asymmetry and the proximity to cell-to-cell junctions observed in intact endothelium. To determine the impact of the transporters' distribution on intracellular glucose accumulation, a fluorescent glucose analog (2-NBDG) was used in conjunction with confocal microscopy to monitor uptake in individual cells; the arteries were mounted in an arteriograph chamber with physiological flow rates. The uptake in both preparations was inhibited by cytochalasin-B and d-glucose and stimulated by insulin, but the distribution of the incorporated 2-NBDG mirrored that of the transporters. In HCAEC it was distributed throughout the cell and in the intact arterial endothelium it was restricted to the narrow cytosolic volume adjacent to the cell-to-cell junctions. We suggest that the latter subcellular organization and compartmentalization may facilitate transendothelial transport of glucose in intact coronary artery.