A New Dimension in Retrograde Flow: Centripetal Movement of Engulfed Particles

Abstract

Centripetal motion of surface-adherent particles is a classic experimental system for studying surface dynamics on a eukaryotic cell. To investigate bead migration over the entire cell surface, we have developed an experimental assay using multinuclear giant fibroblasts, which provide expanded length scales and an unambiguous frame of reference. Beads coated by adhesion ligands concanavalin A or fibronectin are placed in specific locations on the cell using optical tweezers, and their subsequent motion is tracked over time. The adhesion, as well as velocity and directionality of their movement, expose distinct regions of the cytoplasm and membrane. Beads placed on the peripheral lamella initiate centripetal motion, whereas beads placed on the central part of the cell attach to a stationary cortex and do not move. Careful examination by complementary three-dimensional methods shows that the motion of a bead placed on the cell periphery takes place after engulfment into the cytoplasm, whereas stationary beads, placed near the cell center, are not engulfed. These results demonstrate that centripetal motion of adhering particles may occur inside as well as outside the cell. Inhibition of actomyosin activity is used to explore requirements for engulfment and aspects of the bead movement. Centripetal movement of adherent particles seems to depend on mechanisms distinct from those driving overall cell contractility.

A New Approach to Follow a Single Extracellular Vesicle—Cell Interaction using Optical Tweezers

“…Interestingly, the velocity of MV movement on microglia is in the same range of that reported for adenoviral particles, which bind to cell surface receptors (32). It also resembles the speed of retrograde actin flow (33), which regulates the lateral diffusion of transmembrane proteins linked to actin (34). Given that both viruses and EVs are recognized on cells by surface receptors (35,36, and this study), the possibility arises that the motion of EVs outside microglia may be caused by the lateral diffusion of EV receptors, as previously suggested (37).…”

Actin‐based centripetal flow: Phosphatase inhibition by calyculin‐A alters flow pattern, actin organization, and actomyosin distribution

“…In addition, actomyosin contraction during cytokinesis in control echinoderm embryos has been demonstrated to correlate with MRLC phosphorylation [Shuster and Burgess, 1999]. Past research on centripetal/retrograde flow in other cell types has tended to concentrate on the inhibition as opposed to the stimulation of actomyosin contraction [Lin et al, 1996;Waterman-Storer and Salmon, 1997;Caspi et al, 2001;Suter and Forscher, 2001]. Therefore, we argue that the present study represents a relatively novel approach.…”

Cellular Dynamics of EGF Receptor–Targeted Synthetic Viruses

“…21 The velocity of actin-mediated motion observed in our study is well in accordance with velocities reported for endocytosed latex beads that showed an actin-mediated retrograde flow with an average velocity of v = 0.016 µm/s (ref. 22) for gold particles bound to cell surface glycoproteins. 21 The three-phase uptake characteristics of polyplexes resemble the three-stage internalization process described for influenza viruses.…”