The composite and versatile structure of the cytoskeleton confers complex mechanical properties on cells. Actin filaments sustain the cell membrane and their dynamics insure cell shape changes. For example, the lamellipodium moves by actin polymerization, a mechanism that has been studied using simplified experimental systems. Much less is known about the actin cortex, a shell-like structure un...

Multi-color fluorescence imaging experiments of wave forming Dictyostelium cells have revealed that actin waves separate two domains of the cell cortex that differ in their actin structure and phosphoinositide composition. We propose a bistable model of actin dynamics to account for these experimental observation. The model is based on the simplifying assumption that the actin cytoskeleton is c...

Does cytosolic pressure facilitate f-actin polymerization to push the leading edge of a cell forward during self-propelled motion? AFM force-distance (f-d) curves obtained from lamellipodia of live cells often exhibit a signal from which the tension, bending modulus, elastic modulus and thickness in the membrane-cortex complex can be estimated close to the contact point. These measurements perm...

Within the confines of tissues, cancer cells can use blebs to migrate. Eps8 is an actin bundling and capping protein whose capping activity is inhibited by Erk, a key MAP kinase that is activated by oncogenic signaling. We tested the hypothesis that Eps8 acts as an Erk effector to modulate actin cortex mechanics and thereby mediate bleb-based migration of cancer cells. Cells confined in a non-a...

The state of actin in the isolated cortex of the unfertilized sea urchin egg can be controlled by experimentally manipulating the pH of the isolation medium. Cortices isolated at the pH of the unfertilized egg (6.5--6.7) do not contain filamentous actin, while those isolated at the pH of the fertilized egg (7.3--7.5) develop large numbers of microvilli which contain bundles of actin filaments. ...