To answer these questions, we utilize lamellipodial fragments from fish epithelial keratocytes which lack a cell body but retain the ability to crawl

To answer these questions, we utilize lamellipodial fragments from fish epithelial keratocytes which lack a cell body but retain the ability to crawl. by where the actin network has disassembled enough for membrane tension to crush it and haul it forward. This model allows us to directly relate membrane tension with actin assembly and disassembly dynamics and elucidate the role of the cell membrane as a global mechanical regulator which coordinates protrusion and retraction. Keywords:cell motility, keratocyte fragments Understanding the large-scale coordination of molecular processes into coherent behavior at the cellular level is one of the central difficulties in cell biology. Actin-based motility entails numerous molecular players with complex interactions (1) that span a wide-range of scales from your molecular level to the cellular one. Despite substantial progress in characterizing the molecular details involved (2), we still do not understand the amazing self-organization of these molecular components into a moving cell. The complex interplay between biochemical reactions and biophysical causes plays a central role in this self-organization. In particular, the mechanical opinions between the cell membrane and the dynamic actin network has been shown to have a substantial effect on cell protrusion (3,4), and a significant role in coordinating protrusion over cellular scales (5,6). However, quantitative understanding of the coupling between the cell membrane Gamithromycin and the motility machinery is still lacking; it is unknown what determines membrane tension and how membrane tension is related to the protrusion and retraction dynamics. Elucidating this dynamic interplay is essential for understanding how overall cell morphology and movement emerge from your underlying molecular processes. Fish epithelial keratocytes are widely used for studying the dynamics of the motility process (5,710); they are one of the fastest moving animal cells with common speeds of up to 1 m/s, yet their motion is extremely persistent with hardly any switch in cell shape, velocity, or direction over many minutes. Keratocytes, as well as other motile cell types (11), can spontaneously detach cytoplasmic fragments which move with speed and persistence similar to whole-cells (1214). These lamellipodial fragments, which lack nuclei, microtubules, and most organelles, are likely the simplest natural model system for studying actin-based cell motility. As such, this system has been used Mouse monoclonal to His tag 6X to gain insight into the minimal requirements for establishing polarity in motile cells (12,13). Here we utilize this simplified model system to Gamithromycin study how the interplay between actin dynamics and the plasma membrane lead to shape and movement of the lamellipodium as a whole. The lack of a cell body in fragments facilitates measurements of geometry and movement of the rear boundary, allowing us to focus on the important question of how retraction at the rear is coordinated with protrusion at the front. We combine experimental characterization and modeling and propose a self-consistent biophysical model of the lamellipodial motility module. We show that membrane tension mechanically couples edge dynamics along the cell boundary; at the rear, Gamithromycin membrane tension provides the force needed for retraction Gamithromycin and actin network disassembly, whereas a force balance between actin polymerization and membrane tension shapes the leading edge (5). Overall, our model explains in a quantitative and self-consistent manner how global shape and speed of the lamellipodium emerge from the underlying dynamics of the actin treadmill within an inextensible membrane bag, and provides values for membrane tension as an output of the model rather than incorporating tension as an input parameter..