What are filopodia? Filopodia (singular filopodium) are thin membrane protrusions that act as antennae for a cell to probe the surrounding environment [1][2][3]. Nonprotruding filopodia are mechanistically related to microspikes [4]. Filopodia are commonly found embedded within, or protruding from the lamelliopodium at the [...]

What is the first step in filopodium formation? Actin nucleation initiates filopodium formation The first step in the formation of a filopodium is the nucleation of actin filaments from G-actin monomers. This is facilitated by various proteins known as nucleators, and may occur via [...]

How does cross-linking of actin filaments aid in filopodia extension? Once nucleation has taken place, actin filaments begin to extend. This process is primarily facilitated by members of the formin family of proteins, however numerous other proteins also play important roles. In the ‘convergent [...]

What are invadopodia? Invadopodia are actin-rich structures that are present at the basal surfaces of cells that are capable of crossing extracellular barriers, such as cancer cells. The primary function of invadopodia appears to be the focal degradation of the extracellular matrix (ECM) through [...]

What is the role of the lamellipodia in mechanosensing and cell motility? During cell migration, and in the absence of filopodia, lamellipodia detect the stiffness of the surrounding ECM in a process called rigidity sensing. Several models have been proposed that describe this process. [...]

What steps are involved in Lamellipodia assembly? The lamellipodia is a distinct region of the cell that facilitates cell motility and various mechanosensing mechanisms. Lamellipodium assembly can be described in a series of defined steps, many of which involve processes related to cytoskeletal dynamics, [...]

How does nucleation of actin initiate lamellipodia formation? In the first phase of lamellipodia formation, actin filament polymerization produces a protrusive force on the cell membrane that promotes the spreading out and enlargement of the lamellipodia. In polarized, migrating cells this is known as [...]

What mechanisms drive extension, pause and stasis of the lamellipodia? Extension of the newly formed actin filament branches occurs at the interface between the leading edge and the existing actin filament network [1] and is maintained by mechanisms such as actin treadmilling. As reviewed [...]

How do focal adhesions act as molecular clutches in lamellipodia? Once formed, focal adhesions essentially act as “molecular clutches”, promoting protrusion at the leading edge whilst suppressing membrane contraction (reviewed in [1] [2][3]). Adhesions aid forward movement by regulating the forces produced by actin [...]

How does force generation within lamellipodia facilitate cell translocation? Interactions between actin filament networks and the focal adhesions to which they are linked results in the generation of forces. These forces may be exerted internally through actin bundle tension and filament network dynamics or [...]

What mechanisms drive retraction of the trailing edge? Protrusion at the front and retraction at the rear are key force-generating processes at the cell periphery that culminate in the translocation of the cell. For forces to be translated into a net forward gain in [...]

What mechanisms drive invadopodia extension? Following initiation by an appropriate signal, the actin cytoskeleton is reorganized to facilitate invadopodia formation. Although several kinases and GTPases are known to influence the transduction of extracellular signaling events leading to F-actin nucleation, there is currently no clear [...]