How is microtubule assembly/disassembly regulated? GTP hydrolysis has been shown to be a key regulator of microtubule polymerization dynamics. Although the exact mechanisms are poorly understood, two opposing models have been proposed to describe how GTP could alter the conformation of α-tubulin/β-tubulin from the [...]

What is microtubule dynamic instability? In most cell types, thirteen protofilaments associate laterally to form a microtubule. In a few cases microtubules contain more or fewer protofilaments [1]. Numerous interactions between the subunits give microtubules their stiffness and resistance to bending forces. The lateral [...]

What is the role of microtubules in mechanotransduction? Microtubules exist in all cells, however their influence in the mechanotransduction of mechanical stimuli has been described at length in cardiac striated muscle [1]. Mechanical stimuli also affect microtubule formation and proliferation. This has been observed [...]

What are Contractile Fibers? Certain myosin isoforms (i.e. myosin II) form bipolar assemblies via the extended coiled-coil domains in the heavy chains (see also “thick filaments”). Actin “thin filaments” with opposite polarity associate with thick filaments to create contractile bundles that can be found [...]

What is Actomyosin? Actomyosin refers to the actin-myosin complex that forms within the cytoskeleton. Actomyosin is inherently contractile, with the myosin motor protein able to pull on actin filaments. This property gives rise to contractile fibers that form the basis of skeletal muscle, and [...]

How does the contractome protein network regulate actomyosin contractility? Non-muscle myosin II isoforms have a similar structure and function to their muscle equivalents. However, their interaction with actin serves to generate cellular forces rather than muscular contraction. During non-muscle actomyosin contractility, non-muscle myosin II [...]

How do blebs expand? Expansion lasts between 5 to 30 seconds, following bleb initiation and preceding reformation of the cortical actomyosin cytoskeleton just beneath the membrane [1]. During this time, the bleb proceeds to grow as a result of actomyosin driven pressure, resulting in [...]

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 [...]

How do filopodia attach to the surrounding substrate? A diverse array of cellular responses can result when a filopodium makes contact with a ligand or substrate. These responses are dependent on the coupling of membrane-bound proteins to the backward (retrograde) flow of actin that [...]

How do filopodia pull on a substrate? Although a reterograde motion of actin filaments is intrinsic in the formation of filopodia, the forces generated by actin treadmilling are too weak to facilitate the “pulling” mechanism required for rigidity sensing and other mechanosensing processes. This [...]