Many cellular processes are powered by cytoskeletal assemblies. contraction can be due to the minus ends from the microtubules clustering collectively because of the activities of the motor protein known as dynein. To check this fundamental idea, Foster et al. created a numerical model predicated on an ‘energetic liquid’ theory. This model makes predictions that consent very well using the experimental data. The next phase in this function is to learn if this style of microtubule contraction pertains to various other systems of microtubules. DOI: http://dx.doi.org/10.7554/eLife.10837.002 Launch The mechanics, movements, and internal organization of eukaryotic cells are dependant on the cytoskeleton largely. The cytoskeleton consists of filaments, such as actin and microtubules, and molecular motors, which consume chemical energy to exert forces on and arrange the filaments into large-scale networks. Motor proteins, including dynein and roughly 14 different families of kinesin (Wordeman, 2010), organize microtubules to form the spindle, which segregates chromosomes during cell division. The motor protein myosin organizes actin filaments into networks which drive cell motility, polarity, cytokinesis, Istradefylline cell signaling and left-right symmetry breakage (Mitchinson and Cramer, 1996; Mayer et al., 2010; Naganathan et al., 2014). The non-equilibrium nature of motor activity is essential for the organization of the cytoskeleton into these diverse sub-cellular structures, but it remains unclear how the interactions between filaments, different motor proteins, and other biomolecules influence the behaviors of the networks they form. In particular, it is difficult to extrapolate from the biochemical properties of motors characterized in reconstituted systems to the biological function of those motors extracts, which recapitulate the biochemical complexity of the system. The self-organization of cytoskeletal filaments has been extensively studied in cell extracts and in reconstituted systems of purified components. Actin can form macroscopic networks that exhibit a myosin-dependent bulk contraction (Murrell and Gardel, 2012; Bendix et al., 2008; K?hler and Bausch, 2012; Alvarado et al., 2013; Szent-Gy?rgyi, 1943). Microtubule networks purified from neuronal extracts have also been observed to undergo bulk contraction (Weisenberg and Cianci, 1984), while microtubules in mitotic and meiotic extracts are found to assemble into asters (Gaglio Istradefylline cell signaling et al., 1995; Mountain et al., 1999; Verde et al., 1991). Aster formation in meiotic egg extracts is usually dynein-dependent, and has been proposed to be driven by the clustering of Rabbit polyclonal to Complement C3 beta chain microtubule minus ends by dynein (Verde et al., 1991). It has also been suggested that dynein binds to the minus Istradefylline cell signaling ends of microtubules Istradefylline cell signaling in spindles and clusters the minus ends of microtubules to form spindle poles (Heald et al., 1996; Burbank et al., 2007; Khodjakov et al., 2003; Goshima et al., 2005; Elting et al., 2014) and dynein has been shown to accumulate on microtubule minus ends in a purified system (McKenney et al., 2014). Purified solutions of microtubules and kinesin can also form asters (Ndlec et al., 1997; Hentrich and Surrey, 2010; Urrutia et al., 1991), or under other conditions, dynamic liquid crystalline networks (Sanchez et al., 2012). Hydrodynamic theories have been proposed to describe the behaviors of cytoskeletal networks on length scales that are much greater than the size of individual filaments and motor proteins (Prost et al., 2015, Marchetti et al., 2013). These phenomenological theories are based on symmetries and general principles of non-equilibrium physics, with the details of the microscopic process captured by a small number of effective parameters. As hydrodynamic theories are formulated at the continuum level, they cannot be used to derive the values of their associated parameters, which must be obtained from more microscopic theories (Prost et al., 2015, Marchetti et al., 2013) or by comparison to experiments (Mayer et al., 2010; Brugus and Needleman, 2014). A key feature of networks of cytoskeletal filaments and motor proteins that enters hydrodynamic theories, and differentiates these non-equilibrium systems from passive polymer networks, is the presence of additional, active stresses (Prost et al., 2015, Marchetti et al., 2013). These active stresses can be contractile or extensile, with profound implications Istradefylline cell signaling for the large-scale behavior of cytoskeletal networks. Contractile stresses can result from a favored association of motors.