@article{HuberSchnaussRoenickeetal.2013, author = {Huber, Florian and Schnauß, J{\"o}rg and R{\"o}nicke, S. and Rauch, P. and M{\"u}ller, K. and F{\"u}tterer, C. and K{\"a}s, Josef}, title = {Emergent complexity of the cytoskeleton: from single filaments to tissue}, series = {Advances in Physics}, volume = {62}, journal = {Advances in Physics}, number = {1}, publisher = {Taylor \& Francis}, issn = {1460-6976}, doi = {10.1080/00018732.2013.771509}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-34812}, pages = {1 -- 112}, year = {2013}, abstract = {Despite their overwhelming complexity, living cells display a high degree of internal mechanical and functional organization which can largely be attributed to the intracellular biopolymer scaffold, the cytoskeleton. Being a very complex system far from thermodynamic equilibrium, the cytoskeleton's ability to organize is at the same time challenging and fascinating. The extensive amounts of frequently interacting cellular building blocks and their inherent multifunctionality permits highly adaptive behavior and obstructs a purely reductionist approach. Nevertheless (and despite the field's relative novelty), the physics approach has already proved to be extremely successful in revealing very fundamental concepts of cytoskeleton organization and behavior. This review aims at introducing the physics of the cytoskeleton ranging from single biopolymer filaments to multicellular organisms. Throughout this wide range of phenomena, the focus is set on the intertwined nature of the different physical scales (levels of complexity) that give rise to numerous emergent properties by means of self-organization or self-assembly.}, language = {en} } @article{HuberStrehleSchnaussetal.2015, author = {Huber, Florian and Strehle, Dan and Schnauß, J{\"o}rg and K{\"a}s, Josef}, title = {Formation of regularly spaced networks as a general feature of actin bundle condensation by entropic forces}, series = {New Journal of Physics}, volume = {17}, journal = {New Journal of Physics}, number = {4}, publisher = {IOP Publishing}, issn = {1367-2630}, doi = {10.1088/1367-2630/17/4/043029}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-34833}, year = {2015}, language = {en} } @article{HuberKaesStuhrmann2008, author = {Huber, Florian and K{\"a}s, Josef and Stuhrmann, Bj{\"o}rn}, title = {Growing actin networks form lamellipodium and lamellum by self-assembly}, series = {Biophysical Journal}, volume = {95}, journal = {Biophysical Journal}, number = {12}, publisher = {Biophysical Society}, issn = {1542-0086}, doi = {10.1529/biophysj.108.134817}, pages = {5508 -- 5523}, year = {2008}, abstract = {Many different cell types are able to migrate by formation of a thin actin-based cytoskeletal extension. Recently, it became evident that this extension consists of two distinct substructures, designated lamellipodium and lamellum, which differ significantly in their kinetic and kinematic properties as well as their biochemical composition. We developed a stochastic two-dimensional computer simulation that includes chemical reaction kinetics, G-actin diffusion, and filament transport to investigate the formation of growing actin networks in migrating cells. Model parameters were chosen based on experimental data or theoretical considerations. In this work, we demonstrate the system's ability to form two distinct networks by self-organization. We found a characteristic transition in mean filament length as well as a distinct maximum in depolymerization flux, both within the first 1-2 microm. The separation into two distinct substructures was found to be extremely robust with respect to initial conditions and variation of model parameters. We quantitatively investigated the complex interplay between ADF/cofilin and tropomyosin and propose a plausible mechanism that leads to spatial separation of, respectively, ADF/cofilin- or tropomyosin-dominated compartments. Tropomyosin was found to play an important role in stabilizing the lamellar actin network. Furthermore, the influence of filament severing and annealing on the network properties is explored, and simulation data are compared to existing experimental data.}, language = {en} } @article{HuberKaes2011, author = {Huber, Florian and K{\"a}s, Josef}, title = {Self-regulative organization of the cytoskeleton}, series = {Cytoskeleton}, volume = {68}, journal = {Cytoskeleton}, number = {5}, publisher = {Wiley}, issn = {1949-3592}, doi = {10.1002/cm.20509}, pages = {259 -- 265}, year = {2011}, abstract = {Despite its impressive complexity the cytoskeleton succeeds to persistently organize itself and thus the cells' interior. In contrast to classical man-made machines, much of the cellular organization originates from inherent self-assembly and self-organization allowing a high degree of autonomy for various functional units. Recent experimental and theoretical studies revealed numerous examples of cytoskeleton components that arrange and organize in a self-regulative way. In the present review we want to shortly summarize some of the principle mechanisms that are able to inherently trigger and regulate the cytoskeleton organization. Although taken individually most of these regulative principles are rather simple with intuitively predictable consequences, combinations of two or more of these mechanisms can quickly give rise to very complex, unexpected behavior and might even be able to explain the formation of different functional units out of a common pool of available building blocks.}, language = {en} } @article{StuhrmannHuberKaes2011, author = {Stuhrmann, Bj{\"o}rn and Huber, Florian and K{\"a}s, Josef}, title = {Robust organizational principles of protrusive biopolymer networks in migrating living cells}, series = {Plos One}, volume = {6}, journal = {Plos One}, number = {1}, publisher = {Public Library of Science (PLoS)}, issn = {1932-6203}, doi = {10.1371/journal.pone.0014471}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-34901}, year = {2011}, abstract = {Cell migration is associated with the dynamic protrusion of a thin actin-based cytoskeletal extension at the cell front, which has been shown to consist of two different substructures, the leading lamellipodium and the subsequent lamellum. While the formation of the lamellipodium is increasingly well understood, organizational principles underlying the emergence of the lamellum are just beginning to be unraveled. We report here on a 1D mathematical model which describes the reaction-diffusion processes of a polarized actin network in steady state, and reproduces essential characteristics of the lamellipodium-lamellum system. We observe a steep gradient in filament lengths at the protruding edge, a local depolymerization maximum a few microns behind the edge, as well as a differential dominance of the network destabilizer ADF/cofilin and the stabilizer tropomyosin. We identify simple and robust organizational principles giving rise to the derived network characteristics, uncoupled from the specifics of any molecular implementation, and thus plausibly valid across cell types. An analysis of network length dependence on physico-chemical system parameters implies that to limit array treadmilling to cellular dimensions, network growth has to be truncated by mechanisms other than aging-induced depolymerization, e.g., by myosin-associated network dissociation at the transition to the cell body. Our work contributes to the analytical understanding of the cytoskeletal extension's bisection into lamellipodium and lamellum and sheds light on how cells organize their molecular machinery to achieve motility.}, language = {en} } @article{SmithGentryStuhrmannetal.2009, author = {Smith, David and Gentry, Brian and Stuhrmann, Bj{\"o}rn and Huber, Florian and Strehle, D. A.N. and Brunner, Claudia and Koch, Daniel and Steinbeck, Matthias and Betz, Timo and K{\"a}s, Josef A.}, title = {The cytoskeleton: An active polymer-based scaffold}, series = {Biophysical Reviews and Letters}, volume = {04}, journal = {Biophysical Reviews and Letters}, issn = {1793-7035}, doi = {10.1142/S1793048009000983}, pages = {179 -- 208}, year = {2009}, language = {en} }