Intermediate filaments: from cell architecture to nanomechanics. Type: Article; Author(s): Harald Herrmann, Harald Bär, Laurent Kreplak, Sergei V. Strelkov, Ueli . Intermediate filaments (IFs) constitute a major structural element of animal cells. They build two distinct systems, one in the nucleus and one in the cytoplasm. Herrmann, H. and Baer, H. and Kreplak, L. and Strelkov, S. and Aebi, U.. () Intermediate Filaments: from Cell Architecture to.
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Intermediate filaments: from cell architecture to nanomechanics
Figure 1 Cells from higher metazoan organisms harbor two distinct IF systems. Showing of references.
Figure 4 Schematic representation of the three major phases of cytoplasmic IF assembly. One side of the square is nm long. Taking the comparatively weak interaction between two coil 1A chains as an argument, it was previously suggested that the two-stranded coiled coil of the vimentin dimer may partially open in its coil 1A region to facilitate longitudinal annealing, followed by a lock-in-type reaction, thereby generating stable joints between annealed segments 43 Review Series Free access As a consequence, the skin of people born with defective K14 is highly fragile This effect has been attributed to a failure of mesenchymal contraction at the embryonic wound site Although disease-causing mutations in the coil 1A—consensus motif of keratins do not prevent extended in vitro filament assembly, arguing that they may interfere at the level of the spatial organization of the keratin cytoskeleton, an experimental mutation introduced into this consensus motif of vimentin inhibits in vitro assembly completely 52 — IF proteins are differentially expressed during embryonic development, in parallel to distinct routes of differentiation, indicating that they have distinct tissue-specific functions 67.
Vimentin exhibits a pre-coil domain PCD. Analysis of the effects of the mutation, which led to a deletion of seven amino acids in coil 1B, demonstrated that it compromised desmin IF assembly both in vitro and in transfected cells.
Nonstained, lightly fixed filaments were analyzed by scanning transmission electron microscopy and visualized in a dark field mode first and third panels from the left. Schematic representation of the three major phases of cytoplasmic IF assembly. Conspicuous involvement of desmin tail mutations in diverse cardiac and skeletal myopathies.
Intermediate Filaments: from Cell Architecture to Nanomechanics
Hence, these mutations in K5 and K14 interfere with the proper generation of a functional cytoskeleton and, as a consequence, with the stress-absorbing functions of IFs. In addition, an increasing number of alternative splice forms of individual IF proteins have been discovered recently 5.
The size of the head domain also varies widely and can be as long as amino acids, as in K5 Figure 3 B. In the case of RW, the inter-helical salt bridge formed by the highly conserved aspartate and arginine residues at the end of coil 2B residues andrespectively, in human desmin is destroyed as a consequence of the mutation Figure 6 C.
Intermediate filaments: from cell architecture to nanomechanics.
A quantitative kinetic model for the in vitro assembly of intermediate filaments from tetrameric vimentin. In contrast, the members of the IF protein family, which is encoded by 70 genes, have very different primary amino acid sequences but a common domain organization 4.
From This Paper Figures and tables from this paper. Their interkediate may correlate with the fact that the body plan of plants and fungi depends on mechanical support provided by external cell walls.
The bottom diagram illustrates the force-displacement curve corresponding to the 5 phases shown in the upper panel. This paper has highly influenced 10 other papers. The initial crystallization studies were followed by the determination of the atomic structure of coil 1A and the second half of coil 2, then called coil 2B, for both vimentin and lamin A 43 Comparing the sequences of many different IF proteins, especially over a wide range of species, two amino acid—sequence stretches, the so-called IF-consensus motif s, became evident at either end of the rod Figure 3 A: In the case of the myocyte cytoskeleton, there is further complexity, as it contains IF proteins, such as synemin and syncoilin, that are unable to self-assemble into filaments but need desmin as a scaffold for coassembly, probably by forming heterodimers or higher order complexes with desmin.
In both cases, their major function is assumed to be that of a mechanical stress absorber and an integrating device for the entire cytoskeleton.
Intermediate Filaments: from Cell Architecture to Nanomechanics – edoc
The linker domains between the coils are referred to as L1 which connects coil 1A and coil 1BL12 which connects coil 1B and coil 2Aand L2 which connects coil 2A and coil 2B. The two key questions to be answered if we are to understand the basic principles of IF biology are what is the structure of an IF dimer and, eventually, an entire IF at atomic detail, and how do particular IF proteins assemble into filaments? Herpesviruses and Intermediate Filaments: Adapted with permission from Journal of biological chemistry