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Softness, strength and self-repair in intermediate filament networks
Oliver I Wagner1, Sebastian Rammensee, Neha Korde
1Department of Physiology, Institute for Medicine and Engineering, University of Pennsylvania, 1010 Vagelos Laboratories, 3340 Smith Walk, Philadelphia, PA 19104, USA.
Experimental Cell Research
|May 26, 2007
Summary
Intermediate filaments (IFs) provide cellular mechanical resilience, offering compliance to minor stress and strength against major forces. Their unique elasticity and rapid recovery after damage highlight their critical role in cell mechanics.
Area of Science:
- Cellular mechanics and biophysics
- Cytoskeletal dynamics and polymer physics
Background:
- Intermediate filaments (IFs) are crucial cytoskeletal components involved in cellular mechanical functions.
- Understanding how IFs provide both compliance and strength is key to cell biology.
Purpose of the Study:
- To elucidate the mechanical properties of intermediate filaments (IFs) at the single polymer and network levels.
- To investigate the unique resilience and recovery mechanisms of IF networks compared to other cytoskeletal elements.
Main Methods:
- Analysis of elastic properties of single IF protein polymers.
- Viscoelastic characterization of IF networks.
- Mechanical disruption and recovery assays of IF gels.
Main Results:
- Single IFs exhibit significant extensibility, stretching over 3 times their initial length.
- IF networks withstand large strains (>100%) without permanent damage.
- Disrupted IF gels demonstrate rapid elastic modulus recovery, unlike actin filament gels.
Conclusions:
- Intermediate filaments possess unique mechanical properties enabling cellular resilience.
- Their ability to withstand and recover from large deformations is a key characteristic.
- Further research is needed to identify in vivo mechanisms of IF network formation and crossbridging.
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01:35Disassembly of Intermediate Filaments
Intermediate filaments (IFs) do not undergo spontaneous disassembly. Enzymes, kinases, and phosphatases add and remove phosphates from specific sites to regulate their disassembly. The IF concentration in the cytoplasm also regulates the disassembly. If the concentration crosses a threshold, it activates the protein kinases in the vicinity, allowing the phosphorylation of IFs.
Keratin proteins, found at the cell periphery near cell junctions, undergo a cycle of assembly and disassembly. In Type...
Keratin proteins, found at the cell periphery near cell junctions, undergo a cycle of assembly and disassembly. In Type...
00:57Formation of Intermediate Filaments
Intermediate filaments are cytoskeletal proteins with higher tensile strength and flexibility than microfilaments and microtubules. Unlike the other two cytoskeletal proteins, intermediate filament formation lacks the enzymatic activity to hydrolyze nucleotides like ATP and GTP to generate energy for polymerization. Therefore, the formation of intermediate filaments is multistep self-assembly. The involvement of any accessory proteins in intermediate filament formation has not yet been reported.
01:19The Structure of Intermediate Filaments
The intermediate filaments are one of three widely studied cytoskeletal filaments. They are so named as their diameter (10 nm) is in between that of microfilaments (7 nm) and the microtubules (25 nm). These filaments are highly stable and can remain intact when exposed to high salt concentrations and detergents. These filaments are responsible for providing stability and mechanical support to the cells. They also help in cell adhesion and maintaining tissue integrity.
Intermediate filaments...
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01:31Types of Intermediate Filaments
The intermediate filaments are an essential component of the cytoskeleton. Presently six types of intermediate filament have been identified. Type I and II are acidic and basic keratin proteins. Type III is of mesodermal origin and comprises four proteins: vimentin, desmin, glial fibrillary acidic protein (GFAP), and peripherin. Vimentin is commonly found in mesenchymal cells, desmin in muscle cells, GFAP in astrocytes, while peripherin is found in peripheral nervous system neurons (PNS). Type...
01:18Assembly of Cytoskeletal Filaments
Cytoskeletal filaments are polymeric forms of smaller protein subunits. However, individual cytoskeletal filaments may easily disassemble or associate with other similar filaments to form rigid structures. Microfilaments, made of actin monomers, rely on actin-binding proteins to form bundles and create networks of individual actin filaments. Microtubules rely on microtubule-associated proteins (MAPs) to form sturdy cylindrical structures. However, the proteins involved in forming complex...
01:12Adaptability of Cytoskeletal Filaments
The cytoskeleton is a complex dynamic structure performing varied functions based on cellular requirements. The adaptability of the individual filaments in the cytoskeleton determines their ability to perform various functions within the cell. It can undergo rapid reorganization during processes like cell division or remain stable for several hours as in the interphase. The adaptability of these filaments depends on stringent regulatory mechanisms. The microfilament and microtubules of the...