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Related Concept Videos

Disassembly of Intermediate Filaments01:35

Disassembly of Intermediate Filaments

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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...
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Types of Intermediate Filaments01:31

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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...
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Formation of Intermediate Filaments00:57

Formation of Intermediate Filaments

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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...
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The Structure of Intermediate Filaments01:19

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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.
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The Evidence for Evolution02:55

The Evidence for Evolution

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Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of novel varieties and entire new species. These changes are responsible for the diverse forms of life inhabiting the planet. The evidence for evolution suggests that all living organisms descended from common ancestors.
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Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure leads to the rise of similar but unrelated adaptations in organisms with no recent common ancestors, a process known as convergent evolution.
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Updated: Feb 12, 2026

Isolation of Intermediate Filament Proteins from Multiple Mouse Tissues to Study Aging-associated Post-translational Modifications
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Isolation of Intermediate Filament Proteins from Multiple Mouse Tissues to Study Aging-associated Post-translational Modifications

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Intermediate filament protein evolution and protists.

Harald Preisner1, Jörn Habicht1, Sriram G Garg1

  • 1Institute for Molecular Evolution, Heinrich-Heine-University, Düsseldorf, Germany.

Cytoskeleton (Hoboken, N.J.)
|March 25, 2018
PubMed
Summary
This summary is machine-generated.

Intermediate filaments (IFs) are not exclusive to animals; they originated in protists. Their evolution showcases convergent development, leading to diverse forms in eukaryotes.

Keywords:
cytoskeletoneukaryote evolutionintermediate filamentslaminsmulticellularity

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Area of Science:

  • Evolutionary biology
  • Cell biology
  • Biochemistry

Background:

  • Eukaryotic cytoskeleton relies on actin and tubulin, with intermediate filaments (IFs) traditionally considered metazoan-specific.
  • IF proteins like lamin, vimentin, and keratin are difficult to identify phylogenetically in non-metazoans.
  • Numerous protist cytoskeletal proteins share structural/functional traits with metazoan IFs.

Purpose of the Study:

  • To re-evaluate the evolutionary origins and definition of intermediate filament proteins.
  • To integrate protist filament-forming proteins into the broader understanding of IF evolution.
  • To explore the diversification mechanisms of IF proteins across eukaryotes.

Main Methods:

  • Review of existing literature on IF protein discovery in metazoans and protists.
  • Phylogenetic analysis and comparison of cytoskeletal protein structures and functions.
  • Integration of recent findings on lamins across eukaryotic supergroups.

Main Results:

  • IF proteins likely evolved in protists, not metazoans.
  • Convergent evolution and rapid protein evolution contributed to IF diversity.
  • Cytosolic IF proteins, originating from nuclear lamins, uniquely emerged with animal multicellularity.

Conclusions:

  • The definition of intermediate filaments should encompass protist proteins.
  • IF evolution is a prime example of convergent evolution within eukaryotes.
  • The unique emergence of cytosolic IFs in animals is linked to multicellularity.