cell junctions and cytoskeleton

The cytoskeleton: a complex and dynamic network of interconnected protein filaments, exists in the cytoplasm of all cells, spanning from bacteria and archaea to eukaryotes. It stretches from the cell nucleus to the cell membrane and is comprised of similar proteins across different organisms. This structural framework consists of three key components: microfilaments, intermediate filaments, and microtubules, all of which exhibit the ability to rapidly grow or disassemble, adapting to the specific needs of the cell.

Microtubule dynamics: are further modified in the cell by interaction with cellular factors that stabilize or destabilize microtubules, which operate in both spatially and temporally specific ways to generate different microtubule assemblies during the cell cycle. There are a α- and β-tubulin monomers.

Intermediate filaments (IFs): are a diverse, integral, and ubiquitous component of the nuclear and cytoplasmic cytoskeleton in metazoans. More than 70 genes, partitioned in six major classes, encode IF-forming proteins and are regulated in a tissue-specific and differentiation-dependent fashion.

The role of microfilaments in generating cell locomotion has been investigated in glial cells migrating in vitro. Such cells are found to contain two types of microfilament systems: First, sheath is present in the cytoplasm at the base of the cells, just inside the plasma membrane, and in cell processes. Second, a network is found just beneath the plasma membrane at the leading edge (undulating membrane locomotory organelle) and along the sides of the cell.

Gap junctions: involve pairs of identical membrane proteins linked together in dyads, forming bridges across the extracellular space between two adjacent cell membranes.