Extracellular Structures and Junctions - Bringing it All Together

group of protein filaments that are the most stable components of the cytoskeleton of eukaryotic cells; exhibits a diameter of 8–12 nm, which is intermediate between the diameters of actin microfilaments and microtubules

Because tumor cells retain the IF proteins characteristic of the tissue of origin, regardless of where the tumor occurs in the body

Dimer subunits, each w/homologous central rodlike domain of 4 alpha-helices interspersed with 3 short linker segments; 2 dimers form a tetramer, which overlap to form protofilament Central domain flanked by N and C terminal domains (differ in size, sequence, and function) Fibrous Not polarized

The nuclear lamina, composed of 3 IF proteins, become phosphorylated and disassemble as part of the nuclear envelope breakdown at the beginning of mitosis. After mitosis, lamin phosphatases remove the phosphate groups, allowing the nuclear envelope to form again.

Microtubules resist bending; microfilaments are contractile elements that generate tension. Intermediate filaments are elastic and can withstand tensile forces.

They are linker proteins that integrate intermediate filaments, microtubules, and microfilaments, creating a cytoskeletal network.

cell-cell junctions that create an impermeable seal between two cells, preventing fluids, molecules, and ions from crossing a cell layer via the intracellular space

cell-cell junctions that provide adhesive attachments between cells, connecting to F-actin

cell-cell junctions that provide direct chemical and electrical communication between cells via passage of small molecules and ions from one cell to another

cell-cell junctions that provide spot welds between cells, connected to intermediate filaments

cell-ECM junctions that attach the basal surfaces of epithelial cells to the basal lamina; they are anchored to intermediate filaments

homophilic - cells interact with identical molecules on the surface of the cell they adhere to heterophilic - cells interact with different molecules on the surface of the cell they adhere to

in multicellular eukaryotes

determines physical properties of a tissue regulates cel behavior provides positional information lattice upon which cells move reservoir of signaling molecules

found at sites of cell-cell adhesion, cadherins have structurally similar domains in their extracellular, transmembrane domain and widely varying cytosolic ends extracellular domains allow them to zip together in a homophilic fashion, interlocking 2 cells after calcium binds to and stabilizes the extracellular region of cadherins Associate with cytoskeleton at their cytosolic ends

Often, they stop expressing them on their surfaces. This causes them to undergo an epithelial-mesenchymal transition that healthy cells would not. Those cells are spread to other parts of the body via metastasis.