Extracellular Structures and Junctions - Bringing it All Together Flashcards
Lecture 29
What are intermediate filaments? What are their diameter? In relation to microfilaments and microtubules?
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
Why is intermediate filament typing useful in diagnosing cancer?
Because tumor cells retain the IF proteins characteristic of the tissue of origin, regardless of where the tumor occurs in the body
Describe intermediate filaments.
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
How can intermediate filaments by dynamically remodeled during mitosis?
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.
Compare microfilaments to microtubules during compression.
Microtubules resist bending; microfilaments are contractile elements that generate tension. Intermediate filaments are elastic and can withstand tensile forces.
What are spectraplakins and what do they do?
They are linker proteins that integrate intermediate filaments, microtubules, and microfilaments, creating a cytoskeletal network.
What are tight junctions?
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
What are adherens?
cell-cell junctions that provide adhesive attachments between cells, connecting to F-actin
What are gap junctions?
cell-cell junctions that provide direct chemical and electrical communication between cells via passage of small molecules and ions from one cell to another
What are desmosomes?
cell-cell junctions that provide spot welds between cells, connected to intermediate filaments
What are hemidesmosomes?
cell-ECM junctions that attach the basal surfaces of epithelial cells to the basal lamina; they are anchored to intermediate filaments
What are homophilic and heterophilic interactions?
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
Where are intermediate filaments found?
in multicellular eukaryotes
What does the extracellular matrix of animal cells do?
determines physical properties of a tissue
regulates cel behavior
provides positional information
lattice upon which cells move
reservoir of signaling molecules
What are cadherins? Where are they found?They
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
