Lecture 3: Cell adhesion Flashcards
What do polarized cells do
- Define inside vs outside
- Have different functions at different cell regions
What does the extracellular matrix do
Directly bears mechanical stresses of tension and compression
How are mechanical STRESSES TRANSMITTED FORM CELL TO CELL
by cytoskeletal filaments anchored to cel-matrix and cell-cell adhesion sites
Connective or epithelial tissue
epithelial cells are cells directly connected to each other with minimal extracellular matrix
connective tissue are cess through the extracellular matrix
What do epithelial cells do
line surfaces, cavities, and organs
Mature polarized epithelial cells are….and what do they do
They are polarized
they define inside vs outside
What does epithelial structure and function require ?
junctional complexes
What are some types of junctional complexes ?
tight junctions
* tight junctions
cell -cell anchoring junctions
* adherents junction
* desmosome
channel forming junction
* gap junction
cell -matrix anchoring junction
* actin-linked cell-matrix junction
* hemidesmosome
What are tight junctions
- they seal the gap between epithelial cells
- prevents things from going between cells
- form sealing strands all along the region between the two cells
What are adherens junctions
connects actin filament bundle in one cell with that in the next cell
* actin does not go through to the other side
What are desmosomes
- connects intermediate filaments in one cell to those in the next cell
- they don’t go through , they just anchor at specific spots
What are gap junction
allows the passage of small water- soluble molecules from cell-cell
What are hemidesmosomes
anchors intermediate filaments in the cell to extracellular matrix
What are Actin- linked cell- matrix junction
anchors actin filaments in cell to extracellular matrix
what are cell-cell junctions mediated by
what are cell- extracellular matrix junctions mediated by
*cadherins
*integrins
cytoskeleton may be …
actin/ intermediated filament
What are cadherins
- transmembrane proteins expressed by both cells
*in a perpendicular arrangement - mediate cell-cell connections at adherens junction
How do extracellular domains directly interact with each other ?
- Cadherins interact homophilic interactions of their extracellular domains
- Interactions require Ca2+
- only one type of cadherin only interacts with other cadherins of the same type
How do cells sort into groups based on homophobic cadherin interactions
- Homophilic interactions from between cells expressing E-cadherins
- Homophilic interactions from between cells expressing N-cadherins
- No heterophilic interactions occur between E-cadherins & N-cadherins
- Result: cells expressing different cadherins sort into two separate groups that do not interact
How do Cadherin intracellular domains indirectly interact with actin
- Cadherins form homophilic interactions with their extracellular domains to directly link adjacent cells
- Cadherins indirectly interact with actin filaments
- These interactions indirectly link the actin cytoskeleton between adjacent cells in epithelial tissues
Which of the following most closely resembles adherens junctions mutations in the outer epithelium of Drosophila embryos?
a) Hemidesmosome mutation in the outer epithelium.
b) Calcium removal at the outer epithelium.
c) Intermediate filament depolymerization in the outer epithelium.
d) Occludin mutation in the outer epithelium.
b
How do adhesion belts & sorting mediate morphogenesis ?
- Adhesion belt contraction pulls cells to form a tube
- Cells express different cadherins to establish new interactions and ensure neural tube closure
What do adhesion belts mediate ?
- morphogenesis
- embryo development
How do tight junctions define domains of the cell
- Apical domain faces the surface, cavity, or organ
- Basal domain
faces the inside of the body - Basal & lateral domains often grouped into the basolateral domain
- Domains are defined and maintained by tight junctions
