Cell Adhesion Flashcards
How are mechanical stresses transmitted from cell to cell?
By cytoskeletal filaments anchored to cell-matrix and cell-cell adhesion sites.
What does the extracellular matrix bear?
Mechanical stresses of tension and compression
Epithelial tissues
Cells are directly connected with a minimal extracellular matrix
Epithelial tissue can include basal lamina
Connective tissues
Cells dispersed through extracellular matrix
The function of epithelial cells
Lines surfaces, cavities, and organs
eg. skin, digestive tract
Are epithelial cells polarized
yes
order of junctional complexes in epithelial cells (mature)
tight junctions, adherens junctions desmosomes, gap junctions
actin linked and hemidesmosome (in basal region)
tight junctions
seals the gap between epithelial cells
form sealing strands
cell-cell anchoring junctions
adherens junctions and desmosomes
adherens junctions
connects actin filament bundle in one cell with that in the next cell
form adhesion belts. actin filaments don’t go through to other side.
desmosome
connects intermediate filaments in one cell to those in the next cell
channel forming junction
gap junction
gap junction
allows the passage of small water-soluble molecules from cell to cell
cell-matrix anchoring junctions
actin-linked cell-matrix junction and hemidesmosome
actin-linked cell-matrix junction
anchors actin filaments in cell to extracellular matrix
hemidesmosome
anchors intermediate filaments in cells to extracellular matrix
how are cell-cell junctions mediated?
cadherins
how are cell-extracellular matrix junctions mediated?
integrins
What can the cytoskeleton be
actin or intermediate filaments
cadherins
adherens junctions
they are transmembrane proteins expressed by both cells
Cadherin interactions
Cadherins interact homophilic interactions of their extracellular domains
These interactions require Ca2+
How do cells sort into groups based on homophilic 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
What do cadherins indirectly interact with?
actin
These interactions indirectly link the
actin cytoskeleton between adjacent
cells in epithelial tissues
what can adhesion belts mediate
morphogenesis
Neural tube closure
Adhesion belt contraction pulls cells to form a tube
Cells express different cadherins to establish new interactions and ensure neural tube closure
How do tight junctions define domains of the cell?
Apical domain faces the surface, cavity, or organ
* Domains are defined and maintained by tight junctions
* Basal domain faces the inside of the body
* Basal & lateral domains often grouped into the basolateral domain
What forms tight junctions
claudins and occludins
what type of interactions do claudins and occludins have
homophilic interactions with their
extracellular domains to directly link
adjacent cells
* Many rows of these proteins form a
functional tight junction
Why do tight junctions help
they limit diffusion in the extracellular space
prevent membrane proteins from
moving between the apical and
basolateral domains
Tight junctions regulate what enters and organism
Tight junctions stop anything from directly diffusing from the gut lumen into connective tissue & blood
Active transporters must move
glucose into the epithelial cell on the
apical domain
Passive carriers in the basolateral domain allow glucose to diffuse out of the epithelial cell into the connective tissue/blood
Tight junctions keep the correct transporters in their correct domains of the cell
what mediates cell to cell matrix junctions
integrin heterodimers
how do Integrins anchor actin filaments to the extracellular matrix
Integrin heterodimers directly bind extracellular matrix proteins
Integrins have a transmembrane domain
Integrins indirectly interact with actin filaments
Actin-integrin-extracellular matrix interactions can provide the adhesion necessary for cell migration
how do polarity cues establish cell cohesion
Adherens junctions form first
* Adherens junctions provide polarity
cues to define apical from
basolateral domains
* Tight junctions form apical to the
adherens junctions
