Cell Junctions and Adhesion Flashcards
Cell junctions are best observed in
Epithelial cells
What are the types of cell junctions?
- ) Tight junctions
- ) Zonula adherens (belt desmosomes)
- ) Macular adherens (spot desmosomes)
- ) Hemidesmosome
- ) Gap (communicating) junctions
Define cell polarityand control the passage of substances between adjacent cells
Tight junctions
Have a distribution like a ribbon internally bracing the cells and are associated with actin filaments
Tight junctions
An anchorage junction that has a beltlike distribution and is associated with actin filaments
Zonula adherens (belt desmosome)
An anchorage junction with a spotlike distribution and is associated with intermediate filaments
Macula Adherens (spot desmosomes)
Link the basal domain of an epithelial cell to the basal lamina. Intermediate filaments are associated with a plaque
Hemidesmosome
Connect functionally two adjacent cells.
-Formed by connexons
Gap junction
Channel-like structures that enable the passage of small molecules
Connexons
Gap junctions are not associated with
Cytoskeletal components
What are the two cell-cell anchorage junctions?
Belt desmosomes and spot desmosomes
What are the cell matrix junctions?
Hemidesmosomes and focal adhesions
The transmembrane proteins for the cell-cell anchor junctions (belt and spot desmosomes) are?
Cytoskeletal?
1.) Cadherins
Actin (belt) Intermediate filaments (spot)
Which two proteins make up tight junctions?
Occludins and Claudins
Encircle the entire cell like a belt
Tight junctions
The apical domain of a cell faces the
Lumen
Tight junctions are composed of “sealing strands” where the two membranes are tightly linked together by lines of
Transmembrane proteins
Mediate the adhesion at tight junctions
Occludins and Claudins
Occludins and claudins are linked to the actin cytoskeleton through adaptor proteins like
ZO-1
Also encircle the entire cell an are positioned right underneath the tight junctions
Belt desmosomes
Transmembrane proteins that mediate adhesion at the belt desmosomes
Cadherins
In order to function, cadherins need
Calcium
Cadherins are linked to the actin cytoskeleton by
Catenins
Catenins are made up of
α, β, and ƴ/plakoglobin
Binds to cadherin and ƴ-catenin/plakoglobin
β-catenin
Binds directly to actin
α-catenin
The main proteins holding epithelial cells together in a sheet
Cadherins