Lecture 2 - CAM & Junctional Complexes Flashcards
Describe the major kinds of cell adhesion molecules
(CAMs) and their role in forming cell-to-cell
complexes.
Ca dependant (selectins and cadherins) and independant (Integrins and IG molecules). Also fibronectin and Laminin in the EC matrix. Occludins and adherens(cadherins)
Be able to describe the types of junctional
complexes and relate them to the cohesive nature
of epithelia.
-4 of them HD - intermed - basal, connected to proteins.
MA, - intermed
ZO, ZA - actin
basal lamina is defined as ? and contains what 3 things?
a 50-80 nm thick sheetlike extracellular matrix in direct contact with epithelial cell surfaces. The basal lamina results from the self-assembly of laminin molecules with type IV collagen, entactin, and proteoglycans. STains PAS+
reticular lamina—formed by ?
collagen fibers—supports the basal lamina and is continuous with the connective tissue.
fibronectin has binding sites for ?
integrins, collagen 1-4, heparin sulfate, and fibrin
2 types of fibronectin? which are produced by?
- Plasma fibronectin (produced by hepatocytes) and Cellular fibronectin (by fibroblasts)
Laminin has binding sites for ?
type 4 collagen, entactin, proteoglycans, integrin, dystroglycan
What produces laminin and collagen IV?
Epithelial cells
What produces fibonectin
fibroblasts
Which CAM is associated with zonula occludens and desmosomes?
Cadherins
Which CAM is associated with binding affinities for Sugar?
Selectins
T/F do gap junctions help with Cellular adhesion?
no, they are just assoc. with cellular communication
What are your 2 extracellular proteins that are important for structure? and which collagen fibers do they each interact with? also what type of bond links the polypeptide chains of these 2 proteins?
Fibronectin (1-4) and Laminin(4)
disulfide bonds
Desmocollins and desmogleins belong to which group of CAM’s?
Cadherins
Which CAMs bind to molecules in the extracellular matrix such as fibronectin and laminin?
Integrins
which molecular complexes anchor cells together and reinforce the integrity of tissues?
Zonula Adherens
Mutation in which CAM causes blistering?
Hemidesmosomes.
Do collagen and proteoglycans interact directly or indirectly with the basal domain of epithelial cells?
they interact with the basal membrane, but binding to fibronectin and laminin, so Only Indirect interaction.
Because selectins bind carbohydrates, what group do they belong to?
lectin group
Zonula Occludins are known for and are a type of?
preventing paracellular transport and are a cadherin, like the adherens.
Gap junctions are composed of
6 connexin monomers, in a hexagonal structure with a hollow center that is a hydrophobic intercellular channel
Integrins aka focal adhesions are unique in that they?
- they attached to actin via the EC proteins (fibronectin and laminin) rather than tonofilaments
Gap junctions close when what occurs ?
Ca ion concentrations are high
Integrins are known to be very stable. whats the likelihood that they may turn over and allow the cell to move?
They can do both, depending on the location and the circumstance.
Difference b/w the macula and zonula adherens?
Zonula are belt desmosomes assoc. with actin, and Macula adherencs are spot desmosomes and assoc. with intermediate filaments.
Another name for intracellular intermediate filaments?
tonofilaments -
Tonofilaments are associated with which 2 junctional complexes?
Hemidesmosomes and Macula adherens
How many junctional complexes? name them
4, hemidesmosomes, zonula adherens, zonula occludens, macula adherens
What are the 3 major ways Hemidesmosomes are different from the other junct. complexes?
its the only Non symetrical one and in the basal domain and connects to protein molecules in the EC. (integrins are CAM’s not Junct. Comp’s)
Cadherins structure is known as a ?
cis homophillic dimer
What protein(s) is/are associated with the zonula occludens junctional complex that is/are responsible for the occlusive properties of tight junctions?
Claudins and occludins
how do claudins and occludins attach intracellularly to zonula occludens?
through proteins ZO-2 and ZO-3
2 transmembrane proteins that are members of the immunglobulin superfamily and facilitate cell adhesion
JAMS (junctional adhesion molec)
Nectin
Which intracellular molecule(s) are associated with immunoglobin superfamily proteins JAMS & Nectin?
Afadin - associated with IGS JAMS and Nectin
ZO-1 - assoc. with IGS JAMS
3 classes of Selectins?
LEP- Leukocytes, Endothelial, Platelets
CRD domain is for what? and whats required for activity progression?
Carbohydrate Recognition Domain for Selectins,
Calcium is required, for binding activity
3 locations of cadherins. named for location?
PEN, placenta, epithelial tissues, nerve cells. Our focus on E.
The zona adherens is associated with Actin microfilaments through the interactions between?
The cadherins DESMOCOLLINS & DESMOGLEINS with CATENINS
For cadherin molecules, referring to their structure being Cis or trans means?
Cis is on the same cell and trans is on 2 different cells.
what are catenins?
These are small proteins that link the cytoplasmic end of a cadherin with cytoplasmic actin.
How many catenin forms are there?
Three,
Beta, gamma - attaches to cytoplasmic end of cadherin
and alpha. (binds directly to actin.)
