CAMs and Junctional Complexes Flashcards
How does type IV collagen differ from type I?
Does not form fibrils
Produced by the epithelial tissue, unlike type I which is secreted by fibroblasts
Major component of the basal lamina, three chains (alpha, beta, gamma), has binding sites for (integrins, type IV collagen, entactin, and heparin sulfate-proteogylcans)
LaminIN
Not to be confused with laminA
Fibronectin is made up of what?
Two polypeptide chains cross linked by disulfide bonds
What are the two forms of fibronectin and what can you tell me about them?
Cellular fibronectin- produced by fibroblasts and apart of the extra cellular matrix
Plasma- secreted into the bloodstream and produced by hepatocytes
The four binding sites for fibronectin are?
Fibrin, heparin, collagen, integrin
CAMs can be divided into two groups….
Calcium dependent and calcium INdependent
Calcium dependent CAMs can be further divided into two more groups…
Please welcome the Cadherins and the Selectins!!!
Calcium independent CAMs also have two subgroups
You might have heard of the famous integrins and the immunoglobulin superfamily!!
Cadherins can be even further subdivided into two more categories. Wtf are they?
The very classy and the non classy. For real. Talk about socioeconomic norms
Those classy Cadherins typically form what kind of dimers?
Cis- and trans- homophilic. Ha! Homo. Lol
The classy Cadherins have three distinct types. They are?
E- epithelial (associated with tumor cell metastasis)
N-nervous system
P-placenta
The non classy Cadherins can be found loitering around where and they include these two hooligans…
Found in the desmosomes (macula adheren) and includes the desmocollins and desmogleins
E Cadherin has four extra cellular domains for which ions and they form what kind of dimers?
Calcium ions. Cis- homophilic dimers
The HVA sequences facilitates what kind of E Cadherin dimers?
Trans homophilic
Small proteins that link the cytoplasmic end of Cadherin to cytoplasmic actin
Catenins!
Catenin has three forms. Give them to me now!
Beta and gamma plakoglobin
Alpha catenin
They serve as the major interface between the Cadherins that hold the adjacent cells together and he actin cytoskeleton a of those cells
Catenins
Binds directly to cytoplasmic actin
Alpha catenin
T/F beta catenin serves as a transcription cofactor
True
Selectins bind to what making them apart of the lectins group.
Carbohydrates
This binding site for carbohydrates is located at the extra cellular end of the selectin?
carbohydrate recognition domain (CRD)
What’s required in order for selectin to bind to the CRD?
Calcium
What are the three classes of Selectins
P-platelets
E-activated endothelial cells
L-leukocytes
Integrins bind to two things…
EC matrix and cytoskeleton
The two EC domain molecules that integrin binds to…
Laminin and fibronectin
Integrin binds to this sequence in fibronectin and laminin
RGD (Arginine-Arg, Glycine-Gly, and Aspartic acid-Asp)
What are the three connecting proteins integrin is associated with?
Talin, vinculin, and alpha actinin.
What’s the role of integrin in hemidesmosomes?
To link the basal domain of cells, via intermediate filaments such as keratin, to the EC matrix.
Who are the elite members of the Ig superfamily?
N-cam and I-cam 1 & 2
These are neural adhesion molecules that mediate homo loving and hetero loving interactions.
N-Cam. Probably for the best.
Tell me what the I-CAMs do!
Facilitates the transendothelial migration of leukocytes (our white blood cell friends)
The three wise junctional complexes are?
Adherens (anchoring)
Occludens (tight)
Gap junctions (communicating)
What do adherens do and where can they be found?
They anchor cells together and reinforce the physical integrity of the cell and the tissues they make up. Found on the basolateral surfaces of epithelial cells. (In between the cells)
Establishes an impermeable barrier between adjacent cells that prevents para cellular transport and maintains concentration differences.
Occludens-tight junctions
Gap junctions can be found in where?
Cardiac and neuronal cells
What’s the purpose of a gap junction anyways? Do they need braces?
To rapidly exchange ions and small molecules to coordinate cell activities. And they like their gap
I’m of the Adheren or Occludens variety.
Zonula
Referred to as “belt like” complexes, they are also associated with intracellular actin.
Zonula (Adheren or Occludens)
Maculas are of the adherens variety only but they go by two other names.
Desmosomes and hemidesmosomes
Maculas are very spotty and they like to associate themselves with these “filas”
Intracellular Intermediate filaments (tonofilaments) such as keratin
Pemhigus foliaceus is an autoimmune blistering disease above the stratum spinosum layer in the epidermis. Loss of this Cadherin protein is the cause…
Desmoglein 1
Adherens are anchoring junctions characterized by intracellular spaces filled with what?
Desmoglein and desmocollins
What are the Anchoring junctions that anchor the basal domain of the epithelial cell to the basal lamina
Hemidesmosomes
The hemidesmosome plaque is anchored to the basal lamina on the outer membrane by two things…they are?
Laminin 5 (anchoring filaments) and integrin alpha6beta4
A pair of transmembrane proteins that are responsible for the occlusive properties of the tight junction
Claudins and Occludins
Claudins and Occludins attach intracellularly to which type of zonula Occluden proteins?
ZO-2 & ZO-3
Zonula Occludens have a couple more transmembrane proteins of the fruity kind. What are they and how are they stabilized?
JAMs (junctional adhesion molecules) and Nectin are immunoglobulin loops stabilized by Disulfide bonds
Afadin-Nectin complex is anchored to ZO-1 forming what? The interaction of them forms this.
Cis-homo dimers interact with each other to form trans-homo dimers through the extracellular region.
JAMs are associated intracellularly with?
Afadin and ZO-1
How are focal adhesions different than hemidesmosomes?
The intracellular attachment is NOT to tonofilaments such as keratin but to ACTIN filaments via connecting proteins.
T/F Focal adhesions are integrins.
True
Gap junctions as composed of?…
Connexons
Connexons are made up of?
6 connexins forming a hexagonal structure with a hollow center.
What are Clusters of intracellular channels that allow direct passage of small signaling molecules between adjacent cells to coordinate cell responses.
Gap junctions
Do gap junctions open or close in high concentration of calcium ions?
They Close
This disease Mutation in connexin 32 results in progressive degeneration of peripheral nerves characterized by distal muscle weakness, atrophy, and impairment of deep tendon reflexes.
Charcot Marie tooth demyelination neuropathy
Mutation in connexin 50 is associated with?…
Congenital cataracts, leading to blindness.
Highly expressed in the cochlea, mutations in Cx26 results in?…
Deafness
