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16: Cell Junctons and the Cytoskeleton

Terms in this set (31)

Name 5 types of cell junctions.
1) Tight junctions
2) Zona Adherens (belt desmosomes)
3) Macula Adherens (spot desmosomes)
4) Hemidesmosomes
5) Gap Junctions
Which junction is not associated with the cytoskeleton?
Gap junctions
What is the function of tight junctions?
Link adjacent epithelial cells at the apical domain. They regulate the passage of water and the flux of ions between adjacent cells (paracellular).
What are the proteins that make up the tight junction?
1) Afadin-nectin
2) Junctional adhesion molecules (JAMs)
3) Occludin and claudins
What cytoskeletal protein do tight junctions interact with?
F-actin
What is the function of Zonula occludins in the tight junction?
Zonula occludins facilitate the interaction of F-actin with occludins, claudins, and JAMs.
What is the function of the zonula adherens?
Maintain the sheet-like organization of epithelial cells via the actin cytoskeleton.
What is another name for zonula adherens?
Belt Desmosomes
What are the proteins associated with the zonula adherens?
1) afadin-nectin
2) cadherins
3) plaque
4) catenin
5) actin
Which part of the zonula adherens interacts with the actin cytoskeleton?
Plaque and catenin complex
What is another name for macula adherens?
spot desmosomes
What proteins make up the macula adherens?
1) Plaques
2) Cadherins
3) Keratin intermediate filaments
What is Naxos disease caused by and what are the physiologic consequences?
Defect in plakoglobin (plaque) resulting in the loss of normal demosomal structure affecting the heart and hair. The animal will have cardiomyopathy and wooly hair coat syndrome.
What is pemphigus foliaceus?
An autoantibody-mediated blistering disease in which antibodies against desmoglein 1 (a plaque) cause a loss of adhesion of keratinocytes in the superficial layers of the epidermis. Forms bullae (blister) either within or below the epidermis.
What is the function of hemidesmosomes?
They are the mechanism by which integrins and lamina 5 interact with the keratin (intermediate filament) cytoskeleton and the basal lamina to facilitate adhesion at the basal aspect of the epithelia.
What are three key features of integrins?
1) They have two subunits
2) They have a dual function: they bind to the extracellular matrix (fibronectin) and the internal cytoskeleton (actin)
3) Require divalent cations to be active.
What is a gap junction?
The intercellular channel that allows the direct passage of small signaling molecules between adjacent cells to coordinate cell responses.
How are gap junctions formed (physiologic structure)?
Six connexin monomers assemble to form a hexameric connexon, a cylinder with a central open channel.
Will null connexin mice (-/-) survive?
No this mutation is embryonically leathal.
What are the two major classes of adherins junctions?
1) Calcium dependent (cadherins and selectins)
2) Calcium independent (immunoglobulin super family and integrins)
What are the major roles of cadherin?
cell adhesion, morphogenesis, and they play a major role in metastasis.
What are the major roles of selectin?
Bind carbohydrates, diapedesis (movement of WBC to tissue), blood cell and blood vessel interactions, and homing
What are the major roles of the IgG superfamily?
Cell adhesion molecules, inflammation, and morphogenesis.
What adhesion protein holds epithelial cells together in a sheet arrangement?
Cadherins
That is the physiologic structure of the cadherin?
Four domains in the extracellular portion of the cadherin bind calcium (calcium dependent). Three catenin proteins facilitate interaction with actin filaments on the cytosolic side.
What happens to cadherins when calcium is removed?
Loose function of cadherins and disrupt tissue cohesiveness.
Name 3 cytoskeleton families.
1) Actin
2) Microtubules
3) Intermediate filaments
Name some functions of the cytoskeleton.
1) 3D network throughout cell
2) essential for cell locomotion
3) required for the maintenance as well as changes in cell shape
4) specialized apical features of the epithelium
5) cytokinesis
6) phagocytosis
7) cellular support and strength
8) cytoplasmic components of cell-cell and cell-ECM adhesion
What is the function of microtubules?
to transport cellular cargo via kinesin or dyneins.
What is the function of intermediate filaments?
They give mechanical strength to cells and carry mechanical stresses in a tissue layer by spanning the cytoplasm from one cell-cell junction to another.
What is a brush border?
Formed by a closely packed layer of microvilli at the apical domain of the interstitial columnar epithelial cells or in cuboidal epithelial cells of the proximal convoluted tubule.
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