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Types of cell junctions
Transcript of Types of cell junctions
Yasmina Ahmed Yomna Adel Outline: Definition.
Functions. Definition: 1. Occluding (tight) junctions
2. Adhesive junctions:
3.Communicating (gap) junctions Types of intercellular junctions: 1. transmembrane adhesive protein.
2. citoplasmic adaptor protein.
3. cytoskeletal filament. Main components: The opposing cell membranes are
held in close contact by the presence of transmembrane adhesive proteins The term zonula describes a
junction that completely encircles the cell Occluding (tight) junctions
(zonula occludens) : Hold cells together
Control the passage of material through the intercellular spaces
The tightness of of the junction to water and ions depends on the number of strands
Regulation of permeability of tight junctions in some tissues Functions: They hold cells together or anchor them to matrix
The intercellular space in cell-cell junctions is maintained at 20 nm Adhesive junctions Adherens junctions (or zonula adherens, intermediate junction, or "belt desmosome") are protein complexes that occur at cell–cell junctions in epithelial tissues, usually more basal than tight junctions. An adherens junction is defined as a cell junction whose cytoplasmic face is linked to the actin cytoskeleton. They can appear as bands encircling the cell (zonula adherens) or as spots of attachment to the extracellular matrix (adhesion plaques). Cell-cell adhesive junctions
1. zonula adherens In the gap between the two cells, there is a protein called E-cadherin
The cadherins from adjacent cells interact to 'zipper' up the two cells together
Inside the cell E-cadherin binds to catenin, which in turn binds to other proteins in a protein complex with actin filaments Desmosomes connect two cells together
structure: thickening of adjacent cell membrane, a pair of attachment plaques, transemembrane protein and tonofilaments.( cadherin)
The intercellular space is very wide 30nm Cell-to-cell junctions
2. Macula adherens (desmosome) Cell-to-matrix junctions
1. Focal adhesions Cell-to-matrix junctions
2. Hemidesmosomes Communicating (gap) junctions THANKS
for your attention :) Prof. Dr. Wael Abu Zaid Prof. Dr. Mohamed Zayed Prof. Dr. Nehad Samir Specialized junctions form when
cells come into contact with one another
and with the extracellular matrix at specific
sites on the contacting cell membranes. The transmembrane protein is integrin
Actin-binding proteins link the integrins to the actin cytoskeleton
Binding of integrin to extra cellular matrix proteins.
Binding of focal adhesion kinase to the cytoskeleton complex Hemidesmosomes are sites of connections at the base of an epithelial cell with the matrix
The hemidesmosomes connect the cell to the basal lamina via keratin intermediate filaments ANY QUESTIONS ? Are cylindrical inter cellular channels from 1.5-2 nm in diameter. Functions: 1. Essential for multicellular life.2. Contact between cells that mediate the exchange of small molecules.3. It may act as an ion condructor.*Note: The gap junctions of vertebrates & vertebrates are similar in both structure & function.--> But the most common are composed of the connexin family. Gap junctions are seen as patches of varying size.
The gap reflects areas of 2 membranes connected by HEXAGONALTUBES called (CONNEXINS)
A connexin is formed from 6 connexin molecules. When seen by electron microscope:
1.the tonofilaments and the desomsomes acts as a supporting system for the epithelium.
2.help to resist shearing forces found in the simple stratified squamous epithelium . Functions: Adherens junctions are composed of the following proteins:
p120 (sometimes called delta catenin)