cell junctions

cell junctions

1. transient cell-cell junctions

   • these are temporary cell-cell junctions
   • when a pathogen is recognized in a tissue, macrophages release cytokines/chemokines into the blood, to the cell with the pathogen. these cells express selectin which binds to leukocytes. this allows the leukocytes to enter the pathogen containing cells

2. stable cell-cell junctions

   • tight junctions
     • made of transmembrane proteins: occludins
     • function: holds cells together, barrier and stops integral proteins moving from the apical surface
     • example: epithelial cells of the small intestines, just under the microvilli
   • anchoring junctions
     • actin-associated junctions
       • belt desmosome
         • cell-cell junction
         • made by proteins: cadherins and catinine
       • focal adhesion
         • cell-ECM junction
         • link to the ECM made by integrin and proteoglycans
     • intermediate filament associated junctions
       • hemidesmosome
         • function: stabilizes the cell
         • cell-lamina basal
       • spot desmosome
         • proteins: cadherins, catenin, cytoplasmic plaque and intermediate fil.
         • cell-cell
         • function: stablize the cells and makes them resistant to mechanical injuries
   • communication junctions: Gap junctions
     • cell-cell
     • communication through a channel which is formed by 6 connexin transmembrane proteins

3. diseases associated with junctions

   • pemphigus (bullosa pemphigoid)
     • autoimmune disease
     • linked with spot and hemidesmosome
     • the body makes antibodies to against specific cadherins which weakens the connections between epithelial cells which causes blisters