Cell Junctions

Cell Junctions

tight junctions
1. semi fusion
  1. local connections between plasma mem
2. stop leakage
3. aka occulding junctions
4. leaky
  1. paracellular transport
5. continuous apical band
6. freeze fracture - structure
7. Claudin
  1. link to actin
    1. anchoring
      1. internal support
8. structure
  1. proteins through bilayer
    1. claudin
    2. occludin
    3. link to actin
Gap junctions
1. dont semi fuse
  1. connect cytoplasms
2. low resistant channels/pores
3. belts
  1. heart/smooth muscle/neurons
  2. belt desmosomes
    1. actin associated and motor protein
      1. contractile actin rings tighten/slacken
        reshaping tissues
        invagination forming neural tube
  3. multiple cadherins
4. electrochemical AP move through
  1. charged ions
  2. IP3,ATP, AA, cAMP intracell messengers
    1. no proteins mRNA
5. structure
  1. aqueous pore
  2. 2 connexons line
    1. made of 6 connexins/innexins
    2. hetero/homomeric
    3. heter/homotypic
  3. 1000 mw fits through
  4. 1.5nm diametre
  5. intracellular channel
6. opening/closing
  1. pH, Ca2+, signalling mols
  2. retina
    1. gap junctions in neurons leaks dye
  3. closing
    1. dopamine
    2. Ca2+
      1. too much is toxic
importance of junctions
1. Pemphigus
  1. autoimmune disease
    1. skin blisters
      1. desmoglein foreign (cadherin)
        weakened junctions
Desmosomes
1. homophilic interactions
2. with intermediate filaments
  1. and cadherins
Hemidesmosomes
1. to basal lamina
  1. laminin (integrin)
    1. focal adhesions with extracellular matrix
2. with actin
cell adhesion molecules
1. between cells
  1. immunoglobins - weak
    1. non Ca2+/Mg2+ dependent
  2. cadherin - strong
Adherins junctions
1. adhesion molecules on cell surface
2. calcium dependant cadherin
  1. homophillic interactions
  2. dimers
  3. to anchor proteins
    1. to actin filaments
      1. catenins - molecules that express cadherin
      2. bundles
        adhesion belts
3. E type = embryonic/epithelial
cytoplasmic plaque
1. intracellular anchor proteins
2. keratin filaments
  1. desmosomes
    1. anchored to cytoplasmic plaque

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	Created by devans1 almost 11 years ago