Updated: 4/3/2020

Epithelial Cell Junctions

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Overview
 

 
Snapshot
  • A 40-year-old woman presents with a pruritic rash of 2 weeks duration. She reports a persistent rash over her extremities with very itchy blisters that do not break easily. On physical exam, she has multiple 1-5 cm tense bullae on her abdomen and arms. Skin biopsy with direct immunofluorescence shows linear pattern of IgG and C3 deposits along the epidermal-dermal junction. (Bullous pemphigoid)
Tight Junction
  • Tight junction
    • also known as zonula occludens
    • location
      • between adjacent epithelial cells
    • composition
      • claudins
      • occludins
    • function
      • diffusion barrier between adjacent cells
      • prevents paracellular movement of solutes
      • maintains physiochemical separation of tissue compartments
Adherens Junction
  • Adherens junction
    • also known as belt desmosome, zonula adherens, and intermediate junctions
    • location
      • between adjacent epithelial cells
    • composition
      • e-cadherin
    • function
      • forms a belt that connects actin cytoskeletons to plasma membrane
      • actin filaments connect with E-cadherin
        • cadherins are Ca2+-dependent adhesion proteins
      • loss of E-cadherins promote metastasis
Desmosome
  • Desmosome
    • also known as spot desmosome and macula adherens
    • location
      • between adjacent epithelial cells
    • composition
      • desmoplakin
      • desmoglein 
        • connects keratinocytes in stratum spinosum
      • desmocollin
    • function
      • structural support
      • couples intermediate filament to plasma membrane in adjacent cells
    • diseases
      • pemphigus vulgaris
        • autoantibodies target desmoglein component of desmosomes
Gap Junction
  • Gap junction
    • location
      • between adjacent epithelial cells
    • composition
      • connexons with central channel 
    • function
      • forms channel for electrical and chemical communication between adjacent cells
      • permits exchange of ions, regulatory molecules, and small metabolites through pores
Hemidesmosome
  • Hemidesmosome
    • location
      • between epithelial cell and basement membrane
    • composition
      • integrin
    • function
      • connects epithelial cells to underlying basement membrane
      • integrins bind to laminin-5 and type IV collagen, attaching epithelial cell to extracellular matrix
    • diseases
      • bullous pemphigoid
        • autoantibodies target hemidesmosome
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Questions (3)
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(M1.MK.15.70) A scientist is studying the anatomy and function of bone growth. He is able to create a cell line of osteocytes with a mutation that prevents the osteocytes from exchanging nutrients and waste products within neighboring lamellae. This mutation most likely affected which of the following cell structures? Tested Concept

QID: 106483
1

Gap junctions

84%

(130/155)

2

Plasma membrane

5%

(8/155)

3

Kinesin

1%

(1/155)

4

Dynein

3%

(4/155)

5

Endoplasmic reticulum

4%

(6/155)

M 1 E

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