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
- function
- structural support
- couples intermediate filament to plasma membrane in adjacent cells
- autoantibodies target desmoglein component of desmosomes
Gap Junction
- Gap junction
- location
- between adjacent epithelial cells
- function
- forms channel for electrical and chemical communication between adjacent cells
- location
- 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
- location