Epithelium Flashcards
3 types of anchoring junctions
Adherens junctions/ zonula adherens/intermediate junction/belt desmosomes
Desmosomes /macula adherens
Hemidesmosomes
Examples of Occluding junctions
Tight junctions /zonula occludens
Example of channel forming junction
Gap junction /Nexus
Example of signal relaying junctions
Synapses
4 types of cell-cell junctions
Anchoring junctions
Occluding junctions
Channel forming junctions
Signal relaying junctions
Anchoring junctions used 2 key types of transmembrane adhesion proteins
Cadherins
Integrins
Cadherins
Ca2+ dependent
Assemble complex of proteins that tether to actin filaments of cytoskeleton
What builds intrinsic strength in cells
Actin cytoskeletons linked together
Desmosomes
Bind to plaques of intracellular anchor proteins & interact through their extracellular domains to hold adjacent membranes together - Ca2+ dependent
Types of catenins and what they associate with
α, β & p120 catenins & E cadherin in adherens junctions
Plakoglobin & plakophilin catenins & desmosomal cadherins
How is Wnt signalling pathway activated?
Wnt binds to its cell surface receptor - Frizzled
What is the target gene for β catenin and what happens?
Myc
Enters nucleus, displaces Groucho & binds to LEF1/TCF & acts as coactivator for c-Myc
3 examples of plakins
Desmoplakin - links IF to cadherin complex in desmosomes
Plectin - found in hemidesmosomes, costameres & throughout epithelial & muscle cells
Dystonin/BP230/BPAG-1 - links IF to hemidesmosomes
Hemidesmosomes
Form junctions between epidermal cells & ECM
Pemphigus Bullous
Attacking desmosomes
IgG autoantibodies bind to keratinocyte desmosomes & desmosome free areas of keratinocyte cell membrane
Acantholysis
Bullous pemphigoid
Attack hemidesmosomes due to presence of autoantibodies specific for BP230 & BP180 antigens
Acantholysis
3 types of Epidermolysis Bullosa and their 2 common features
Non inflammatory disorders that cause blistering & marked mechanical fragility of skin
EB Simplex
EB Junctional
EB dystrophic
Epidermolysis Bullosa Simplex
Caused by mutations in KRT5 & KRT14
Epidermolysis Bullosa Junctional
Blistering occurs w/in basal lamina
Mutations in genes for laminin 332, BP180, integrin & pectin
Epidermolysis Bullosa Dystrophic
Defects in gene encoding BP180
Components of tight junctions
Transmembrane proteins - occludins, claudins, JAMs
Peripheral proteins - ZO-1, ZO-2, ZO-3
3 Main functions of tight junctions
Signalling
Barrier
Fence
During initial assembly of junctions, JAM recruits _______ to establish ______
PAR3-PAR6-aPKC
Border between apical & lateral domains
