A two-tiered mechanism for stabilization and immobilization of E-cadherin
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Transcript of A two-tiered mechanism for stabilization and immobilization of E-cadherin
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A two-tiered mechanism for stabilization and immobilization of
E-cadherin
Matthiue Cavey, Matteo Rauzi, Pierre-François Lenne & Thomas Lecuit
Presented by Shig3/5/10
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Background: E-cadherinCadherin – calcium dependent adhesion molecules that mediate cell-cell interactions
E-cadherin – epithelial cadherin
Homo-E-cad – E-cad homodimer that localizes at SAJs
SAJ – spot adherens junction
Role in development: – spatio-temporal cadherin levels change
Role in adult – ie: intestine and bloodstream barrier
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Homophilic E-cadherin clusters in stable microdomains
FRAP
E-cad-GFP fusion
Figure 1: FRAP of E-cad-GFP
Bright region Low-intensity region
Also demonstrated with E-cad-EosFPPhotoconvert -> no exchange w/neighbors Bright SAJ
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Two dynamically distinct actin populations
Figure 2: Didn’t observe depolymerization of all F-actin with latrunculin-A (Lat-A)
Actin patches underlie SAJ stability: SAJs dimmer in Lat-A treated embryos.
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α-Cat is not essential for homo-E-cad stability
β-catenin
α-catenin
E-cad
F-actinTraditional View
Knockdown α-Cat by RNAi
No detectible α-Cat in SAJs
E-cad-β-Cat spots still colocalize with F-actin
Figure 2: α-Cat not required to retain Lat-A resistant F-actin patches at SAJs
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A tensile actin network controls mobility of SAJs
Lat-A: prevents actin polymerization
RNAi
Figure 3
Bitesize: organizes actin filaments at cell junctions through Moesin (F-actin binding protein)
Reorganize actin network:increase mobility of SAJs.
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A tensile actin network controls mobility of SAJs
DiaCA: Diaphanous – promotes unbranched actin elongation
myrWasp: promotes cortical actin branching
Rok inhibitor: removes myosin-II motors within the cortical actin network
Figure 3
Fortify actin network:decrease mobility of SAJs.
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α-Cat mediates tethering ofhomo-E-cad by cortical actin
Figure 3: α-Cat RNAi increases SAJ mobility
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α-Cat mediates tethering ofhomo-E-cad by cortical actin
Figure 4: Nano-joule ablation to sever actin networkUncaged fluorescein
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Model: two-tiered stabilization and immobilization of E-cadherin
Stability:
Mobility:
homo-E-cad at SAJs is stable
independent of α-catenin
E-Cad-β-Cat-F-actin structural units
linker between E-Cad-β-Cat and actin?
α-catenin links E-cad to actin
actin rearrangement delocalizes E-cad
factors acting on actin effect SAJ mobility
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Future directions
• Calcium necessary for E-cad rigidity and adhesion– calcium regulation during development
• More linkers between SAJs and actin?– genetic screen
• Role of microtubules and associated proteins• Better characterization of nano-scissors