Synaptopodin couples epithelial contractility to α-actinin-4-dependent junction maturation.
The epithelial junction experiences mechanical force exerted by endogenous actomyosin activities and from interactions with neighboring cells. We hypothesize that tension generated at cell-cell adhesive contacts contributes to the maturation and assembly of the junctional complex. To test our hypothesis, we used a hydraulic apparatus that can apply mechanical force to intercellular junction in a confluent monolayer of cells. We found that mechanical force induces α-actinin-4 and actin accumulation at the cell junction in a time- and tension-dependent manner during junction development. Intercellular tension also induces α-actinin-4-dependent recruitment of vinculin to the cell junction. In addition, we have identified a tension-sensitive upstream regulator of α-actinin-4 as synaptopodin. Synaptopodin forms a complex containing α-actinin-4 and β-catenin and interacts with myosin II, indicating that it can physically link adhesion molecules to the cellular contractile apparatus. Synaptopodin depletion prevents junctional accumulation of α-actinin-4, vinculin, and actin. Knockdown of synaptopodin and α-actinin-4 decreases the strength of cell-cell adhesion, reduces the monolayer permeability barrier, and compromises cellular contractility. Our findings underscore the complexity of junction development and implicate a control process via tension-induced sequential incorporation of junctional components.
Program in Global Public Health, University of Illinois, Urbana-Champaign, Champaign, IL 61801.
Nivetha
N
Kannan
Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Champaign, IL 61801 vtang@illinois.edu.
Vivian W
VW
Tang
D008841:Actin Cytoskeleton / Q000378:metabolism; D000185:Actinin / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism; D022005:Adherens Junctions / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion / Q000235:genetics / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002460:Cell Line; D004285:Dogs; D004847:Epithelial Cells / Q000502:physiology*; D006801:Humans; D061985:Madin Darby Canine Kidney Cells; D040542:Mechanotransduction, Cellular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism; D024462:Myosin Type II / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016708:Synaptophysin / Q000235:genetics / Q000378:metabolism*; D013718:Tensile Strength; D016596:Vinculin / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism
D000199:Actins; D015815:Cell Adhesion Molecules; D046912:Multiprotein Complexes; D016708:Synaptophysin; D051176:beta Catenin; D000185:Actinin; D016596:Vinculin; D000205:Actomyosin; D024462:Myosin Type II