Browsing by Subject "ADHERENS JUNCTIONS"

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  • Wickstroem, Sara A.; Niessen, Carien M. (2018)
    Biological patterns emerge through specialization of genetically identical cells to take up distinct fates according to their position within the organism. How initial symmetry is broken to give rise to these patterns remains an intriguing open question. Several theories of patterning have been proposed, most prominently Turing's reaction-diffusion model of a slowly diffusing activator and a fast diffusing inhibitor generating periodic patterns. Although these reaction-diffusion systems can generate diverse patterns, it is becoming increasingly evident that cell shape and tension anisotropies, mediated via cell-cell and/or cell-matrix contacts, also facilitate symmetry breaking and subsequent self-organized tissue patterning. This review will highlight recent studies that implicate local changes in adhesion and/or tension as key drivers of cell rearrangements. We will also discuss recent studies on the role of cadherin and integrin adhesive receptors in mediating and responding to local tissue tension asymmetries to coordinate cell fate, position and behavior essential for tissue self-organization and maintenance.
  • Kovac, Bianca; Makela, Tomi P.; Vallenius, Tea (2018)
    The controlled formation and stabilization of E-cadherin-based adhesions is vital for epithelial integrity. This requires co-operation between the E-cadherin-based adhesions and the associated actin cytoskeleton. In cancer, this co-operation often fails, predisposing cells to migration through molecular mechanisms that have only been partially characterized. Here, we demonstrate that the actin filament cross-linker alpha-actinin-1 is frequently increased in human breast cancer. In mammary epithelial cells, the increased alpha-actinin-1 levels promote cell migration and induce disorganized acini-like structures in Matrigel. This is accompanied by a major reorganization of the actin cytoskeleton and the associated E-cadherin-based adhesions. Increased expression of alpha-actinin-1 is particularly noted in basal-like breast cancer cell lines, and in breast cancer patients it associates with poor prognosis in basal-like subtypes. Downregulation of alpha-actinin-1 in E-cadherin expressing basal-like breast cancer cells demonstrate that alpha-actinin-1-assembled actin fibers destabilize E-cadherin-based adhesions. Taken together, these results indicate that increased alpha-actinin-1 expression destabilizes E-cadherin-based adhesions, which is likely to promote the migratory potential of breast cancer cells. Furthermore, our results identify alpha-actinin-1 as a candidate prognostic biomarker in basal-like breast cancer.
  • Huang, Yunxian; Gui, Jinghua; Myllymäki, Satu-Marja; Roy, Kallol; Tonissoo, Tambet; Mikkola, Marja L.; Shimmi, Osamu (2022)
    Epithelial homeostasis is an emergent property of both physical and biochemical signals emanating from neighboring cells and across tissue. A recent study reveals that Scribble, an apico-basal polarity determinant, cooperates with alpha-Catenin, an adherens junction component, to regulate tissue homeostasis in the Drosophila wing imaginal disc. However, it remains to be addressed whether similar mechanisms are utilized in vertebrates. In this study, we first address how alpha-Catenin cooperates with Scribble to regulate epithelial homeostasis and growth in mammalian cells. Our data show that alpha-Catenin and Scribble interact physically in mammalian cells. We then found that both alpha-Catenin and Scribble are required for regulating nuclear translocation of YAP, an effector of the Hippo signaling pathway. Furthermore, ectopic Scribble suffices to suppress YAP in an alpha-Catenin-dependent manner. Then, to test our hypothesis that Scribble amounts impact epithelial growth, we use the Drosophila wing imaginal disc. We show that Scribble expression is complementary to Yorkie signal, the Drosophila ortholog of YAP. Ectopic expression of full-length Scribble or Scribble Leucine Rich Region (LRR):alpha-Catenin chimera sufficiently down-regulates Yorkie signal, leading to smaller wing size. Moreover, Scribble LRR:alpha-Catenin chimera rescues scribble mutant clones in the wing imaginal disc to maintain tissue homeostasis. Taken together, our studies suggest that the association of cell polarity component Scribble with alpha-Catenin plays a conserved role in epithelial homeostasis and growth.
  • Hildebrand, Sebastian; Hultin, Sara; Subramani, Aravindh; Petropoulos, Sophie; Zhang, Yuanyuan; Cao, Xiaofang; Mpindi, John; Kallioniemi, Olli; Johansson, Staffan; Majumdar, Arindam; Lanner, Fredrik; Holmgren, Lars (2017)
    Epithelial cells connect via cell-cell junctions to form sheets of cells with separate cellular compartments. These cellular connections are essential for the generation of cellular forms and shapes consistent with organ function. Tissue modulation is dependent on the fine-tuning of mechanical forces that are transmitted in part through the actin connection to E-cadherin as well as other components in the adherens junctions. In this report we show that p100 amotL2 forms a complex with E-cadherin that associates with radial actin filaments connecting cells over multiple layers. Genetic inactivation or depletion of amotL2 in epithelial cells in vitro or zebrafish and mouse in vivo, resulted in the loss of contractile actin filaments and perturbed epithelial packing geometry. We further showed that AMOTL2 mRNA and protein was expressed in the trophectoderm of human and mouse blastocysts. Genetic inactivation of amotL2 did not affect cellular differentiation but blocked hatching of the blastocysts from the zona pellucida. These results were mimicked by treatment with the myosin II inhibitor blebbistatin. We propose that the tension generated by the E-cadherin/AmotL2/actin filaments plays a crucial role in developmental processes such as epithelial geometrical packing as well as generation of forces required for blastocyst hatching.