So actin is pulling at least double duty here its causing the

So actin is pulling at least double duty here its

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So actin is pulling (at least) double duty here: it's causing the extension/protrusion of the cells, and it acts to communicate the tension between the cell-matrix adhesion sites throughout the cell. It is important to remember that although the figure shows the focal adhesions to be on the bottom, this is only true in vitro . In vivo , cells are surrounded in three dimensions and focal adhesions are on all sides. Try to picture this three- dimensional cell environment from the cell's point of view. CELLS CONNECT TO EACH OTHER: Cell-Cell Cohesion So we've seen how cells are attached to the extracellular matrix; how they can reach out filopodia to sense their environment; and how they can move along the matrix by extending lamellipodia, and retracting the attachment on the other side of the cell. But cells do not exist and travel in isolation. They are surrounded by other cells, to which they are intimately connected. The extracellular matrix to which they are attached lies between each cell, and direct cell-to- cell contacts protrude through this matrix. Note in this figure that the cell-cell contacts – mediated by direct interaction of cell-surface molecules leads to direct molecular connection between the cytoskeletons in the two cells. Therefore the cytoskeleton links adjacent cells and the extracellular matrix. ADHERENS JUNCTIONS are formed by Cell-Surface CADHERINS. There are multiple types of cadherins with similar structure. The type expressed on vascular endothelial cells is called VE-Cadherin. The extracelluar domains of cadherins bind to each other in an anti-parallel orientation; this means that a cadherin molecule binds to another but on a different (neighboring) cell. Cadherins Link To The Cytoskeleton Through Catenins. Just like talin and vinculin for focal adhesions, catenins serve as the adapters for adherens junctions to the actin cytoskeleton. Catenins are regulated by the Wnt pathway , which you have covered earlier in this course. Whether in vivo or in vitro , cadherins and catenins are localized to cell-cell junctions, as we can see from the immunofluorescent images below. Here we give examples of endothelial cells, but other cell types have similar arrangements. beta-Catenin expression (green) in endothelial cells in vitro (left) and in blood vessels (right)
Molecules and Cells 2015 – Lecture notes – Dynamic Multicellular Behavior (Mac Gabhann) 19 Alberts 4 th Ed Figure 19-29 Alberts 4 th Ed Figure 19-9 beta-Catenin Cadherin Endothelial cells in vitro express VE-Cadherin (green) at the cell-cell junctions _1.jpg Endothelial cells in cylindrical blood vessels in vivo express VE-Cadherin at cell-cell junctions . f4/medium
Molecules and Cells 2015 – Lecture notes – Dynamic Multicellular Behavior (Mac Gabhann) 20 CELLS CAN SENSE SIGNALS FROM OUTSIDE AT THEIR SURFACE

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