Figure 7.

A hypothesized model of a possible role for vinculin in membrane cortical tension and compression of the Z-disk. In this model, vinculin maintains tension in the cortical cytoskeleton which compresses the Z-disk. When vinculin is deleted, the stiffness and force of the protein complex at the costamere (long dashed downwardarrows in panels A and B) is decreased (represented by shorter dashed arrows in panels C and D), which in turn leads to a decrease in the cortical tension (represented by shorter horizontal solid arrows in the cortical cytoskeleton in panels C and D), corresponding to lower AFM indentation force (open arrows). This decrease in cortical tension allows for the Z-disk to expand (owing to reduced compression of the Z-disk balanced by the reduced cortical tension). The expansion of the Z-disk leads to a larger lattice spacing.