Apoptosis is a type of programmed cell death which cells undergo to maintain tissue homeostasis. However, when epithelial cells undergo apoptosis, one major challenge faced by the tissue is removal of corpses to maintain the integrity. inefficient removal of an apoptotic body can invoke an inflammatory response or entry of microbes in an organ. Hence, epithelia remove the dead cell by one of the two mechanisms: phagocytosis or apical (apoptotic) extrusion. Apoptotic extrusion is stimulated by hypercontractility of a dead cell. This is further sensed by neighbours of the dying cell, leading to the physical expulsion of an apoptotic cell in an apical direction.
The role of adherens junction and actomyosin machinery in apoptotic extrusion has been widely studied. But the role of another cell junction complex which provides mechanical strength to epithelia, the desmosome, is largely unexplored. Here, we provide evidence that desmoplakin (DP), a part of the demosomal complex, supports the neighbours of the dying cell in driving apoptotic extrusion. While investigating the mechanism of this role, we found that DP plays a role in the activation of RhoA when epithelial cells are subjected to force.
Finally, these observations suggest that desmosomes work in concert with adherens junctions to maintain epithelial integrity when cells undergo apoptosis or are subjected to physical forces.