Apoptosis Explained: p53 Activation, Cytochrome c Release, the Apoptosome, and the Caspase Cascade скачать в хорошем качестве

Apoptosis Explained: p53 Activation, Cytochrome c Release, the Apoptosome, and the Caspase Cascade

This video walks through the molecular sequence that drives apoptosis (programmed cell death), starting with the key regulator p53. Under normal conditions, p53 is continuously produced but kept low because it is ubiquitinated and degraded by the proteasome. When a cell receives stress signals, either intrinsic (for example DNA damage) or extrinsic (death receptor signalling), kinases phosphorylate p53. This phosphorylation changes p53’s shape, prevents its ubiquitination, and allows p53 to accumulate and enter the nucleus to switch on pro-apoptotic genes. A major downstream step is the production of pore-forming proteins that permeabilise the mitochondrial membrane. This releases cytochrome c (and adaptor proteins) into the cytosol, where they assemble into the apoptosome (described as a “ninja star” complex). The apoptosome recruits inactive caspase zymogens and activates them through proximity-driven cleavage, triggering a caspase activation cascade. This cascade amplifies the signal dramatically, activating enzymes that fragment DNA into manageable pieces and proteases that dismantle cellular proteins, including the cytoskeleton. The breakdown of the cytoskeleton, together with changes in ion and water movement, drives membrane blebbing and the packaging of cell contents into apoptotic bodies for clearance.