An Old Death with a New Twist: The Roles of Intrinsically Disordered Proteins and Phase Separation in Cellular Suicide

Programmed cell death (PCD) is a set of tightly controlled biological pathways that eliminate obsolete or damaged cells to preserve tissue homeostasis and support development. Despite their mechanistic variations, all PCD pathways share three fundamental characteristics: a genetic basis, stringent regulation, and an active requirement for energy to drive cellular self-destruction. While PCD signaling pathways are heavily studied, their precise spatial and temporal organization remains elusive. Intrinsically disordered proteins (IDPs), liquid-liquid phase separation (LLPS), and membraneless organelles (MLOs) have emerged as fundamental principles for cellular organization, enabling rapid stress adaptation and signal integration. This review provides a brief overview of the complexity of PCD pathways and summarizes the roles of IDPs, LLPS, and MLOs in PCD regulation and execution. This biophysical perspective challenges the view of cell death as a fatalistic, binary outcome, reimagining cellular suicide not as something 'written in stone', but as a highly regulated continuum of decreasing vitality.