Insights into the Molecular Mechanism Underlying tBID-Triggered Cell Death Probed by In Situ Raman Spectroscopy

The truncated BID (tBID) protein is crucially important for apoptosis, and recent studies have shown that it can directly trigger cell death. However, the underlying molecular mechanisms are poorly understood. Herein, we present the molecular details of tBID–phospholipid interactions and their correlations with mitochondrial and lysosomal membrane permeabilization during apoptosis. Using Raman spectroscopy, we find that tBID disrupts the conformational order in alkyl chains by selectively binding to phosphatidylethanolamine, cardiolipin (CL), and phosphatidic acid (PA). Our results reveal that tBID undergoes significant conformational changes upon phospholipid binding, generating a redox center that mediates reactive oxygen species (ROS) formation, which, in turn, induces peroxidation of unsaturated phospholipids. These results unveil the key mechanism underlying tBID-induced membrane permeabilization and cytochrome c release from the mitochondria. This study provides novel insights into how tBID mediates apoptosis through crosstalk between mitochondria and lysosomes and paves the way for the development of novel anticancer treatments.