TAT-RasGAP kills cells by targeting inner-leaflet-enriched phospholipids.

TAT-RasGAP is a cell-penetrating peptide-based construct with anticancer and antimicrobial activities. This peptide kills a subset of cancer cells in a manner that does not involve known programmed cell death pathways. Here we have elucidated the mode of action allowing TAT-RasGAP to kill cells. This peptide binds and disrupts artificial membranes containing lipids typically enriched in the inner leaflet of the plasma membrane, such as phosphatidylinositol-bisphosphate (PIP) and phosphatidylserine (PS). Decreasing the amounts of PIP in cells renders them more resistant to TAT-RasGAP, while reducing the ability of cells to repair their plasma membrane makes them more sensitive to the peptide. The W317A TAT-RasGAP point mutant, known to have impaired killing activities, has reduced abilities to bind and permeabilize PIP- and PS-containing membranes and to translocate through biomembranes, presumably because of a higher propensity to adopt an α-helical state. This work shows that TAT-RasGAP kills cells via a form of necrosis that relies on the physical disruption of the plasma membrane once the peptide targets specific phospholipids found on the cytosolic side of the plasma membrane.