Cleavage of DFNA5 by caspase-3 during apoptosis mediates progression to secondary necrotic/pyroptotic cell death

TLDR

Apoptosis is driven by effector caspases 3, 6, and 7, and when apoptotic cells are not cleared they can progress to a lytic, inflammatory secondary necrosis, though the underlying mechanism remains unknown. The authors propose that DFNA5‑induced secondary necrosis and GSDMD‑mediated pyroptosis represent programmed necrotic pathways dependent on caspase activation. They demonstrate that caspase‑3 cleaves DFNA5 at Asp270 to generate a membrane‑targeting DFNA5‑N fragment that drives secondary necrosis/pyroptosis, and that loss of DFNA5 prevents this progression, establishing DFNA5 as a key regulator and revealing the molecular mechanism of secondary necrosis.

Abstract

Abstract Apoptosis is a genetically regulated cell suicide programme mediated by activation of the effector caspases 3, 6 and 7. If apoptotic cells are not scavenged, they progress to a lytic and inflammatory phase called secondary necrosis. The mechanism by which this occurs is unknown. Here we show that caspase-3 cleaves the GSDMD-related protein DFNA5 after Asp270 to generate a necrotic DFNA5-N fragment that targets the plasma membrane to induce secondary necrosis/pyroptosis. Cells that express DFNA5 progress to secondary necrosis, when stimulated with apoptotic triggers such as etoposide or vesicular stomatitis virus infection, but disassemble into small apoptotic bodies when DFNA5 is deleted. Our findings identify DFNA5 as a central molecule that regulates apoptotic cell disassembly and progression to secondary necrosis, and provide a molecular mechanism for secondary necrosis. Because DFNA5-induced secondary necrosis and GSDMD-induced pyroptosis are dependent on caspase activation, we propose that they are forms of programmed necrosis.