Karyoptosis mediates cell death and neurodegeneration upon proteotoxic stress.

Neurodegenerative diseases are frequently associated with proteotoxic stress linked to disease specific proteins. The autophagy(definition)-lysosome system provides essential control of proteotoxic stress and its failure can lead to initiation of apoptosis. However, in aging and neurodegenerative diseases apoptosis is insufficient to account for all neuronal death, and several different cell death types have been reported in these contexts. Here we show that karyoptosis, a distinct form of cell death, can be induced by proteotoxic stress and then develops through nuclear degeneration and cellular expulsion of nuclear material. We establish that karyoptosis is regulated by the p38 kinase signalling pathway, which controls stability of the nuclear lamina protein LaminB1 via direct phosphorylation. We demonstrate that karyoptosis affects neurons in models of amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) pathology. Finally, we identify karyoptotic features in post-mortem frontal cortex of FTD and Alzheimer's disease (AD) patients. Together these findings characterise a form of cell death directly linked to proteotoxic stress and nuclear lamina stability that is associated with neurodegeneration.