What triggers the cleavage of nuclear lamins during apoptosis?

The cleavage of nuclear lamins during apoptosis is primarily triggered by executioner caspases. These are a class of cysteine proteases that play a crucial role in the apoptotic process. Once apoptosis is initiated, executioner caspases become activated and are responsible for the dismantling of cellular structures and the execution of the death program.

Specifically, executioner caspases target various cellular substrates, including nuclear lamins, which are structural proteins that provide integrity to the nuclear envelope. The cleavage of lamins leads to the disassembly of the nuclear envelope, a hallmark of the early stages of apoptosis known as nuclear shrinkage and ultimately contributes to the overall morphological changes observed during programmed cell death.

While nucleases may be involved in degrading DNA during apoptosis, they are not directly responsible for lamin cleavage. Initiator caspases, on the other hand, are involved early in the apoptotic signaling cascade but do not directly cleave effector proteins like lamins. Regulatory proteins may help control the apoptotic process, but they do not cleave lamins directly. Therefore, executioner caspases are the key players in the specific cleavage of nuclear lamins, leading to the characteristic features of apoptosis.