Apoptotic Signaling Mechanisms in Cell Death

Apoptosis is a highly regulated form of programmed cell death essential for embryonic development, tissue homeostasis and elimination of damaged or infected cells. Two principal signalling cascades govern apoptotic initiation: the intrinsic pathway, driven by mitochondrial outer membrane permeabilisation and release of cytochrome c, and the extrinsic pathway, triggered by activation of death receptors such as Fas or tumour necrosis factor receptor. Both routes converge on a cascade of cysteine proteases known as caspases, with initiator caspases (for example caspase-8 or caspase-9) activating downstream executioner caspases (notably caspase-3, ‑6 and ‑7). Executioner caspases cleave a wide array of structural and regulatory substrates, leading to characteristic morphological changes including cell shrinkage, chromatin condensation and membrane blebbing. Recent work has uncovered an amplification step within the nucleus, revealing that nuclear substrate cleavage can feed back to reinforce mitochondrial and cytosolic death signals. Dysregulation of apoptotic signalling underlies numerous pathologies—from cancer, where cell death is thwarted, to neurodegenerative disorders, where excessive apoptosis contributes to tissue loss. Therapeutic modulation of key nodes in this network, including BCL-2 family interactions, caspase activation and inhibitors of apoptosis proteins, holds promise for targeted interventions in diverse disease contexts.

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Apoptotic Signaling Mechanisms in Cell Death publication trend

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Technical terms

Apoptosis: A form of programmed cell death involving orderly cellular dismantling to maintain organismal health and homeostasis.

Caspases: A family of cysteine-dependent aspartate-specific proteases that orchestrate the initiation and execution phases of apoptosis.

Intrinsic pathway: Apoptotic signalling initiated by mitochondrial outer membrane permeabilisation and release of pro-apoptotic factors such as cytochrome c.

Extrinsic pathway: Apoptotic signalling triggered by ligand binding to death receptors, leading to assembly of death-inducing signalling complexes.

Mitochondrial outer membrane permeabilisation (MOMP): The process by which pro-apoptotic BCL-2 family proteins form pores in the mitochondrial membrane, releasing apoptogenic factors.

Proteome-wide cellular thermal shift assay (CETSA): A method to assess protein stability and interactions across the proteome by measuring thermal denaturation profiles.

Nuclear proteases: Enzymes resident in the nucleus that cleave specific substrates to regulate chromatin structure and apoptotic progression.

References

1. Proteome-wide CETSA reveals new step in apoptosis control. Trends in Cell Biology (2024).
2. The Mechanisms of Regulated Cell Death: Structural and Functional Proteomic Pathways Induced or Inhibited by a Specific Protein—A Narrative Review. Proteomes (2024).
3. New Perspectives on the Role of Nuclear Proteases in Cell Death Pathways. Biology (2023).