Intracellular apoptotic machinery

The intracellular apoptotic machinery is a highly regulated network of proteins responsible for executing programmed cell death (apoptosis), a process vital for tissue homeostasis and the removal of damaged cells (PubMed, 2001). This machinery is primarily organized into two converging pathways: the intrinsic (mitochondrial) pathway, which is regulated by the Bcl-2 family of proteins, and the extrinsic (death receptor) pathway, initiated by cell surface receptors such as Fas and TRAIL (PMC, 2014; PMC, 2020). At the core of this system are caspases, a family of cysteine proteases that act as the executioners of the cell by cleaving specific structural and functional proteins (Science Alert, 2011). In cancer, the machinery is frequently suppressed through the overexpression of anti-apoptotic proteins like Bcl-2 or XIAP, or via mutations in tumor suppressors like p53, allowing malignant cells to survive and resist treatment (PMC, 2016). Conversely, excessive activation of these pathways contributes to the pathological cell loss seen in neurodegenerative and cardiovascular diseases (PubMed, 2001). Therapeutic strategies focus on either reactivating this machinery in cancer cells using BH3 mimetics (e.g., venetoclax) and Smac mimetics, or inhibiting it in degenerative conditions using caspase inhibitors (PMC, 2020; PMC, 2010). The clinical success of targeting this machinery depends on achieving selectivity for diseased cells to avoid systemic toxicity (PMC, 2020). Monitoring biomarkers such as cleaved caspase-3 or Bcl-2 expression levels is essential for assessing the efficacy of these targeted therapies (PMC, 2016).

Other names

Programmed cell death machineryCore apoptotic machineryApoptotic signaling pathwayIntrinsic and extrinsic apoptotic pathways

Modulation of the balance between pro-apoptotic and anti-apoptotic proteins, direct activation of executioner caspases, or inhibition of endogenous apoptosis inhibitors to induce or prevent programmed cell death.