Apoptosis Pathway Protein Set

These five proteins—tumor protein p53 (TP53), cyclin-dependent kinase inhibitor 1A (p21, CDKN1A), Bcl-2-associated X protein (Bax), B-cell lymphoma 2 protein (Bcl-2), and cleaved caspase-3—are central to the intrinsic (mitochondrial) apoptosis pathway and the regulation of cell cycle arrest in response to cellular stress or DNA damage. Upon activation, p53 acts as a transcription factor, upregulating p21 (leading to cell cycle arrest) and Bax (promoting apoptosis). Bcl-2 inhibits apoptosis by impeding Bax function. Upon sufficient pro-apoptotic signaling, mitochondrial outer membrane permeabilization (by Bax) permits cytochrome c release, triggering the formation of the apoptosome and activating caspase-9, which then activates caspase-3; cleaved caspase-3 then orchestrates apoptotic cell demise[1][2][3][4]. These molecules serve as both biomarkers and therapeutic targets in cancer and other diseases involving cell death dysregulation.

Other names

TP53CDKN1ABAXBCL2Caspase-3 (cleaved)

Activation of p53 leads to cell cycle arrest (via p21) or apoptosis (via Bax, PUMA, Noxa). Bax (pro-apoptotic) promotes mitochondrial outer membrane permeabilization, releasing cytochrome c, which activates caspase-9 and downstream cleaved caspase-3[1][2][3][4]. Bcl-2 (anti-apoptotic) blocks Bax/Bak-mediated mitochondrial permeabilization, opposing apoptosis[1][3]. Cleaved caspase-3 executes apoptosis by cleaving cellular substrates. Many anti-cancer drugs induce DNA damage, thereby activating this pathway[1][3].