Bcl-2-associated X protein and Poly [ADP-ribose] polymerase 1 (BAX and PARP1)

Bcl-2-associated X protein (BAX) and Poly [ADP-ribose] polymerase 1 (PARP1) are two distinct but functionally linked proteins central to the regulation of cell death and DNA integrity. BAX (UniProt Q07812) is a pro-apoptotic member of the Bcl-2 family that, upon activation, translocates to the mitochondria to induce mitochondrial outer membrane permeabilization (MOMP), leading to the release of cytochrome c and subsequent caspase activation (PubMed: 10733517). PARP1 (UniProt P09874) is a nuclear enzyme primarily involved in the detection and repair of DNA single-strand breaks; however, during apoptosis, it is typically cleaved and inactivated by caspases to conserve cellular energy (PubMed: 7526156). In the context of cancer therapy, PARP1 is a major therapeutic target for PARP inhibitors (e.g., olaparib, rucaparib), which exploit synthetic lethality in tumors with homologous recombination deficiencies, such as BRCA mutations (PubMed: 22556261). While BAX is not yet a common direct clinical target, its expression and activation are frequently used as biomarkers for the efficacy of pro-apoptotic therapies, including those involving PARP inhibition. Together, these molecules serve as critical indicators of a cell's transition from DNA repair to programmed cell death.

Other names

Apoptosis regulator BAXBCL2L4Bcl-2-like protein 4Poly [ADP-ribose] polymerase 1ADPRTADPRT1PPOLPARP-1

PARP inhibitors act by competitively inhibiting the catalytic activity of PARP1 and by trapping the enzyme on damaged DNA, leading to double-strand breaks that are lethal in cells with homologous recombination deficiencies (synthetic lethality). BAX-mediated mechanisms involve the formation of oligomeric pores in the mitochondrial outer membrane (MOMP) to initiate the intrinsic apoptotic pathway, often occurring downstream of DNA damage or as a result of caspase-mediated PARP1 cleavage during the execution phase of cell death.