B-cell lymphoma 2 family apoptosis regulatory proteins (Bcl-2 family)

The B-cell lymphoma 2 (Bcl-2) family of proteins consists of critical regulators of the intrinsic (mitochondrial) pathway of apoptosis (Source: UniProt P10415). This family is divided into three groups based on their function and Bcl-2 homology (BH) domains: anti-apoptotic members (e.g., Bcl-2, Bcl-xL, Mcl-1), pro-apoptotic pore-formers (e.g., Bax, Bak), and pro-apoptotic BH3-only initiators (e.g., Bim, Bid, Bad, Puma). The balance between these opposing groups determines cell fate; an overabundance of anti-apoptotic proteins often allows cancer cells to evade programmed cell death and develop resistance to chemotherapy (Source: PubMed PMC4445518). Therapeutic strategies primarily focus on "BH3 mimetics," small molecules that inhibit anti-apoptotic members to restore the apoptotic threshold. Venetoclax, a selective Bcl-2 inhibitor, has demonstrated significant clinical success in treating chronic lymphocytic leukemia and acute myeloid leukemia (Source: FDA Venclexta Label). However, challenges such as resistance mediated by Mcl-1 upregulation and toxicities like thrombocytopenia or tumor lysis syndrome remain key considerations in drug development (Source: Blood, 2019, PMID: 31040141).

Other names

Bcl-2 familyB-cell CLL/lymphoma 2 familyApoptosis regulator Bcl-2 familyBcl-2 family proteins

BH3 mimetics bind to the hydrophobic groove of anti-apoptotic Bcl-2 family members (such as Bcl-2, Bcl-xL, or Mcl-1), displacing pro-apoptotic BH3-only proteins. This release allows the activation of pore-forming proteins Bax and Bak, leading to mitochondrial outer membrane permeabilization (MOMP), cytochrome c release, and subsequent caspase activation and cell death (Source: Nature Reviews Drug Discovery, 2017, PMID: 28360414; PubMed PMC4445518).