Abstract
The BCL-2 protein family governs critical cell-fate decisions between survival, senescence, and apoptosis, yet the dynamical principles underlying these choices remain poorly understood. Here, we integrate mathematical modeling, bifurcation analysis, and stochastic simulations to dissect how BCL-2 network architecture encodes multistability and fate plasticity. Our coarse-grained model reveals tristable regimes requiring cooperative BH3-only and anti-apoptotic BCL-2 interactions, with stochastic fluctuations driving heterogeneous fate commitments in genetically identical cells. Comparative analysis of mechanistic models demonstrates that while bistability emerges from canonical BCL-2 interactions, robust tristability requires additional regulatory constraint, explaining the metastability of senescence in stress responses. Hybrid models further show that BH3-only binding cooperativity enables multistability, but physiological senescence likely depends on additional control mechanisms. These results establish a unified framework linking molecular interactions to cell-fate dynamics, with implications for targeting apoptosis resistance in disease.