Bcl-2 family controls mitochondrial outer membrane permeabilization by performing non-trivial pattern recognition

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Interactions between individual members of the B-cell lymphoma 2 (Bcl-2) family of proteins form a regulatory network governing mitochondrial outer membrane permeabilization (MOMP). Bcl-2 family initiated MOMP causes release of the inter-membrane pro-apoptotic proteins to cytosol and creates a cytosolic environment suitable for the executionary phase of apoptosis. Using mathematical modeling and computational simulation, we have analyzed the response of this regulatory network caused by the up-/downregulation of each individual member of the Bcl-2 family. As a result, a non-linear stimulus-response emerged, the characteristics of which are associated with bistability and switch-like behavior. Using the principal component analysis (PCA) we have shown that the Bcl-2 family classifies the random combinations of inputs into two distinct classes, and responds to these by one of the two qualitatively distinct outputs. As we showed, the emergence of this behavior requires specific organization of the interactions between particular Bcl-2 proteins.