Systems analysis of phosphorylation‐regulated Bcl‐2 interactions establishes a model to reconcile the controversy over the significance of Bcl‐2 phosphorylation

Article date: February 2019

By: Ting Song, Peiran Wang, Xiaoyan Yu, Anhui Wang, Gaobo Chai, Yudan Fan, Zhichao Zhang in Volume 176, Issue 3, pages 491-504

Background and Purpose

The biological significance of the multi‐site phosphorylation of Bcl‐2 at its loop region (T69, S70 and S87) has remained controversial for decades. This is a major obstacle for understanding apoptosis and anti‐tumour drug development.

Experimental Approach

We established a mathematical model into which a phosphorylation and de‐phosphorylation process of Bcl‐2 was integrated. Paclitaxel‐treated breast cancer cells were used as experimental models. Changes in the kinetics of binding with its critical partners, induced by phosphorylation of Bcl‐2 were experimentally obtained by surface plasmon resonance, using a phosphorylation‐mimicking mutant EEE‐Bcl‐2 (T69E, S70E and S87E).

Key Results

Mathematical simulations combined with experimental validation showed that phosphorylation regulates Bcl‐2 with different dynamics depending on the extent of Bcl‐2 phosphorylation and the phosphorylated Bcl‐2‐induced changes in binding kinetics. In response to Bcl‐2 homology 3 (BH3)‐only protein Bmf stress, Bcl‐2 phosphorylation switched from diminishing to enhancing the Bcl‐2 anti‐apoptotic ability with increased phosphorylation of Bcl‐2, and the turning point was 50% Bcl‐2 phosphorylation induced by 0.2 μM paclitaxel treatment. In contrast, Bcl‐2 phosphorylation enhanced the anti‐apoptotic ability of Bcl‐2 towards other BH3‐only proteins Bim, Bad and Puma, throughout the entire phosphorylation procedure.

Conclusions and Implications

The model could accurately predict the effects of anti‐tumour drugs that involve the Bcl‐2 family pathway, as shown with ABT‐199 or etoposide.

DOI: 10.1111/bph.14555

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