Biology subjects

McEwan, B.

Publications and source records attributed to McEwan, B..

2 recordsLinked to original sources

bioRxiv2024

Substrate recognition principles for PP2A-B55

The PP2A-B55 phosphatase regulates a plethora of signaling pathways throughout eukaryotes. How PP2A-B55 selects its substrates presents a severe knowledge gap. By integrating AlphaFold modelling with comprehensive high resolution mutational scanning, we show that -helices in substrates bind B55 through an evolutionary conserved mechanism. Despite a large diversity in sequence and composition, these -helices share key amino acid determinants that engage discrete hydrophobic and electrostatic patches. Using deep learning protein design, we generate a specific and potent competitive peptide inhibitor of PP2A-B55 substrate interactions. With this inhibitor, we uncover that PP2A-B55 regulates the nuclear exosome targeting complex by binding to an -helical recruitment module in RBM7. Collectively, our findings provide a framework for the understanding and interrogation of PP2A-B55 in health and disease. One sentence summary-helices in PP2A-B55 substrates bind a conserved pocket on B55 through a common mechanism that is conserved in eukaryotes.

cell biology↗

bioRxiv2021

Cellular toxicity of iHAP1 and DT-061 does not occur through PP2A-B56 targeting

PP2A is an abundant phosphoprotein phosphatase that acts as a tumor suppressor. For this reason, compounds able to activate PP2A are attractive anticancer agents. The small molecule compounds iHAP1 and DT-061 have recently been reported by Leonard et al. (2020) and Morita et al. (2020) in Cell to selectively stabilize specific PP2A-B56 complexes which mediate cell killing. Here, we show that this is not the case and question key findings in these papers. Through genome wide CRISPR-Cas9 screens, we uncover the biological pathways targeted by these compounds. We find that iHAP1 directly blocks microtubule assembly both in vitro and in vivo and thus acts as a microtubule poison. In contrast, DT-061 disrupts both the Golgi apparatus and the endoplasmic reticulum and we directly visualize DT-061 in cytoplasmic granules that co-localize with Golgi markers. Our work demonstrates that iHAP1 and DT-061 cannot be used for dissecting PP2A-B56 biology.

cell biology↗