PP2A is an abundant ser/thr protein phosphatase that act as a tumor suppressor by antagonizing multiple oncogenic kinases. For this reason, compounds able to activate PP2A holoenzymes are attractive anticancer agents. DT-061 and iHAP are phenothiazine derivatives that have recently been claimed to activate specific PP2A-B56 complexes to mediate cell killing. Here we show that iHAP and DT-061 do not activate PP2A-B56 complexes in vitro and that CRISPR removal of B56 regulatory subunits does not affect cellular toxicity of the compounds. Through genome-wide CRISPR screens we uncover the cell killing mechanism of iHAP and DT-061. We find that iHAP is a microtubule poison and removal of mitotic regulators causes hypersensitivity. In contrast, DT-061 disrupts both Golgi and ER consistent with an impact on cellular lipid composition. Indeed, we directly visualize DT-061 in cytoplasmic granules that co-localize with Golgi markers shortly after addition of the compound. Our work uncovers that well known side-effects of phenothiazine derived compounds cause cell killing by iHAP and DT-061 arguing that these compounds cannot be used for dissecting PP2A biology.
[doi:10.25345/C5S53H]
[dataset license: CC0 1.0 Universal (CC0 1.0)]
Keywords: PP2A ; phosphatase ; tumor ; kinase ; holoenzyme ; DT-061 ; iHAP ; PP2A-B56 ; B56 ; cell killing ; golgi ; phenothiazine
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Arminja Kettenbach, The Geisel School of Medicine at Dartmouth, United States |
Submitting User: | madamo |
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