부산대학교 도서관

Protein phosphatase 2A (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 compounds iHAP1 and DT‐061 have recently been reported to selectively stabilize specific PP2A‐B56 complexes to mediate cell killing. We were unable to detect direct effects of iHAP1 and DT‐061 on PP2A‐B56 activity in biochemical assays and composition of holoenzymes. Therefore, we undertook genome‐wide CRISPR‐Cas9 synthetic lethality screens to uncover biological pathways affected by these compounds. We found that knockout of mitotic regulators is synthetic lethal with iHAP1 while knockout of endoplasmic reticulum (ER) and Golgi components is synthetic lethal with DT‐061. Indeed we showed 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 ER and lipid synthesis associated with these structures. Our work provides insight into the biological pathways perturbed by iHAP1 and DT‐061 causing cellular toxicity and argues that these compounds cannot be used for dissecting PP2A‐B56 biology. Synopsis: DT‐061 and iHAP1 are small‐molecule compounds described to be activators of protein phosphatase 2A (PP2A). This work shows that their cellular toxicity is not mediated by direct effects on PP2A, but instead involves disruption of Golgi/ER structures and microtubule depolymerization, respectively. Chemogenetic profiling of DT‐061 and iHAP1 uncovers potential cellular pathways affected by the compounds.iHAP1 acts as a microtubule poison arresting cells in prometaphase.DT‐061 disrupts Golgi and ER structures and lipid synthesis associated with these structures.No direct effects of DT‐061 and iHAP1 on PP2A complexes could be established. [ABSTRACT FROM AUTHOR]