Aurora kinase A-mediated phosphorylation triggers structural alteration of Rab1A to enhance ER complexity during mitosis.

Morphological rearrangement of the endoplasmic reticulum (ER) is critical for metazoan mitosis. Yet, how the ER is remodeled by the mitotic signaling remains unclear. Here, we report that mitotic Aurora kinase A (AURKA) employs a small GTPase, Rab1A, to direct ER remodeling. During mitosis, AURKA phosphorylates Rab1A at Thr75. Structural analysis demonstrates that Thr75 phosphorylation renders Rab1A in a constantly active state by preventing interaction with GDP-dissociation inhibitor (GDI). Activated Rab1A is retained on the ER and induces the oligomerization of ER-shaping protein RTNs and REEPs, eventually triggering an increase of ER complexity. In various models, from Caenorhabditis elegans and Drosophila to mammals, inhibition of Rab1AThr75 phosphorylation by genetic modifications disrupts ER remodeling. Thus, our study reveals an evolutionarily conserved mechanism explaining how mitotic kinase controls ER remodeling and uncovers a critical function of Rab GTPases in metaphase.

A Temporal PROTAC Cocktail-Mediated Sequential Degradation of AURKA Abrogates Acute Myeloid Leukemia Stem Cells.

AURKA is a potential kinase target in various malignancies. The kinase-independent oncogenic functions partially disclose the inadequate efficacy of the kinase inhibitor in a Phase III clinical trial. Simultaneously targeting the catalytic and noncatalytic functions of AURKA may be a feasible approach. Here, a set of AURKA proteolysis targeting chimeras (PROTACs) are developed. The CRBN-based dAurA383 preferentially degrades the highly abundant mitotic AURKA, while cIAP-based dAurA450 degrades the lowly abundant interphase AURKA in acute myeloid leukemia (AML) cells. The proteomic and transcriptomic analyses indicate that dAurA383 triggers the "mitotic cell cycle" and "stem cell" processes, while dAurA450 inhibits the "MYC/E2F targets" and "stem cell" processes. dAurA383 and dAurA450 are combined as a PROTAC cocktail. The cocktail effectively degrades AURKA, relieves the hook effect, and synergistically inhibits AML stem cells. Furthermore, the PROTAC cocktail induces AML regression in a xenograft mouse model and primary patient blasts. These findings establish the PROTAC cocktail as a promising spatial-temporal drug administration strategy to sequentially eliminate the multifaceted functions of oncoproteins, relieve the hook effect, and prevent cancer stem cell-mediated drug resistance.

Modulation of oxidative phosphorylation augments antineoplastic activity of mitotic aurora kinase inhibition.

Uncontrolled mitosis is one of the most important features of cancer, and mitotic kinases are thought to be ideal targets for anticancer therapeutics. However, despite numerous clinical attempts spanning decades, clinical trials for mitotic kinase-targeting agents have generally stalled in the late stages due to limited therapeutic effectiveness. Alisertib (MLN8237) is a promising oral mitotic aurora kinase A (AURKA, Aurora-A) selective inhibitor, which is currently under several clinical evaluations but has failed in its first Phase III trial due to inadequate efficacy. In this study, we performed genome-wide CRISPR/Cas9-based screening to identify vulnerable biological processes associated with alisertib in breast cancer MDA-MB-231 cells. The result indicated that alisertib treated cancer cells are more sensitive to the genetic perturbation of oxidative phosphorylation (OXPHOS). Mechanistic investigation indicated that alisertib treatment, as well as other mitotic kinase inhibitors, rapidly reduces the intracellular ATP level to generate a status that is highly addictive to OXPHOS. Furthermore, the combinational inhibition of mitotic kinase and OXPHOS by alisertib, and metformin respectively, generates severe energy exhaustion in mitotic cells that consequently triggers cell death. The combination regimen also enhanced tumor regression significantly in vivo. This suggests that targeting OXPHOS by metformin is a potential strategy for promoting the therapeutic effects of mitotic kinase inhibitors through the joint targeting of mitosis and cellular energy homeostasis.

Structure-based drug design: Synthesis and biological evaluation of quinazolin-4-amine derivatives as selective Aurora A kinase inhibitors.

Aurora kinases play critical roles in the regulation of the cell cycle and mitotic spindle assembly. Aurora A kinase, a member of the Aurora protein family, is frequently highly expressed in tumors, and selective Aurora A inhibition serves as a significant component of anticancer therapy. However, designing highly selective Aurora A inhibitors is difficult because Aurora A and B share high homology and differ only by three residues in their ATP-binding pockets. Through structure-based drug design, we designed and synthesized a series of novel quinazolin-4-amine derivatives. These derivatives act as selective Aurora A kinase inhibitors by exploiting the structural differences between Aurora A and B. The selectivities of most compounds were improved (the best up to >757-fold) when comparing with the lead compound (3-fold). In vitro biochemical and cellular assays revealed that compound 6 potently inhibited Aurora A kinase and most human tumor cells. Furthermore, compound 6 effectively suppressed carcinoma, such as triple-negative breast cancers (TNBC) in an animal model. Therefore, compound 6 might serve as a promising anticancer drug. Moreover, through molecular dynamic (MD) analysis, we have identified that a salt bridge formed in Aurora B is key contributor for the isoform selectivity of the inhibitor. This salt bridge has not been previously detected in the reported crystal structure of Aurora B. These results might provide a crucial basis for the further development of highly potent inhibitors with high selectivity for Aurora A.