br Results br Discussion The A nidulans Aurora
Discussion The A. nidulans Aurora kinase displays diverse locations during mitosis and we show here that it also locates to hyphal regions where septa subsequently form, to the septal pore region of newly formed septa and displays a hexamethonium synthesis specific location to mature septa. To investigate its potential functions we generated the temperature sensitive aurA3 allele. Inactivation of Aurora had devastating effects on mitosis, resulted in loss of SAC function and also had a marked effect on cell growth and viability.
Conclusions Aurora kinases display dynamic cell cycle specific distributions related to, and predictive of, the roles these kinases play during cell growth and division. We demonstrate that A. nidulans Aurora displays dynamic and diverse locations to the mitotic apparatus and unexpected interphase locations. By generating a temperature sensitive allele to inactivate Aurora kinase activity we confirmed roles for Aurora in the formation and function of the mitotic spindle and in SAC activation. Our studies also reveal an accumulation of Aurora occurs during a mitotic SAC arrest making it a candidate for the unknown regulator whose mitotic protein synthesis is involved in inactivating the SAC in A. nidulans. Following mitosis Aurora locates to cytoplasmic sites predictive of where septa form, at forming septa and new septal pores. Such dynamic locations are perhaps predictive of roles in selecting sites of septation, in septal formation and septal pore generation. In addition, Aurora also locates to existing mature septa specifically after mitosis suggesting it might be involved in post mitotic septal pore opening. Finally, Aurora function is required for viability during spore germination. However, further experimentation will be required to address these intriguing potential Aurora functions specific to filamentous fungi and distinct from its mitotic spindle functions.
Acknowledgments We thank all past and present members of the Osmani Lab for many helpful discussions. This work was supported by the National Institutes of Health (P01 GM068087-08S1) to SAO.
Introduction Aurora kinases are a family of highly conserved serine/threonine protein kinases found to be involved in multiple mitotic events. There are three homologs of Aurora kinases in humans. Aurora A (A2k) and Aurora B kinase (A1k) are ubiquitously present in various cells, whereas Aurora C kinase (A3k) is highly expressed only in testis. Aurora A and Aurora B kinase are attractive targets for cancer therapy. Some Aurora kinase inhibitors have proven effective on a wide range of tumor types in clinical trials. Danusertib (PHA-739358) is a pan-Aurora kinase inhibitor found by Nerviano Medical Science (structure is a 3-aminopyrazole derivative). It has been developed for Chronic Myeloid Leukemia treatment. Alisertib (MLN-8237) is a selective Aurora A kinase inhibitor found by Takeda pharmaceuticals. It has been developed for small cell lung cancer (SCLC) treatment. SAR156497 has been studied in clinical trial by Sanofi. These clinical data are very encouraging and promising for development of structurally different Aurora kinase inhibitors. Previously we reported the design and the synthesis of a new class of orally active Aurora A kinase inhibitor 1 (Fig. 1) by transforming the core structure of VX-680,9, 10 which strongly and selectively inhibited Aurora A, B and C kinases but offered poor oral absorption. The Ki value of compound 1 against Aurora A kinase was under 0.001μM. Compound 1 was more potent against Aurora A kinase than VX-680 whose Ki value was 0.002μM as measured by our assay system. One of the problems with compound 1 was that it inhibited 2C19 of CYP (Cytochrome P450) strongly (IC50<0.4μM). In this report, to overcome this problem, we attempted the optimization of 2-substituent of the 3-cyanopyridine ring of compound 1.
Results and discussion