Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.22.215814v1?rss=1 Authors: Wang, R. K., Abdelbaki, A. M., Ascanelli, C., Fung, A. Y., Rasmusson, T., Roberts, K., Lindon, C. Abstract: Targeted protein degradation tools are becoming a new therapeutic modality, allowing small molecule ligands to be reformulated as heterobifunctional molecules (referred to as PROTACs, for PROteolysis Targeting Chimeras) that recruit a ubiquitin ligase to the target of interest, leading to ubiquitination of the target and its destruction via the ubiquitin-proteasome system. A number of PROTACs against targets of clinical interest have been described, but detailed descriptions of the cell biology modulated by PROTACs are missing from the literature. Here we describe the functional characterization of a PROTAC derived from AURKA inhibitor MLN8237 (alisertib). We demonstrate efficient and specific destruction of both endogenous and overexpressed AURKA by Cereblon-directed PROTACs. At the subcellular level, we find differential targeting of AURKA on the mitotic spindle compared to centrosomes. The phenotypic consequences of PROTAC treatment are therefore distinct from those mediated by alisertib, and in mitotic cells differentially regulate the centrosome- and chromatin-based microtubule spindle assembly pathways. In interphase cells we find that PROTAC-mediated clearance of non-centrosomal AURKA, and not PROTAC-mediated inhibition of its activity, efficiently modulates the cytoplasmic role played by AURKA in mitochondrial dynamics, whilst the centrosomal pool is refractory to PROTAC-mediated clearance. Our results point to differential accessibility of subcellular pools of substrate, governed by substrate conformation or localization in compartments more or less accessible to PROTAC action, a phenomenon not previously described for this new class of drugs. Copy rights belong to original authors. Visit the link for more info