Abstract
The selective degradation of target proteins with small molecules is a novel approach to the treatment of various diseases, including cancer. We have developed a protein knockdown system with a series of hybrid small compounds that induce the selective degradation of target proteins via the ubiquitin–proteasome pathway. In this study, we designed and synthesized novel small molecules called SNIPER(TACC3)s, which target the spindle regulatory protein transforming acidic coiled-coil-3 (TACC3). SNIPER(TACC3)s induce poly-ubiquitylation and proteasomal degradation of TACC3 and reduce the TACC3 protein level in cells. Mechanistic analysis indicated that the ubiquitin ligase APC/CCDH1 mediates the SNIPER(TACC3)-induced degradation of TACC3. Intriguingly, SNIPER(TACC3) selectively induced cell death in cancer cells expressing a larger amount of TACC3 protein than normal cells. These results suggest that protein knockdown of TACC3 by SNIPER(TACC3) is a potential strategy for treating cancers overexpressing the TACC3 protein.
Highlights
The cell lysates were immunoprecipitated with anti-FLAG (TACC3) antibody, and the immunoprecipitates were eluted with an excess amount of either KHS108 or Me-BS to detect the APC/CCDH1 components that had associated with Transforming acidic coiled-coil-3 (TACC3) depending on SNIPER(TACC3) (Supplementary Figure S1)
This method enables the induction of a rapid degradation of a target even if it is a long-lived protein, which stands in contrast with the repression of protein synthesis by small interfering RNA (siRNA) and antisense oligonucleotides that require a longer time to achieve efficient knockdown
We have developed a series of SNIPER compounds targeting a variety of proteins, including CRABP-II and estrogen receptor α (ERα).[22,23,24,25,26,27,28]
Summary
Transforming acidic coiled-coil-3 (TACC3) is another spindle-regulatory protein.[4,5] During mitosis, TACC3 localizes to the mitotic spindle and has a critical role in spindle assembly, chromosomal function and mitotic progression.[6,7,8,9,10,11] Studies using microarray and immunohistochemical analysis showed that TACC3 is overexpressed in many human cancers, including ovarian cancer, breast cancer, squamous cell carcinoma and lymphoma.[12,13,14] Depletion of TACC3 results in chromosome alignment defects, multi-polar spindle formation, mitotic cell death and/or a postmitotic cell cycle arrest.[15,16,17,18,19,20] conditional disruption of TACC3 has been shown to regress thymic lymphomas in p53-deficient mice without inducing any overt abnormalities in normal tissues.[21]. SNIPER(TACC3)s decreased the cIAP1 level, the effect was less than Me-BS, suggesting that the SNIPER(TACC3)s simultaneously induces auto-ubiquitylation and proteasomal degradation of cIAP1, as observed with other SNIPERs.[22,28] Similar results were obtained in human breast adenocarcinoma MCF7 or human osteosarcoma U2OS cells when the cells were treated with 30 μM of SNIPER(TACC3)s for 6 h (Figure 1c). These results indicate that SNIPER(TACC3)s induce poly-ubiquitylation and proteasomal degradation of TACC3 proteins within cells.
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