The E3 ligase adaptor SPOP, overexpressed in the nucleus but frequently dislocated into the cytoplasm in all clear cell Renal Cell Carcinomas (ccRCC), serves as a regulatory hub to promote kidney cancer through the ubiquitination and degradation of multiple downstream cancer proteins. Recently, our identification of a selective small‐molecule inhibitor of the SPOP‐phosphatase and tensin homolog (PTEN) interaction has demonstrated that the oncogenic SPOP‐protein interaction would be a druggable target specific to ccRCC therapy. To our knowledge, this is the first time such a small‐molecule inhibitor has been developed. Herein, we have identified a peptide binder for the SPOP‐MATH domain that disrupts the oncogenic SPOP‐protein interactions in kidney cancer cells. Computational design and biophysical characterization yielded peptide Pep38 that binds to the MATH domain of SPOP and competes on PTEN‐binding to SPOP in vitro. The X‐ray complex structure reveals that the peptide binder features the following combination: one, a mimic of the native peptide binder and two, an additional β‐strand motif in sequence, which could contribute to increased binding affinity. In order to improve cellular permeability, we fused Pep38 with the delivery peptide TAT to prepare peptide TAT38, which inhibits the endogenous substrate binding to SPOP and suppresses the proliferation of the ccRCC cells. Our identification of the peptide inhibitors for SPOP‐protein interactions provides further validation that the oncogenic SPOP‐signaling pathway in ccRCC could be a druggable target specifically applicable to the therapy of kidney cancers.

中文翻译：

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E3连接酶衔接子SPOP的肽结合剂破坏肾脏癌细胞中的致癌SPOP-蛋白质相互作用。

E3连接酶衔接子SPOP在细胞核中过表达，但在所有透明细胞肾细胞癌（ccRCC）中经常脱位到细胞质中，可作为调节枢纽，通过多种下游癌症蛋白的泛素化和降解来促进肾癌。最近，我们对SPOP磷酸酶和张力蛋白同源物（PTEN）相互作用的选择性小分子抑制剂的鉴定表明，致癌性SPOP蛋白相互作用是ccRCC治疗的药物目标。据我们所知，这是第一次开发出这种小分子抑制剂。在本文中，我们已经确定了SPOP-MATH域的肽结合剂，该结合剂可破坏肾癌细胞中的致癌SPOP-蛋白相互作用。体外。X射线复合物结构揭示了该肽结合剂具有以下组合：一种是天然肽结合剂的模拟物，其二是序列中的另一个β链基序，这可能有助于增加结合亲和力。为了提高细胞通透性，我们将Pep38与递送肽TAT融合在一起以制备肽TAT38，该肽抑制内源性底物与SPOP的结合并抑制ccRCC细胞的增殖。我们对SPOP蛋白相互作用的肽抑制剂的鉴定进一步证实了ccRCC中的致癌SPOP信号通路可能是可用于治疗肾癌的药物靶标。