Regulator of G protein signaling (RGS) proteins are negative modulators of G protein signaling that have emerged as promising drug targets to improve specificity and reduce side effects of G protein–coupled receptor–related therapies. Several small molecule RGS protein inhibitors have been identified; however, enhancing RGS protein function is often more clinically desirable but presents a challenge. Low protein levels of RGS2 are associated with various pathologies, including hypertension and heart failure. For this reason, RGS2 is a prominent example wherein enhancing its function would be beneficial. RGS2 is rapidly ubiquitinated and proteasomally degraded, providing a point of intervention for small molecule RGS2-stabilizing compounds. We previously identified a novel cullin-RING E3 ligase utilizing F-box only protein 44 (FBXO44) as the substrate recognition component. Here, we demonstrate that RGS2 associates with FBXO44 through a stretch of residues in its N terminus. RGS2 contains four methionine residues close to the N terminus that can act as alternative translation initiation sites. The shorter translation initiation variants display reduced ubiquitination and proteasomal degradation as a result of lost association with FBXO44. In addition, we show that phosphorylation of Ser³ may be an additional mechanism to protect RGS2 from FBXO44-mediated proteasomal degradation. These findings contribute to elucidating mechanisms regulating steady state levels of RGS2 protein and will inform future studies to develop small molecule RGS2 stabilizers. These would serve as novel leads in pathologies associated with low RGS2 protein levels, such as hypertension, heart failure, and anxiety.

中文翻译：

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N端靶向G蛋白信号蛋白2的调节剂，仅用于F-Box蛋白44介导的蛋白酶体降解

G蛋白信号转导（RGS）蛋白的调节剂是G蛋白信号转导的负调节剂，已成为有望改善G蛋白偶联受体相关疗法的特异性并减少其副作用的药物靶标。已经鉴定出几种小分子RGS蛋白抑制剂；它们的合成方法包括：然而，增强RGS蛋白功能通常在临床上更合乎需要，但却带来了挑战。RGS2的低蛋白水平与多种病理相关，包括高血压和心力衰竭。因此，RGS2是一个突出的例子，其中增强其功能将是有益的。RGS2迅速泛素化并被蛋白酶降解，为稳定小分子RGS2化合物提供了干预点。我们先前确定了一种新型的cullin-RING E3连接酶，利用仅F-box蛋白44（FBXO44）作为底物识别组件。在这里，我们证明RGS2通过其N末端的一连串残基与FBXO44缔合。RGS2包含靠近N末端的四个蛋氨酸残基，可以充当替代的翻译起始位点。较短的翻译起始变体由于与FBXO44失去关联而显示出减少的泛素化和蛋白酶体降解。此外，我们表明丝氨酸的磷酸化 较短的翻译起始变体由于与FBXO44失去关联而显示出减少的泛素化和蛋白酶体降解。此外，我们表明丝氨酸的磷酸化 较短的翻译起始变体由于与FBXO44失去关联而显示出减少的泛素化和蛋白酶体降解。此外，我们表明丝氨酸的磷酸化^图3可能是保护RGS2免受FBXO44介导的蛋白酶体降解的另一种机制。这些发现有助于阐明调节RGS2蛋白质稳态水平的机制，并将为将来的研究开发小分子RGS2稳定剂提供参考。这些将作为与低RGS2蛋白水平相关的病理学的新线索，例如高血压，心力衰竭和焦虑。