Department of Pharmacy, University of Naples "Federico II", Via D. Montesano 49, 80131 Napoli, Italy.
National Research Council, Institute of Crystallography, Sede Secondaria di Catania, Via Paolo Gaifami 18, 95126 Catania, Italy.
Biomolecules. 2022 May 24;12(6):741. doi: 10.3390/biom12060741.
Cationic porphyrins exhibit an amazing variety of binding modes and inhibition mechanisms of 20S proteasome. Depending on the spatial distribution of their electrostatic charges, they can occupy different sites on α rings of 20S proteasome by exploiting the structural code responsible for the interaction with regulatory proteins. Indeed, they can act as competitive or allosteric inhibitors by binding at the substrate gate or at the grooves between the α subunits, respectively. Moreover, the substitution of a charged moiety in the peripheral arm with a hydrophobic moiety revealed a "new" 20S functional state with higher substrate affinity and catalytic efficiency. In the present study, we expand our structure-activity relationship (SAR) analysis in order to further explore the potential of this versatile class of 20S modulators. Therefore, we have extended the study to additional macrocyclic compounds, displaying different structural features, comparing their interaction behavior on the 20S proteasome with previously investigated compounds. In particular, in order to evaluate how the introduction of a peptidic chain can affect the affinity and the interacting mechanism of porphyrins, we investigate the MTPyApi, a porphyrin derivatized with an Arg-Pro-rich antimicrobial peptide. Moreover, to unveil the role played by the porphyrin core, this was replaced with a corrole scaffold, a "contracted" version of the tetrapyrrolic ring due to the lack of a methine bridge. The analysis has been undertaken by means of integrated kinetic, Nuclear Magnetic Resonance, and computational studies. Finally, in order to assess a potential pharmacological significance of this type of investigation, a preliminary attempt has been performed to evaluate the biological effect of these molecules on MCF7 breast cancer cells in dark conditions, envisaging that porphyrins may indeed represent a powerful tool for the modulation of cellular proteostasis.
阳离子卟啉表现出 20S 蛋白酶体的惊人多种结合模式和抑制机制。根据其静电电荷的空间分布，它们可以通过利用负责与调节蛋白相互作用的结构密码，占据 20S 蛋白酶体α环上的不同位置。事实上，它们可以通过分别结合在底物门或α亚基之间的凹槽中，作为竞争性或别构抑制剂发挥作用。此外，在周围臂的带电部分用疏水性部分取代，揭示了具有更高底物亲和力和催化效率的“新”20S 功能状态。在本研究中，我们扩展了我们的结构-活性关系（SAR）分析，以进一步探索这种多功能 20S 调节剂的潜力。因此，我们已经将研究扩展到其他具有不同结构特征的大环化合物，比较它们在 20S 蛋白酶体上的相互作用行为与之前研究过的化合物。特别是，为了评估引入肽链如何影响卟啉的亲和力和相互作用机制，我们研究了 MTPyApi，一种衍生自富含精氨酸-脯氨酸的抗菌肽的卟啉。此外，为了揭示卟啉核心所起的作用，我们用一个 corrole 支架取代了它，corrole 是由于缺乏亚甲基桥而导致四吡咯环“收缩”的版本。通过综合动力学、核磁共振和计算研究进行了分析。最后，为了评估这种类型的研究的潜在药理学意义，我们初步尝试评估这些分子在 MCF7 乳腺癌细胞中的黑暗条件下的生物学效应，设想卟啉实际上可能成为调节细胞蛋白质平衡的有力工具。
