Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada.
Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON L8S 4L8, Canada.
Cells. 2019 Nov 19;8(11):1462. doi: 10.3390/cells8111462.
The universal second messenger cAMP regulates diverse intracellular processes by interacting with ubiquitously expressed proteins, such as Protein Kinase A (PKA) and the Exchange Protein directly Activated by cAMP (EPAC). EPAC is implicated in multiple pathologies, thus several EPAC-specific inhibitors have been identified in recent years. However, the mechanisms and molecular interactions underlying the EPAC inhibition elicited by such compounds are still poorly understood. Additionally, being hydrophobic low molecular weight species, EPAC-specific inhibitors are prone to forming colloidal aggregates, which result in non-specific aggregation-based inhibition (ABI) in aqueous systems. Here, we review from a biophysical perspective the molecular basis of the specific and non-specific interactions of two EPAC antagonists-CE3F4R, a non-competitive inhibitor, and ESI-09, a competitive inhibitor of EPAC. Additionally, we discuss the value of common ABI attenuators (e.g., TX and HSA) to reduce false positives at the expense of introducing false negatives when screening aggregation-prone compounds. We hope this review provides the EPAC community effective criteria to evaluate similar compounds, aiding in the optimization of existing drug leads, and informing the development of the next generation of EPAC-specific inhibitors.
普遍的第二信使 cAMP 通过与广泛表达的蛋白质（如蛋白激酶 A（PKA）和 cAMP 直接激活的交换蛋白（EPAC））相互作用，调节多种细胞内过程。EPAC 与多种病理学有关，因此近年来已经鉴定出几种 EPAC 特异性抑制剂。然而，这些化合物引起的 EPAC 抑制的机制和分子相互作用仍知之甚少。此外，由于 EPAC 特异性抑制剂是疏水性的低分子量物质，因此容易形成胶体聚集物，从而导致在水性系统中基于非特异性聚集的抑制（ABI）。在这里，我们从生物物理的角度综述了两种 EPAC 拮抗剂-CE3F4R（非竞争性抑制剂）和 ESI-09（EPAC 的竞争性抑制剂）的特异性和非特异性相互作用的分子基础。此外，我们还讨论了常见的 ABI 衰减剂（例如 TX 和 HSA）的价值，这些衰减剂可以降低假阳性率，但在筛选易聚集化合物时会引入假阴性。我们希望本综述为 EPAC 社区提供了评估类似化合物的有效标准，有助于优化现有药物先导物，并为下一代 EPAC 特异性抑制剂的开发提供信息。
