Otago Pharmacometrics Group, School of Pharmacy, University of Otago, Dunedin, New Zealand.
Department of Pharmacology and Toxicology, University of Otago, Dunedin, New Zealand.
Br J Pharmacol. 2020 Aug;177(15):3449-3463. doi: 10.1111/bph.15066. Epub 2020 May 15.
Biased agonism describes the ability of ligands to differentially regulate multiple signalling pathways when coupled to a single receptor. Signalling is affected by rapid agonist-induced receptor internalisation. Hence, the conventional use of equilibrium models may not be optimal, because (i) receptor numbers vary with time and, in addition, (ii) some pathways may show non-monotonic profiles over time.
Data were available from internalisation, cAMP inhibition and phosphorylation of ERK (pERK) of the cannabinoid-1 (CB ) receptor using a concentration series of six CB ligands (CP55,940, WIN55,212-2, anandamide, 2-arachidonylglycerol, Δ -tetrahydrocannabinol and BAY59,3074). The joint kinetic model of CB signalling was developed to simultaneously describe the time-dependent activities in three signalling pathways. Based on the insights from the kinetic model, fingerprint profiles of CB ligand bias were constructed and visualised.
A joint kinetic model was able to capture the signalling profiles across all pathways for the CB receptor simultaneously for a system that was not at equilibrium. WIN55,212-2 had a similar pattern as 2-arachidonylglycerol (reference). The other agonists displayed bias towards internalisation compared to cAMP inhibition. However, only Δ -tetrahydrocannabinol and BAY59,3074 demonstrated bias in the pERK-cAMP pathway comparison. Furthermore, all the agonists exhibited little preference between internalisation and pERK.
This is the first joint kinetic assessment of biased agonism at a GPCR (e.g. CB receptor) under non-equilibrium conditions. Kinetic modelling is a natural method to handle time-varying data when traditional equilibria are not present and enables quantification of ligand bias.
偏性激动描述了配体与单个受体结合时，对多个信号通路进行差异化调控的能力。信号转导受到快速激动剂诱导的受体内化的影响。因此，传统的平衡模型的使用可能并不理想，因为 (i) 受体数量随时间而变化，而且 (ii) 某些通路在时间上可能呈现非单调的分布。
使用 6 种 CB 配体（CP55,940、WIN55,212-2、anandamide、2-花生四烯酰甘油、Δ-四氢大麻酚和 BAY59,3074）的浓度系列，提供了关于大麻素-1 (CB) 受体的内化、cAMP 抑制和 ERK 磷酸化 (pERK) 的数据。建立了 CB 信号的联合动力学模型，以同时描述三个信号通路中随时间变化的活性。基于动力学模型的见解，构建并可视化了 CB 配体偏性的指纹图谱。
对于一个非平衡系统，联合动力学模型能够同时捕获所有信号通路的信号分布。WIN55,212-2 与 2-花生四烯酰甘油（参照）具有相似的模式。与 cAMP 抑制相比，其他激动剂显示出向内化的偏向性。然而，只有 Δ-四氢大麻酚和 BAY59,3074 在 pERK-cAMP 通路比较中显示出偏性。此外，所有激动剂在内化和 pERK 之间表现出很少的偏好。
这是在非平衡条件下对 GPCR（如 CB 受体）进行偏性激动的首次联合动力学评估。动力学建模是处理不存在传统平衡时随时间变化的数据的自然方法，并且能够量化配体偏性。
