Institute of Pharmacology and Toxicology, Jena University Hospital, 07747 Jena, Germany.
Department of Pharmacology and Toxicology, University of Toronto, Toronto M5S 1A8, ON, Canada.
Cell Rep. 2019 Feb 5;26(6):1473-1488.e9. doi: 10.1016/j.celrep.2019.01.049.
Phosphorylation of heptahelical receptors is thought to regulate G protein signaling, receptor endocytosis, and non-canonical signaling via recruitment of β-arrestins. We investigated chemokine receptor functionality under phosphorylation-deficient and β-arrestin-deficient conditions by studying interneuron migration in the embryonic cortex. This process depends on CXCL12, CXCR4, G protein signaling and on the atypical CXCL12 receptor ACKR3. We found that phosphorylation was crucial, whereas β-arrestins were dispensable for ACKR3-mediated control of CXCL12 levels in vivo. Cortices of mice expressing phosphorylation-deficient ACKR3 exhibited a major interneuron migration defect, which was accompanied by excessive activation and loss of CXCR4. Cxcl12-overexpressing mice mimicked this phenotype. Excess CXCL12 caused lysosomal CXCR4 degradation, loss of CXCR4 responsiveness, and, ultimately, similar motility defects as Cxcl12 deficiency. By contrast, β-arrestin deficiency caused only a subtle migration defect mimicked by CXCR4 gain of function. These findings demonstrate that phosphorylation regulates atypical chemokine receptor function without β-arrestin involvement in chemokine sequestration and non-canonical signaling.
七次跨膜受体的磷酸化被认为可以调节 G 蛋白信号转导、受体内吞和通过招募β-arrestin 的非典型信号转导。我们通过研究胚胎皮层中的中间神经元迁移来研究趋化因子受体在磷酸化缺陷和β-arrestin 缺陷条件下的功能。这个过程依赖于 CXCL12、CXCR4、G 蛋白信号和非典型趋化因子受体 ACKR3。我们发现，磷酸化对于 ACKR3 介导的体内 CXCL12 水平的控制至关重要，而β-arrestin 则是可有可无的。表达磷酸化缺陷 ACKR3 的小鼠皮层表现出主要的中间神经元迁移缺陷，伴随着 CXCR4 的过度激活和丧失。Cxcl12 过表达的小鼠模拟了这种表型。过量的 CXCL12 导致溶酶体 CXCR4 降解、CXCR4 反应性丧失，最终导致与 Cxcl12 缺乏相似的运动缺陷。相比之下，β-arrestin 缺陷仅导致 CXCR4 功能获得的微小迁移缺陷。这些发现表明，磷酸化调节非典型趋化因子受体的功能，而不涉及β-arrestin 参与趋化因子隔离和非典型信号转导。
