Differential and competitive regulation of human melanocortin 1 receptor signaling by β-arrestin isoforms
Differential and competitive regulation of human melanocortin 1 receptor signaling by β-arrestin isoforms
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DOI：
10.1242/jcs.128322
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发表时间：
2013-08-15
影响因子：
4
通讯作者：
Garcia-Borron, Jose C.
中科院分区：
文献类型：
--
作者：
Abrisqueta, Marta;Herraiz, Cecilia;Garcia-Borron, Jose C.
黑素皮质素1受体（MC 1 R）是一种G蛋白偶联受体（GPCR），对黑素细胞增殖和分化的调节至关重要。MC 1 R被黑皮质素激素激活触发cAMP途径，并刺激细胞外信号调节蛋白激酶ERK 1和ERK 2，以促进光保护性真黑素色素的合成，以及其他作用。来自大多数GPCR的信号由胞质多功能衔接蛋白的β-抑制蛋白（ARRB）家族调节，其介导GPCR-激动剂复合物的信号终止和内吞作用。广泛表达的非视觉β-arrestin 1（ARRB 1）和β-arrestin 2（ARRB 2）高度相似，但功能不同。它们在MC 1 R调节中的作用尚不清楚。使用免疫共沉淀，凝胶过滤色谱，共聚焦显微镜，siRNA介导的敲低和功能测定的组合，我们证明了激动剂独立的竞争相互作用的ARRB 1和ARRB 2与MC 1 R，这也可能是独立的丝氨酸/苏氨酸残基的磷酸化的C-末端的MC 1 R。ARRB的作用是亚型特异性的; ARRB 2抑制MC 1 R激动剂依赖性cAMP的产生，但不抑制ERK活化，刺激内化，并与内吞囊泡中的受体表现出延长的共定位。相比之下，ARRB 1对内化或功能偶联没有影响，但与ARRB 2竞争结合MC 1 R，这可能通过置换抑制性ARRB 2来增加信号传导。这些数据表明，一种新的机制MC 1 R的功能调节的基础上的相对表达ARRB亚型，与可能的活化ARRB 1依赖性的影响所产生的抑制ARRB 2-MC 1 R的相互作用的部分救济。因此，功能中性的ARRB亚型竞争性取代抑制性ARRB可能会产生范式转换信号促进效应，以微调某些GPCR下游的信号传导。
The melanocortin 1 receptor (MC1R) is a G-protein-coupled receptor (GPCR) crucial for the regulation of melanocyte proliferation and differentiation. MC1R activation by melanocortin hormones triggers the cAMP pathway and stimulates the extracellular-signal-regulated protein kinases ERK1 and ERK2 to promote synthesis of photoprotective eumelanin pigments, among other effects. Signaling from most GPCRs is regulated by the beta-arrestin (ARRB) family of cytosolic multifunctional adaptor proteins, which mediate signal termination and endocytosis of GPCR-agonist complexes. The ubiquitously expressed non-visual beta-arrestin1 (ARRB1) and beta-arrestin2 (ARRB2) are highly similar but not functionally equivalent. Their role in the regulation of MC1R is unknown. Using a combination of co-immunoprecipitation, gel filtration chromatography, confocal microscopy, siRNA-mediated knockdown and functional assays, we demonstrated agonist-independent competitive interactions of ARRB1 and ARRB2 with MC1R, which might also be independent of phosphorylation of Ser/Thr residues in the C-terminus of the MC1R. The effects of ARRBs were isoform specific; ARRB2 inhibited MC1R agonist-dependent cAMP production but not ERK activation, stimulated internalization and showed prolonged co-localization with the receptor in endocytic vesicles. By contrast, ARRB1 had no effect on internalization or functional coupling, but competed with ARRB2 for binding MC1R, which might increase signaling by displacement of inhibitory ARRB2. These data suggest a new mechanism of MC1R functional regulation based on the relative expression of ARRB isoforms, with possible activatory ARRB1-dependent effects arising from partial relief of inhibitory ARRB2-MC1R interactions. Thus, competitive displacement of inhibitory ARRBs by functionally neutral ARRB isoforms might exert a paradigm-shifting signal-promoting effect to fine-tune signaling downstream of certain GPCRs.