Immunosuppressive and anti-angiogenic sphingosine 1-phosphate receptor-1 agonists induce ubipuitinylation and proteasomal degradation of the receptor
Immunosuppressive and anti-angiogenic sphingosine 1-phosphate receptor-1 agonists induce ubipuitinylation and proteasomal degradation of the receptor
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DOI：
10.1074/jbc.m610318200
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发表时间：
2007-03-23
影响因子：
4.8
通讯作者：
Hla, Timothy
中科院分区：
文献类型：
--
作者：
Oo, Myat Lin;Thangada, Shobha;Hla, Timothy
1-磷酸鞘氨醇（SIP）是一种多功能脂质介质，通过激活SIP 1受体调节淋巴细胞运输、血管通透性和血管生成。该受体被FTY 720-P激活，FTY 720-P是免疫抑制剂和血管活性化合物FTY 720的磷酸化衍生物。然而，与天然配体SIP相比，FTY 720-P似乎作为功能性拮抗剂，即使所涉及的机制知之甚少。在这项研究中，我们研究了内源性表达的SIP 1受体的激动剂激活的人脐静脉内皮细胞和人胚肾293细胞表达绿色荧光蛋白标记的SIP 1的命运。我们表明FTY 720-P在诱导受体降解方面比SIP更有效。用S1 P（1）拮抗剂VPC 44116预处理可阻止受体内化和降解。FTY 720-P没有诱导降解的内化缺陷型SIP 1受体突变体。此外，小干扰RNA介导的G蛋白偶联受体激酶-2和β-arrestins的下调废除FTY 720-P诱导的SIP 1受体降解。这些数据表明，激动剂诱导的SIP 1磷酸化和随后的内吞作用是FTY 720-P诱导的受体降解所必需的。蛋白酶体抑制剂MG 132可阻断S1 P（1）的降解。事实上，FTY 720-P强烈诱导SIP 1受体的多聚泛素化，而诱导完全内化的浓度的SIP不那么有效，表明受体内化是必需的，但不足以泛素化和降解。我们认为FTY 720-P靶向S1 P（1）受体的泛素化和蛋白酶体降解途径的能力可能至少是其免疫抑制和抗血管生成特性的部分基础。
Sphingosine 1-phosphate (SIP), a multifunctional lipid mediator, regulates lymphocyte trafficking, vascular permeability, and angiogenesis by activation of the SIP1 receptor. This receptor is activated by FTY720-P, a phosphorylated derivative of the immunosuppressant and vasoactive compound FTY720. However, in contrast to the natural ligand SIP, FTY720-P appears to act as a functional antagonist, even though the mechanisms involved are poorly understood. In this study, we investigated the fate of endogenously expressed SIP1 receptor in agonist-activated human umbilical vein endothelial cells and human embryonic kidney 293 cells expressing green fluorescent protein-tagged SIP1. We show that FTY720-P is more potent than SIP at inducing receptor degradation. Pretreatment with an antagonist of S1P(1), VPC 44116, prevented receptor internalization and degradation. FTY720-P did not induce degradation of internalization-deficient SIP1 receptor mutants. Further, small interfering RNA-mediated down-regulation of G protein-coupled receptor kinase-2 and beta-arrestins abolished FTY720-P-induced SIP1 receptor degradation. These data suggest that agonist-induced phosphorylation of SIP1 and subsequent endocytosis are required for FTY720-P-induced degradation of the receptor. S1P(1) degradation is blocked by MG132, a proteasomal inhibitor. Indeed, FTY720-P strongly induced polyubiquitinylation of SIP1 receptor, whereas SIP at concentrations that induced complete internalization was not as efficient, suggesting that receptor internalization is required but not sufficient for ubiquitinylation and degradation. We propose that the ability of FTY720-P to target the S1P(1) receptor to the ubiquitinylation and proteasomal degradation pathway may at least in part underlie its immunosuppressive and anti-angiogenic properties.