Healy Luke M, Sheridan Graham K, Pritchard Adam J, Rutkowska Aleksandra, Mullershausen Florian, Dev Kumlesh K
Molecular Neuropharmacology, Department of Physiology, School of Medicine, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland.
Br J Pharmacol. 2013 Jul;169(5):1114-29. doi: 10.1111/bph.12207.
The sphingosine 1-phosphate receptor subtype 1 (S1P1R) is modulated by phosphorylated FTY720 (pFTY720), which causes S1P1R internalization preventing lymphocyte migration thus limiting autoimmune response. Studies indicate that internalized S1P1Rs continue to signal, maintaining an inhibition of cAMP, thus raising question whether the effects of pFTY720 are due to transient initial agonism, functional antagonism and/or continued signalling. To further investigate this, the current study first determined if continued S1P1R activation is pathway specific.
Using human and rat astrocyte cultures, the effects of S1P1R activation on cAMP, pERK and Ca(2+) signalling was investigated. In addition, to examine the role of S1P1R redistribution on these events, a novel biologic (MNP301) that prevented pFTY720-mediated S1P1R redistribution was engineered.
The data showed that pFTY720 induced long-lasting S1P1R redistribution and continued cAMP signalling in rat astrocytes. In contrast, pFTY720 induced a transient increase of Ca(2+) in astrocytes and subsequent antagonism of Ca(2+) signalling. Notably, while leaving pFTY720-induced cAMP signalling intact, the novel MNP301 peptide attenuated S1P1R-mediated Ca(2+) and pERK signalling in cultured rat astrocytes.
These findings suggested that pFTY720 causes continued cAMP signalling that is not dependent on S1P1R redistribution and induces functional antagonism of Ca(2+) signalling after transient stimulation. To our knowledge, this is the first report demonstrating that pFTY720 causes continued signalling in one pathway (cAMP) versus functional antagonism of another pathway (Ca(2+)) and which also suggests that redistributed S1P1Rs may have differing signalling properties from those expressed at the surface.
1-磷酸鞘氨醇受体1型（S1P1R）受磷酸化FTY720（pFTY720）调控，pFTY720可导致S1P1R内化，阻止淋巴细胞迁移，从而限制自身免疫反应。研究表明，内化的S1P1R持续发出信号，维持对环磷酸腺苷（cAMP）的抑制作用，因此引发了关于pFTY720的作用是否归因于短暂的初始激动、功能拮抗和/或持续信号传导的问题。为进一步研究此问题，本研究首先确定持续的S1P1R激活是否具有途径特异性。
利用人源和大鼠星形胶质细胞培养物，研究S1P1R激活对cAMP、磷酸化细胞外信号调节激酶（pERK）和钙离子（Ca(2+)）信号传导的影响。此外，为研究S1P1R重新分布在这些事件中的作用，设计了一种新型生物制剂（MNP301），其可阻止pFTY720介导的S1P1R重新分布。
数据显示，pFTY720在大鼠星形胶质细胞中诱导了持久的S1P1R重新分布和持续的cAMP信号传导。相比之下，pFTY720在星形胶质细胞中诱导了Ca(2+)的短暂增加以及随后对Ca(2+)信号传导的拮抗作用。值得注意的是，新型MNP301肽在不影响pFTY720诱导的cAMP信号传导的情况下，减弱了培养的大鼠星形胶质细胞中S1P1R介导的Ca(2+)和pERK信号传导。
这些发现表明，pFTY720导致持续的cAMP信号传导，该信号传导不依赖于S1P1R重新分布，并在短暂刺激后诱导Ca(2+)信号传导的功能拮抗。据我们所知，这是第一份证明pFTY720在一条途径（cAMP）中导致持续信号传导而在另一条途径（Ca(2+)）中产生功能拮抗的报告，这也表明重新分布的S1P1R可能具有与表面表达的S1P1R不同的信号特性。
