Institute for Immunology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hanover, Germany.
J Cell Biochem. 2010 Apr 15;109(6):1232-43. doi: 10.1002/jcb.22507.
Sphingosine 1-phosphate (S1P) in blood is phosphorylated, stored, and transported by red blood cells (RBC). Release of S1P from RBC into plasma is a regulated process that does not occur in plasma- or serum-free media. Plasma fractionation and incubations with isolated and recombinant proteins identified high density lipoprotein (HDL) and serum albumin (SA) as non-redundant endogenous triggers for S1P release from RBC. S1P bound to SA and HDL was able to stimulate the S1P(1) receptor in calcium flux experiments. The binding capability of acceptor molecules triggers S1P release, as demonstrated with the anti-S1P antibody Sphingomab. More S1P was extracted from RBC membranes by HDL than by SA. Blood samples from anemic patients confirmed a reduced capacity for S1P release in plasma. In co-cultures of RBC and endothelial cells (EC), we observed transcellular transportation of S1P as a second function of RBC-associated S1P in the absence of SA and HDL and during tight RBC-EC contact, mimicking conditions in tissue interstitium and capillaries. In contrast to S1P bound to SA and HDL, RBC-associated S1P was significantly incorporated by EC after S1P lyase (SGPL1) inhibition. RBC-associated S1P, therefore, has two functions: (1) It contributes to the cellular pool of SGPL1-sensitive S1P in tissues after transcellular transportation and (2) it helps maintain extracellular S1P levels via SA and HDL independently from SGPL1 activity.
血液中的鞘氨醇 1-磷酸（S1P）由红细胞（RBC）磷酸化、储存和转运。S1P 从 RBC 释放到血浆中是一个受调控的过程，不会发生在无血浆或血清的培养基中。血浆分离和与分离的重组蛋白孵育，鉴定出高密度脂蛋白（HDL）和血清白蛋白（SA）是 RBC 中 S1P 释放的非冗余内源性触发物。与 SA 和 HDL 结合的 S1P 能够在钙流实验中刺激 S1P（1）受体。如抗 S1P 抗体 Sphingomab 所示，受体分子的结合能力触发 S1P 释放。HDL 比 SA 从 RBC 膜中提取更多的 S1P。来自贫血患者的血液样本证实了 S1P 在血浆中的释放能力降低。在 RBC 和内皮细胞（EC）的共培养物中，我们观察到 S1P 的跨细胞转运，这是 RBC 相关 S1P 的第二个功能，在没有 SA 和 HDL 以及在 RBC-EC 紧密接触的情况下，模拟组织间质和毛细血管中的条件。与与 SA 和 HDL 结合的 S1P 相比，在 S1P 裂解酶（SGPL1）抑制后，RBC 相关的 S1P 被 EC 显著摄取。因此，RBC 相关的 S1P 具有两个功能：（1）它有助于 SGPL1 敏感的 S1P 在跨细胞转运后在组织中的细胞池；（2）它有助于通过 SA 和 HDL 维持细胞外 S1P 水平，而不依赖于 SGPL1 活性。
