Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Biología Celular y Molecular, Buenos Aires, Argentina.
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad de Buenos Aires, Instituto de Química y Fisicoquímica Biológicas (IQUIFIB), Buenos Aires, Argentina.
PLoS One. 2019 Mar 21;14(3):e0213917. doi: 10.1371/journal.pone.0213917. eCollection 2019.
Sphingolipids regulate several aspects of cell behavior and it has been demonstrated that cells adjust their sphingolipid metabolism in response to metabolic needs. Particularly, sphingosine-1-phosphate (S1P), a final product of sphingolipid metabolism, is a potent bioactive lipid involved in the regulation of various cellular processes, including cell proliferation, cell migration, actin cytoskeletal reorganization and cell adhesion. In previous work in rat renal papillae, we showed that sphingosine kinase (SK) expression and S1P levels are developmentally regulated and control de novo sphingolipid synthesis. The aim of the present study was to evaluate the participation of SK/S1P pathway in the triggering of cell differentiation by external hypertonicity. We found that hypertonicity evoked a sharp decrease in SK expression, thus activating the de novo sphingolipid synthesis pathway. Furthermore, the inhibition of SK activity evoked a relaxation of cell-cell adherens junction (AJ) with accumulation of the AJ complex (E-cadherin/β-catenin/α-catenin) in the Golgi complex, preventing the acquisition of the differentiated cell phenotype. This phenotype alteration was a consequence of a sphingolipid misbalance with an increase in ceramide levels. Moreover, we found that SNAI1 and SNAI2 were located in the cell nucleus with impairment of cell differentiation induced by SK inhibition, a fact that is considered a biochemical marker of epithelial to mesenchymal transition. So, we suggest that the expression and activity of SK1, but not SK2, act as a control system, allowing epithelial cells to synchronize the various branches of sphingolipid metabolism for an adequate cell differentiation program.
鞘脂类调节细胞行为的多个方面，并且已经证明细胞根据代谢需求来调节其鞘脂代谢。特别是，鞘氨醇-1-磷酸（S1P），是鞘脂代谢的最终产物，是一种参与调节多种细胞过程的生物活性脂质，包括细胞增殖、细胞迁移、肌动蛋白细胞骨架重排和细胞黏附。在我们之前在大鼠肾乳头的研究中，我们表明鞘氨醇激酶（SK）的表达和 S1P 水平受到发育调控，并控制新合成的鞘脂合成。本研究的目的是评估 SK/S1P 途径在外部高渗性触发细胞分化中的参与作用。我们发现高渗性引起 SK 表达的急剧下降，从而激活新合成的鞘脂合成途径。此外，SK 活性的抑制会引起细胞-细胞黏附连接（AJ）的松弛，AJ 复合物（E-钙黏蛋白/β-连环蛋白/α-连环蛋白）在高尔基体中积累，阻止获得分化细胞表型。这种表型改变是鞘脂失衡的结果，导致神经酰胺水平增加。此外，我们发现 SNAI1 和 SNAI2 位于细胞核中，SK 抑制诱导的细胞分化受损，这一事实被认为是上皮细胞向间充质转化的生化标志物。因此，我们认为 SK1 的表达和活性是一种控制系统，允许上皮细胞同步鞘脂代谢的各个分支，以实现适当的细胞分化程序。
