Fatty acid transport protein 2 interacts with ceramide synthase 2 to regulate ceramide synthesis

Dihydroceramide is generated via the action of (dihydro)ceramide synthases (CerSs), which use two substrates, namely sphinganine and fatty acyl CoAs. Sphinganine is generated via the sequential activity of two integral membrane proteins located in the endoplasmic reticulum. Less is known about the source of supply of the fatty acyl CoAs, although a number of cytosolic proteins in the pathways of acyl CoA generation have been shown to modulate ceramide synthesis via direct or indirect interaction with the CerSs. We now demonstrate, by proteomic analysis of immunoprecipitated proteins, that fatty acid transporter protein 2 (FATP2) (also known as very long-chain acyl-CoA synthetase) directly interacts with CerS2 in mouse liver. Studies in cultured cells demonstrated that other members of the FATP family can also interact with CerS2, with the interaction dependent on both proteins being catalytically active. Transfection of cells with FATP1, FATP2 or FATP4 increased ceramide levels although only FATP2 and 4 increased dihydroceramide levels, consistent with their known intracellular locations. Finally, lipofermata, an FATP2 inhibitor which is believed to directly impact tumor cell growth via modulation of FATP2, decreased de novo dihydroceramide synthesis, suggesting that some of the proposed therapeutic effects of lipofermata may actually be mediated via (dihydro)ceramide rather than directly via acyl CoA generation

二氢神经酰胺（dihydroceramide）经由（二氢）神经酰胺合酶（CerSs）的催化作用生成，该酶以神经鞘氨醇（sphinganine）与脂酰辅酶A（fatty acyl CoAs）作为双底物。神经鞘氨醇由定位于内质网（endoplasmic reticulum）的两种整合膜蛋白依次催化产生。目前学界对脂酰辅酶A的供应来源仍知之甚少，尽管已有研究证实，脂酰辅酶A生成通路中的多种胞质蛋白可通过与CerSs发生直接或间接相互作用，进而调控神经酰胺的合成。
本研究通过对免疫沉淀蛋白的蛋白质组学分析证实，脂肪酸转运蛋白2（fatty acid transporter protein 2, FATP2，亦称超长链脂酰辅酶A合成酶（very long-chain acyl-CoA synthetase））可在小鼠肝脏中与CerS2直接相互作用。对培养细胞的研究显示，FATP家族的其他成员同样可与CerS2结合，且该相互作用依赖于两种蛋白均具备催化活性。
将FATP1、FATP2或FATP4转染至细胞后，细胞内神经酰胺水平均有所升高；但仅FATP2与FATP4可提升二氢神经酰胺水平，这与二者已知的细胞内定位相符。
最后，作为一种被认为可通过调控FATP2直接影响肿瘤细胞生长的FATP2抑制剂——脂非马他（lipofermata），可降低二氢神经酰胺的从头合成速率，这提示脂非马他所报道的部分治疗效应，实际上可能是通过（二氢）神经酰胺通路介导，而非直接通过脂酰辅酶A生成途径实现。