Lateral Segregation of Palmitoyl Ceramide-1-Phosphate in Simple and Complex Bilayers
Lateral Segregation of Palmitoyl Ceramide-1-Phosphate in Simple and Complex Bilayers
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DOI：
10.1016/j.bpj.2019.05.015
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发表时间：
2019-07-09
影响因子：
3.4
通讯作者：
Slotte, J. Peter
中科院分区：
文献类型：
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作者：
Al Sazzad, Md Abdullah;Yasuda, Tomokazu;Slotte, J. Peter
神经酰胺-1-磷酸是一种次要的鞘脂，在细胞信号传导中起重要作用。在这项研究中，我们研究了棕榈酰神经酰胺-1-磷酸（Cer-1P）在23℃和37℃下以不同的双分子层组成向有序结构域横向分离的倾向，并将其与棕榈酰神经酰胺（PCer）和棕榈酰鞘磷脂（PSM）的分离进行了比较。利用反式氨基甲酸的发射寿命变化和差示扫描量热图确定了液体磷脂酰胆碱双分子层中有序结构域的形成。当在Tris缓冲液（50 mM Tris, 140 mM NaCl (pH 7.4)）中水合成双层时，检测了Cer-1P的侧向偏析。在这个pH下，Cer-1P带负电。Cer-1P在1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（POPC）双分子层中的侧向分离倾向介于PCer和PSM之间。通过差示扫描量热分析，我们发现，在相同成分（熔化范围为20 ~ 55℃）的情况下，由Cer-1P在POPC双层中形成的凝胶结构域（POPC: Cer-1P 70:30 by mol）比对应的POPC和PCer凝胶结构域更不稳定（熔化范围为16 ~ 37℃）。凝胶相熔化焓在Cer-1P （1.5 kcal/mol）中也远低于含有pcer的POPC双层（9 kcal/mol）。在POPC双层结构中，Cer-1P似乎至少部分与pcp结构域可混溶。在PSM存在下，Cer-1P结构域稳定（POPC: PSM 85: 15），与pcer -富结构域相似。在37℃的双分子层中，具有近似的外小叶细胞膜组成（鞘磷脂和胆固醇富集，氨基磷脂缺乏），Cer-1P分离不会导致有序结构域的形成，至少与PCer分离相比是这样。在近似内小叶组成的双分子层中（鞘磷脂缺乏，胆固醇和氨基磷脂富集），Cer-1P也不能形成有序结构域。只有当PCer/胆固醇比超过近似等摩尔比时，PCer才会分离成有序结构域。
Ceramide-1-phosphate is a minor sphingolipid with important functions in cell signaling. In this study, we examined the propensity of palmitoyl ceramide-1-phosphate (Cer-1P) to segregate laterally into ordered domains in different bilayer compositions at 23 and 37 degrees C and compared this with segregation of palmitoyl ceramide (PCer) and palmitoyl sphingomyelin (PSM). The ordered-domain formation in the fluid phosphatidylcholine bilayers was determined using the emission lifetime changes of trans-parinaric acid and from differential scanning calorimetry thermograms. The lateral segregation of Cer-1P was examined when hydrated to bilayers in Tris buffer (50 mM Tris, 140 mM NaCl (pH 7.4)). At this pH, Cer-1P was negatively charged. The lateral segregation propensity of Cer-1P in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers was intermediate between PCer and PSM. Based on differential scanning calorimetry analysis, we observed that the gel domains formed by Cer-1P in POPC bilayers (POPC: Cer-1P 70:30 by mol) were less stable (melting interval 16-37 degrees C) than the corresponding POPC and PCer gel domains at equal composition (melting interval 20-55 degrees C). The gel-phase melting enthalpy was also much lower in Cer-1P (1.5 kcal/mol) than in the PCer-containing POPC bilayers (9 kcal/mol). Cer-1P appeared to be at least partially miscible with PCer domains in POPC bilayers. Cer-1P domains were stabilized in the presence of PSM (POPC: PSM 85: 15), similarly as seen with PCer-rich domains. In bilayers at 37 degrees C, with an approximate outer-leaflet cell membrane composition (sphingomyelin and cholesterol enriched, aminophospholipid poor), Cer-1P segregation did not lead to the formation of ordered domains, at least when compared with PCer segregation. In bilayers with an approximate inner-leaflet composition (sphingomyelin poor, cholesterol and aminophospholipid enriched), Cer-1P also failed to form ordered domains. PCer segregated into ordered domains only after the PCer/cholesterol ratio exceeded an approximate equimolar ratio.