Vectorial budding of vesicles by asymmetrical enzymatic formation of ceramide in giant liposomes
Vectorial budding of vesicles by asymmetrical enzymatic formation of ceramide in giant liposomes
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DOI：
10.1016/s0006-3495(00)76640-9
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发表时间：
2000-02-01
影响因子：
3.4
通讯作者：
Kinnunen, PKJ
中科院分区：
文献类型：
--
作者：
Holopainen, JM;Angelova, MI;Kinnunen, PKJ
鞘磷脂是真核细胞膜的丰富成分。鞘磷脂酶是一种特殊的酶，可以将这种脂质转化为神经酰胺，神经酰胺是细胞凋亡（程序性细胞死亡）、分化和衰老的细胞信号传导中的中心第二信使。我们使用显微注射和霍夫曼调制对比或荧光显微镜的巨型脂质体组成的1-硬脂酰-2-油酰-sn-甘油-3-磷酸胆碱（SOPC），N-棕榈酰-鞘磷脂（C16：0-SM），和Bodipy-鞘磷脂作为荧光示踪剂（摩尔比分别为0.75：0.20：0.05），以观察脂质侧向分布和膜形态的变化后，神经酰胺的形成。值得注意的是，除了快速结构域形成（加帽）之外，囊泡的载体出芽，即，内吞作用和脱落可分别由巨大磷脂酰胆碱/鞘磷脂脂质体的外小叶或内小叶中的鞘磷脂酶催化的神经酰胺的不对称产生诱导。这些结果很容易解释为I）富含神经酰胺的结构域的横向相分离，2）相邻单层之间的面积差，3）负自发曲率，和4）含神经酰胺的结构域的增加的弯曲刚度，导致双层的膜内陷和囊泡化。
Sphingomyelin is an abundant component of eukaryotic membranes. A specific enzyme, sphingomyelinase can convert this lipid to ceramide, a central second messenger in cellular signaling for apoptosis (programmed cell death), differentiation, and senescence. We used microinjection and either Hoffman modulation contrast or fluorescence microscopy of giant liposomes composed of 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC), N-palmitoyl-sphingomyelin (C16: 0-SM), and Bodipy-sphingomyelin as a fluorescent tracer (molar ratio 0.75:0.20:0.05, respectively) to observe changes in lipid lateral distribution and membrane morphology upon formation of ceramide. Notably, in addition to rapid domain formation (capping), vectorial budding of vesicles, i.e., endocytosis and shedding, can be induced by the asymmetrical sphingomyelinase-catalyzed generation of ceramide in either the outer or the inner leaflet, respectively, of giant phosphatidylcholine/sphingomyelin liposomes. These results are readily explained by I) the lateral phase separation of ceramide enriched domains, 2) the area difference between the adjacent monolayers, 3) the negative spontaneous curvature, and 4) the augmented bending rigidity of the ceramide-containing domains, leading to membrane invagination and vesiculation of the bilayer.