Moreau P, Cassagne C, Keenan T W, Morré D J
Institut de Biochimie Cellulaire et Neurochimie, Centre National de la Recherche Scientifique, Bordeaux, France.
Biochim Biophys Acta. 1993 Feb 23;1146(1):9-16. doi: 10.1016/0005-2736(93)90332-t.
The distribution and cell-free transfer of ceramide and other lipids were compared using highly purified fractions of endoplasmic reticulum, transitional endoplasmic reticulum, transition vesicles and Golgi apparatus from rat liver. Ceramides were present in both endoplasmic reticulum and Golgi apparatus where they represented between 0.3 and 1% of the total lipids. Ceramides, however, were much reduced or absent (< 0.05%) from transition vesicles. Transition vesicles were induced to form from transitional endoplasmic reticulum by incubation with ATP and a cytosol fraction. When transfer of [14C]choline-labeled phosphatidylcholine from transitional endoplasmic reticulum to Golgi apparatus was followed, transition vesicles were more efficient in transfer than the transitional endoplasmic reticulum from which they were derived. This transfer was temperature- and ATP-dependent and inhibited by N-ethylmaleimide. When transfer of [3H]ceramide was followed, there was little or no transfer via transition vesicles and that transfer which occurred was temperature-, ATP- and N-ethylmaleimide independent. Transfer of ceramide in the cell-free system did occur from endoplasmic reticulum to Golgi apparatus but via a non-vesicular mechanism that was temperature-dependent but not dependent on ATP or cytosol, alone, or in combination, nor was it inhibited by N-ethylmaleimide. A component of phosphatidylcholine transfer exhibited similar characteristics. The results provide evidence for two distinct mechanisms for cell-free transfer of lipids from endoplasmic reticulum to Golgi apparatus. The first is via 50 to 70 nm transition vesicles which is temperature- and ATP-dependent, inhibited by N-ethylmaleimide and from which ceramides are excluded. The second is non-vesicular, temperature-dependent, and neither ATP- nor cytosol-dependent. It accounts for the bulk of the ceramide transfer. As a result during cell-free lipid transfer from endoplasmic reticulum to Golgi apparatus, lipid sorting occurs such that ceramides are largely absent from the transition vesicles and, apparently are delivered to the Golgi apparatus by another mechanism.
利用从大鼠肝脏中高度纯化得到的内质网、过渡内质网、过渡囊泡和高尔基体组分，比较了神经酰胺和其他脂质的分布及无细胞转运情况。神经酰胺在内质网和高尔基体中均有存在，占总脂质的0.3%至1%。然而，过渡囊泡中的神经酰胺含量大幅降低或不存在（<0.05%）。通过与ATP和胞质溶胶组分孵育，诱导过渡内质网形成过渡囊泡。当追踪[14C]胆碱标记的磷脂酰胆碱从过渡内质网到高尔基体的转运时，过渡囊泡比其来源的过渡内质网转运效率更高。这种转运依赖于温度和ATP，并受到N - 乙基马来酰亚胺的抑制。当追踪[3H]神经酰胺的转运时，通过过渡囊泡的转运很少或没有，且发生的转运不依赖于温度、ATP和N - 乙基马来酰亚胺。在无细胞体系中，神经酰胺确实从内质网转运到了高尔基体，但通过一种非囊泡机制，该机制依赖于温度，但不依赖于ATP或胞质溶胶单独或共同作用，也不受N - 乙基马来酰亚胺的抑制。磷脂酰胆碱转运的一个组分表现出类似的特征。这些结果为脂质从内质网到高尔基体的无细胞转运存在两种不同机制提供了证据。第一种是通过50至70纳米的过渡囊泡，其依赖于温度和ATP，受N - 乙基马来酰亚胺抑制，且神经酰胺被排除在外。第二种是非囊泡的，依赖于温度，既不依赖于ATP也不依赖于胞质溶胶。它占神经酰胺转运的大部分。因此，在脂质从内质网到高尔基体的无细胞转运过程中，会发生脂质分选，使得过渡囊泡中基本上没有神经酰胺，显然是通过另一种机制将其递送至高尔基体。
