An essential role for the phosphatidylinositol transfer protein in the scission of coatomer-coated vesicles from the trans-Golgi network.
An essential role for the phosphatidylinositol transfer protein in the scission of coatomer-coated vesicles from the trans-Golgi network.
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DOI：
10.1073/pnas.95.19.11181
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发表时间：
1998-09
影响因子：
11.1
通讯作者：
J. Simon;T. Morimoto;V. Bankaitis;T. Gottlieb;I. Ivanov;M. Adesnik;D. Sabatini
中科院分区：
文献类型：
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作者：
J. Simon;T. Morimoto;V. Bankaitis;T. Gottlieb;I. Ivanov;M. Adesnik;D. Sabatini
我们鉴定了磷脂酰肌醇转移蛋白(PITP)负责一种强大的潜伏的，核苷酸无关的，高尔基体泡囊化活性，这种活性存在于细胞质中，但只在细胞质蛋白亚组分中表现为一种不受控制的活性，在胞质蛋白亚组分中，它与通常似乎限制其作用的调节成分分离，这些调节成分似乎限制其作用于COPI覆盖的芽从跨高尔基网络膜上断裂。识别这两种哺乳动物PITP亚型的特异性抗PITP抗体完全抑制胞浆支持正常囊泡生成的能力，以及胞浆蛋白亚组分所表现出的不受控制的囊泡活性。负载磷脂酰肌醇(PI)的酵母PITP，Sec14p，而不是负载磷脂酰胆碱(PC)的蛋白质，能够替代胞质亚组分，促进被覆的芽从反式高尔基体网络中断裂。然而，在较高浓度时，Sec14p负载PI时，而不是PC或磷脂酰甘油，其本身导致未包被的高尔基膜不分青红皂白的囊泡，PC-Sec14p可以抑制这种囊泡，这也抑制了胞质亚组分引起的不受控制的囊泡。我们认为，通过将PI输送到包被芽颈部附近高尔基体膜上的特定位置，PITP诱导了脂质双层组织的局部变化，可能涉及PI代谢产物，从而触发了高尔基体膜外质面的融合，这是切割COPI包被囊泡所必需的。
We identified the phosphatidylinositol transfer protein (PITP) as being responsible for a powerful latent, nucleotide-independent, Golgi-vesiculating activity that is present in the cytosol but is only manifested as an uncontrolled activity in a cytosolic protein subfraction, in which it is separated from regulatory components that appear to normally limit its action to the scission of COPI-coated buds from trans-Golgi network membranes. A specific anti-PITP antibody that recognizes the two mammalian PITP isoforms fully inhibited the capacity of the cytosol to support normal vesicle generation as well as the uncontrolled vesiculating activity manifested by the cytosolic protein subfraction. The phosphatidylinositol- (PI) loaded form of the yeast PITP, Sec14p, but not the phosphatidylcholine- (PC) loaded form of the protein, was capable of substituting for the cytosolic subfraction in promoting the scission of coated buds from the trans-Golgi network. At higher concentration, however, Sec14p, when loaded with PI, but not with PC or phosphatidylglycerol, caused by itself an indiscriminate vesiculation of uncoated Golgi membranes that could be suppressed by PC-Sec14p, which also suppresses the uncontrolled vesiculation caused by the cytosolic subfraction. We propose that, by delivering PI to specific sites in the Golgi membrane near the necks of coated buds, PITP induces local changes in the organization of the lipid bilayer, possibly involving PI metabolites, that triggers the fusion of the ectoplasmic faces of the Golgi membrane necessary for the scission of COPI-coated vesicles.