Fusion of lamellar body with plasma membrane is driven by the dual action of annexin II tetramer and arachidonic acid
Fusion of lamellar body with plasma membrane is driven by the dual action of annexin II tetramer and arachidonic acid
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DOI：
10.1074/jbc.m212594200
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发表时间：
2003-10-10
影响因子：
4.8
通讯作者：
Liu, L
中科院分区：
文献类型：
--
作者：
Chattopadhyay, S;Sun, P;Liu, L
膜联蛋白II参与了肺泡II型上皮细胞板层小体的胞吐过程中的膜融合。以前的大多数研究都是基于模型膜的融合分析。在本研究中，我们利用分离的板层小体和质膜研究了膜联蛋白II介导的膜融合，这是通过十八烷基罗丹明B(R18)的自猝灭来确定的。从II型细胞胞浆中去除膜联蛋白II会降低其融合活性。纯化的膜联蛋白II四聚体(AIIt)以剂量依赖的方式诱导板层小体与质膜的融合。这种融合是钙离子依赖的，并且对AIIt具有高度的特异性，因为其他膜联蛋白(I和II单体、III、IV、V和VI)不能诱导融合。用N-乙基马来酰亚胺、一氧化氮或过氧亚硝酸根修饰AIIt的不同功能残基，可阻断AIIt介导的融合。花生四烯酸促进AIIt介导的融合，并将其对钙的需求降低到细胞内可达到的水平。这种作用是由于膜结合的花生四烯酸，而不是游离的花生四烯酸。其他脂肪酸包括亚麻酸、棕榈油酸、肉豆蔻酸、硬脂酸、棕榈酸和肉豆蔻酸影响不大。AIIt介导的融合被牛血清白蛋白从板层小体和质膜上去除花生四烯酸所抑制。将花生四烯酸重新添加到花生四烯酸耗尽的膜上，恢复了其融合活性。我们的结果表明，板层小体与质膜的融合是由AIIt和花生四烯酸的协同作用推动的。
Annexin II has been implicated in membrane fusion during the exocytosis of lamellar bodies from alveolar epithelial type II cells. Most previous studies were based on the fusion assays by using model membranes. In the present study, we investigated annexin II-mediated membrane fusion by using isolated lamellar bodies and plasma membrane as determined by the relief of octadecyl rhodamine B (R18) self-quenching. Immunodepletion of annexin II from type II cell cytosol reduced its fusion activity. Purified annexin II tetramer (AIIt) induced the fusion of lamellar bodies with the plasma membrane in a dose-dependent manner. This fusion is Ca2+-dependent and is highly specific to AIIt because other annexins (I and II monomer, III, IV, V, and VI) were unable to induce the fusion. Modification of the different functional residues of AIIt by N-ethylmaleimide, nitric oxide, or peroxynitrite abolished AIIt-mediated fusion. Arachidonic acid enhanced AIIt-mediated fusion and reduced its Ca2+ requirement to an intracellularly achievable level. This effect is due to membrane-bound arachidonic acid, not free arachidonic acid. Other fatty acids including linolenic acid, palmitoleic acid, myristoleic acid, stearic acid, palmitic acid, and myristic acid had little effect. AIIt-mediated fusion was suppressed by the removal of arachidonic acid from lamellar body and plasma membrane using bovine serum albumin. The addition of arachidonic acid back to the arachidonic acid-depleted membranes restored its fusion activity. Our results suggest that the fusion between lamellar bodies with the plasma membrane is driven by the synergistic action of AIIt and arachidonic acid.