Annexin A5 binds to lipopolysaccharide and reduces its endotoxin activity.
Annexin A5 binds to lipopolysaccharide and reduces its endotoxin activity.
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DOI：
10.1128/mbio.00292-11
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发表时间：
2012
期刊：
影响因子：
6.4
通讯作者：
McKitrick JC
中科院分区：
文献类型：
--
作者：
Rand JH;Wu XX;Lin EY;Griffel A;Gialanella P;McKitrick JC
膜联蛋白 A5 (AnxA5) 对磷脂酰丝氨酸具有高亲和力。该蛋白质被广泛用于检测凋亡细胞，因为磷脂酰丝氨酸（一种通常存在于细胞质膜内叶的磷脂）在程序性细胞死亡过程中易位至外叶。在这里，我们报告了 AnxA5 通过脂多糖 (LPS) 的脂质 A 结构域与革兰氏阴性细菌结合的新观察结果。定量测量了 AnxA5 与细菌的结合，并通过荧光显微镜证实，并发现其受到针对脂质 A 的抗体的抑制。AnxA5 还与纯化的点印迹 LPS 和脂质 A 结合。通过椭圆光度法，我们发现 AnxA5 与纯化的 LPS 的结合是钙依赖性的、快速的，并表现出高亲和力——与 AnxA5 与磷脂酰丝氨酸的结合相似的特征。初步功能研究表明 AnxA5 可以影响 LPS 活性。 AnxA5 在鲎阿米巴细胞裂解物测定中抑制 LPS 介导的凝胶化。与单独与 LPS 孵育相比，LPS 与蛋白质一起孵育可减少培养单核细胞释放的肿瘤坏死因子 α (TNF-α) 的数量。最初的体内实验表明，注射与 AnxA5 预孵育的 LPS 的小鼠产生的血清 TNF-α 水平低于单独注射 LPS 后观察到的水平。这些数据表明 AnxA5 与 LPS 结合，并为研究这种相互作用的潜在生物学和治疗意义开辟了道路。 AnxA5 在具有屏障功能的细胞中高表达，其中包括血管内皮细胞、胎盘滋养层细胞以及胆管、肾小管、乳腺导管和鼻上皮细胞。该蛋白质因其与含有磷脂酰丝氨酸的磷脂双层的结合而得到了很好的表征。这份关于 AnxA5 先前未被识别的活性的报告为研究这种结合可能具有生物学和治疗影响的可能性打开了大门。鉴于该蛋白质的组织表达，目前的结果表明AnxA5可能在调节宿主对这些解剖部位（细胞可能与微生物接触的部位）脂多糖的防御中发挥作用。这些结果还提出了一个有趣的可能性，即 AnxA5 或类似的蛋白质或肽可以提供新的方法来解决革兰氏阴性脓毒症这一棘手的临床问题。
Annexin A5 (AnxA5) has a high affinity for phosphatidylserine. The protein is widely used to detect apoptotic cells because phosphatidylserine, a phospholipid that is normally present in the inner leaflets of cytoplasmic membranes, becomes translocated to the outer leaflets during programmed cell death. Here we report the novel observation that AnxA5 binds to Gram-negative bacteria via the lipid A domain of lipopolysaccharide (LPS). Binding of AnxA5 to bacteria was measured quantitatively, confirmed by fluorescence microscopy, and found to be inhibited by antibodies against lipid A. AnxA5 also bound to purified dot-blotted LPS and lipid A. Through ellipsometry, we found that the binding of AnxA5 to purified LPS was calcium dependent and rapid and showed a high affinity—characteristics similar to those of AnxA5 binding to phosphatidylserine. Initial functional studies indicated that AnxA5 can affect LPS activities. AnxA5 inhibited LPS-mediated gelation in the Limulus amebocyte lysate assay. Incubation of LPS with the protein reduced the quantity of tumor necrosis factor alpha (TNF-α) released by cultured monocytes compared to that released upon incubation with LPS alone. Initial in vivo experiments indicated that injection of mice with LPS preincubated with AnxA5 produced serum TNF-α levels lower than those seen after injection of LPS alone. These data demonstrate that AnxA5 binds to LPS and open paths to investigation of the potential biological and therapeutic implications of this interaction. AnxA5 is highly expressed in cells that have a barrier function—including, among others, vascular endothelium, placental trophoblasts, and epithelial cells lining bile ducts, renal tubules, mammary ducts, and nasal epithelium. The protein has been well characterized for its binding to phospholipid bilayers that contain phosphatidylserine. This report of a previously unrecognized activity of AnxA5 opens the door to investigation of the possibility that this binding may have biological and therapeutic ramifications. In view of the tissue expression of the protein, the present results suggest the possibility that AnxA5 plays a role in modulating the host defense against lipopolysaccharide at these anatomic sites, where cells may interface with microorganisms. These results also raise the intriguing possibility that AnxA5 or analogous proteins or peptides could provide novel approaches to addressing the difficult clinical problem of Gram-negative sepsis.