Zinc enhances adiponectin oligomerization to octadecamers but decreases the rate of disulfide bond formation
Zinc enhances adiponectin oligomerization to octadecamers but decreases the rate of disulfide bond formation
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DOI：
10.1007/s10534-012-9519-9
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发表时间：
2012-04-01
期刊：
影响因子：
3.5
通讯作者：
Tsao, Tsu-Shuen
中科院分区：
文献类型：
--
作者：
Briggs, David B.;Giron, Rebecca M.;Tsao, Tsu-Shuen
脂联素是一种由脂肪细胞分泌的激素，已被证明可以防止胰岛素抵抗、缺血再灌注损伤和炎症的发展。脂联素组装成多种寡聚异构体：三聚体、六聚体和几种高分子量（HMW）物质。其中，HMW物质在2型糖尿病发作期间选择性减少。尽管高分子量脂联素在胰岛素应答中起着关键作用，但其组装过程仍知之甚少。在这份报告中，我们研究了二价阳离子在脂联素组装中的作用。纯化的脂联素18聚体（最大的HMW物质）在用高浓度EDTA处理后未塌陷为较小的低聚体。然而，用EDTA或另一种螯合剂DTPA处理抑制了体外三聚体的18聚体的寡聚化。与Cu ~（2+）、Mg ~（2+）和Ca ~（2+）相比，Zn ~（2+）特异性地增加了18聚体的形成。锌螯合剂TPEN处理的大鼠脂肪细胞分泌的脂联素寡聚体的分布偏向于六聚体和三聚体比例增加。虽然我们观察到从小牛血清中纯化的脂联素中存在锌，但检查了锌在寡聚体之间的二硫键中的作用，因为该过程对于18聚体组装至关重要。令人惊讶的是，Zn 2+抑制二硫键的形成早在低聚过程中。我们推测，二硫键形成速率的初始降低可能会使脂联素亚基在被锁定在不能进一步寡聚化的完全氧化构象之前发生缔合。这些数据表明，锌刺激高分子量脂联素的寡聚化和可能的其他二硫键依赖性蛋白质组装过程。
Adiponectin, a hormone secreted from adipocytes, has been shown to protect against development of insulin resistance, ischemia-reperfusion injury, and inflammation. Adiponectin assembles into multiple oligomeric isoforms: trimers, hexamers and several higher molecular weight (HMW) species. Of these, the HMW species are selectively decreased during the onset of type 2 diabetes. Despite the critical role of HMW adiponectin in insulin responsiveness, its assembly process is poorly understood. In this report, we investigated the role of divalent cations in adiponectin assembly. Purified adiponectin 18mers, the largest HMW species, did not collapse to smaller oligomers after treatment with high concentrations of EDTA. However, treatment with EDTA or another chelator DTPA inhibited the oligomerization of 18mers from trimers in vitro. Zn2+ specifically increased the formation of 18mers when compared with Cu2+, Mg2+, and Ca2+. Distribution of adiponectin oligomers secreted from zinc chelator TPEN-treated rat adipocytes skewed toward increased proportions of hexamers and trimers. While we observed presence of zinc in adiponectin purified from calf serum, the role of zinc in disulfide bonding between oligomers was examined because the process is critical for 18mer assembly. Surprisingly, Zn2+ inhibited disulfide bond formation early in the oligomerization process. We hypothesize that initial decreases in disulfide formation rates could allow adiponectin subunits to associate before becoming locked in fully oxidized conformations incapable of further oligomerization. These data demonstrate that zinc stimulates oligomerization of HMW adiponectin and possibly other disulfide-dependent protein assembly processes.