Exosome-dependent trafficking of HSP70 - A novel secretory pathway for cellular stress proteins
Exosome-dependent trafficking of HSP70 - A novel secretory pathway for cellular stress proteins
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DOI：
10.1074/jbc.m502017200
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发表时间：
2005-06-17
影响因子：
4.8
通讯作者：
Febbraio, MA
中科院分区：
文献类型：
--
作者：
Lancaster, GI;Febbraio, MA
热休克蛋白（HSPs）是在所有真核生物和原核生物中发现的细胞内蛋白质家族。它们的功能被很好地表征，并且是维持细胞稳态和促进细胞存活以响应应激细胞条件的核心。然而，一些研究提供的证据表明，HSP家族的特定成员可能是通过一个未知的胞吐途径分泌。在这里，我们表明，外泌体，由许多细胞类型分泌的小膜囊泡，有助于从人外周血单核细胞（PBMC）在基础和应激诱导（40或43 ℃热休克1小时）状态下释放HSP 70。HSP 70从PBMC的释放是独立的共同的分泌途径，因为布雷菲德菌素A，经典的蛋白质转运途径的抑制剂，不阻断HSP 70的释放。此外，我们表明HSP 70从PBMC的释放不通过脂筏依赖性途径发生，因为用甲基-β-环糊精（一种筏破坏药物）处理对HSP 70释放没有影响。为了检查外泌体是否有助于从PBMC释放HSP 70，从PBMC培养物纯化外泌体，并测定外泌体数量和HSP 70含量。我们证明，虽然热休克不影响外泌体的分泌速率，但从热休克PBMC分离的外泌体的HSP 70含量显著高于对照。这些数据确定了一种新的分泌途径，HSP 70可以主动释放的细胞在基础和应力诱导状态。
The heat shock proteins (HSPs) are a family of intracellular proteins found in all eukaryotes and prokaryotes. Their functions are well characterized and are central to maintaining cellular homeostasis and in promoting cell survival in response to stressful cellular conditions. However, several studies provide evidence that specific members of the HSP family might be secreted via an unidentified exocytotic pathway. Here we show that exosomes, small membrane vesicles that are secreted by numerous cell types, contribute to the release of HSP70 from human peripheral blood mononuclear cells (PBMCs) in both basal and stress-induced (heat shock at 40 or 43 C for 1 h) states. HSP70 release from PBMCs is independent of the common secretory pathway because Brefeldin A, an inhibitor of the classical protein transport pathway, did not block HSP70 release. Furthermore, we show that HSP70 release from PBMCs does not occur via a lipid raft- dependent pathway, because treatment with methyl-beta-cyclodextrin, a raft-disrupting drug, had no affect on HSP70 release. To examine whether exosomes contributed to HSP70 release from PBMCs, exosomes were purified from PBMC cultures, and exosomal number and HSP70 content were determined. We demonstrate that although heat shock does not influence the exosomal secretory rate, the HSP70 content of exosomes isolated from heat shocked PBMCs is significantly higher than control. These data identify a novel secretory pathway by which HSP70 can be actively released from cells in both the basal and stress-induced state.