The Lectin Chaperone Calnexin Is Involved in the Endoplasmic Reticulum Stress Response by Regulating Ca2+ Homeostasis in Aspergillus nidulans
The Lectin Chaperone Calnexin Is Involved in the Endoplasmic Reticulum Stress Response by Regulating Ca2+ Homeostasis in Aspergillus nidulans
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凝集素伴侣钙连接蛋白通过调节构巢曲霉的 Ca2 稳态参与内质网应激反应
DOI：
10.1128/aem.00673-17
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发表时间：
2017-05
影响因子：
4.4
通讯作者：
Zhang Shizhu
中科院分区：
文献类型：
--
作者：
Zhang Shenghua;Zheng Hailin;Chen Qiuyi;Chen Yuan;Wang Sha;Lu Ling;Zhang Shizhu
摘要钙离子介导的信号转导途径是真菌适应环境的重要途径。在这里，我们表明，钙连接蛋白，位于内质网（ER）的分子伴侣，起着重要的作用，在调节胞浆游离钙浓度（[Ca 2 +]c）构巢曲霉。钙连接蛋白（ClxA）在A.在内质网胁迫诱导剂二硫苏糖醇（DTT）或高温胁迫下，nidulans的菌丝生长和产孢受到严重影响。重要的是，ΔclxA突变体中的缺陷通过添加细胞外钙而恢复。此外，CchA/MidA复合物（高亲和力Ca 2+通道）、钙调磷酸酶（钙/钙调素依赖性蛋白磷酸酶）和PmrA（分泌途径Ca 2 + ATP酶）是ΔclxA突变体中基于细胞外钙的DTT/热应激敏感性恢复所必需的。有趣的是，ΔclxA突变体在低钙条件下表现出显著减少的分生孢子形成和菌丝生长缺陷，这与MidA/CchA突变引起的缺陷相似。此外，在ΔclxA ΔmidA ΔcchA突变体中，表型缺陷进一步加剧，这表明ClxA和MidA/CchA在钙限制条件下都是必需的。使用钙敏感的发光蛋白水母发光蛋白来监测活细胞中的[Ca 2 +]c，我们发现ClxA和MidA/CchA复合物协同协调响应于细胞外钙的[Ca 2 +]c的瞬时增加。此外，ClxA，特别是它的管腔结构域，在介导响应于DTT诱导的ER应激的瞬时[Ca 2 +]c中起作用，表明ClxA可以介导从内部钙储存释放钙。我们的研究结果提供了新的见解钙连接蛋白在真菌内质网应激适应钙介导的反应的调节作用。重要性钙连接蛋白是一种众所周知的分子伴侣，从酵母到人类都是保守的。虽然它含有钙结合结构域，但对钙连接蛋白在钙调节中的作用知之甚少。在这项研究中，我们表明，钙连接蛋白（ClxA）在丝状真菌构巢曲霉，类似于高亲和力的钙吸收系统（HACS），是所需的正常生长和分生孢子的钙限制条件下。ClxA功能障碍降低了由高细胞外钙或DTT诱导的ER应激诱导的瞬时胞浆游离钙浓度（[Ca 2 +]c）。我们的研究结果提供了直接的证据，钙连接蛋白发挥重要作用，在调节Ca 2+稳态，除了作为一个分子伴侣在真菌中的作用。这些结果为钙连接蛋白的作用提供了新的见解，并扩展了真菌胁迫适应的知识。
ABSTRACT The Ca2+-mediated signaling pathway is crucial for environmental adaptation in fungi. Here we show that calnexin, a molecular chaperone located in the endoplasmic reticulum (ER), plays an important role in regulating the cytosolic free calcium concentration ([Ca2+]c) in Aspergillus nidulans. Inactivation of calnexin (ClxA) in A. nidulans caused severe defects in hyphal growth and conidiation under ER stress caused by the ER stress-inducing agent dithiothreitol (DTT) or high temperature. Importantly, defects in the ΔclxA mutant were restored by the addition of extracellular calcium. Furthermore, the CchA/MidA complex (the high-affinity Ca2+ channels), calcineurin (calcium/calmodulin-dependent protein phosphatase), and PmrA (secretory pathway Ca2+ ATPase) were required for extracellular calcium-based restoration of the DTT/thermal stress sensitivity in the ΔclxA mutant. Interestingly, the ΔclxA mutant exhibited markedly reduced conidium formation and hyphal growth defects under the low-calcium condition, which is similar to defects caused by mutations in MidA/CchA. Moreover, the phenotypic defects were further exacerbated in the ΔclxA ΔmidA ΔcchA mutant, which suggested that ClxA and MidA/CchA are both required under the calcium-limiting condition. Using the calcium-sensitive photoprotein aequorin to monitor [Ca2+]c in living cells, we found that ClxA and MidA/CchA complex synergistically coordinate transient increase in [Ca2+]c in response to extracellular calcium. Moreover, ClxA, in particular its luminal domain, plays a role in mediating the transient [Ca2+]c in response to DTT-induced ER stress in the absence of extracellular calcium, indicating ClxA may mediate calcium release from internal calcium stores. Our findings provide new insights into the role of calnexin in the regulation of calcium-mediated response in fungal ER stress adaptation. IMPORTANCE Calnexin is a well-known molecular chaperone conserved from yeast to humans. Although it contains calcium binding domains, little is known about the role of calnexin in Ca2+ regulation. In this study, we demonstrate that calnexin (ClxA) in the filamentous fungus Aspergillus nidulans, similar to the high-affinity calcium uptake system (HACS), is required for normal growth and conidiation under the calcium-limiting condition. The ClxA dysfunction decreases the transient cytosolic free calcium concentration ([Ca2+]c) induced by a high extracellular calcium or DTT-induced ER stress. Our findings provide the direct evidence that calnexin plays important roles in regulating Ca2+ homeostasis in addition to its role as a molecular chaperone in fungi. These results provide new insights into the roles of calnexin and expand knowledge of fungal stress adaptation.
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影响因子：
4.5
作者：
Zhang Y;Zheng Q;Sun C;Song J;Gao L;Zhang S;Muñoz A;Read ND;Lu L
通讯作者：
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DOI：
10.1083/jcb.200203052
发表时间：
2002-06-10
期刊：
The Journal of cell biology
影响因子：
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通讯作者：
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DOI：
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期刊：
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影响因子：
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影响因子：
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