Functional specialization of calreticulin domains.
Functional specialization of calreticulin domains.
复制标题
钙网蛋白结构域的功能专业化。
DOI：
10.1083/jcb.200102073
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发表时间：
2001-09-03
影响因子：
7.8
通讯作者：
Michalak, M
中科院分区：
文献类型：
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作者：
Nakamura, K;Zuppini, A;Arnaudeau, S;Lynch, J;Ahsan, I;Krause, R;Papp, S;De Smedt, H;Parys, J B;Muller-Esterl, W;Lew, D P;Krause, K H;Demaurex, N;Opas, M;Michalak, M
钙网蛋白是内质网（ER）中的Ca2+结合伴侣，钙网蛋白基因敲除是胚胎致命的。在这里，我们使用钙网蛋白缺乏的小鼠胚胎成纤维细胞来研究钙网蛋白作为Ca2+稳态调节剂的功能。在没有钙调钙蛋白的细胞中，内质网具有较低的Ca2+储存能力，尽管游离内质网腔内Ca2+浓度不变。钙网蛋白缺乏的细胞在缓激肽的作用下显示Ca2+释放受到抑制，但它们在肌醇1,4,5-三磷酸（InsP3）的直接激活下释放Ca2+。这些细胞在缓激肽刺激下不能产生可测量水平的InsP3，可能是因为缓激肽与其细胞表面受体的结合受损。缓激肽结合和缓激肽诱导的Ca2+释放都是通过全长钙网蛋白和蛋白的N + P结构域的表达来恢复的。钙调钙蛋白的P + C结构域的表达不影响缓激肽诱导的Ca2+释放，但恢复内质网Ca2+储存能力。我们的研究结果表明，钙网蛋白可能在缓激肽受体的折叠中发挥作用，从而影响其在钙网蛋白缺乏的细胞中启动insp3依赖性Ca2+释放的能力。我们认为钙钙蛋白的C结构域在Ca2+储存中起作用，而N结构域可能参与其伴侣蛋白的功能。
Calreticulin is a Ca2+-binding chaperone in the endoplasmic reticulum (ER), and calreticulin gene knockout is embryonic lethal. Here, we used calreticulin-deficient mouse embryonic fibroblasts to examine the function of calreticulin as a regulator of Ca2+ homeostasis. In cells without calreticulin, the ER has a lower capacity for Ca2+ storage, although the free ER luminal Ca2+ concentration is unchanged. Calreticulin-deficient cells show inhibited Ca2+ release in response to bradykinin, yet they release Ca2+ upon direct activation with the inositol 1,4,5-trisphosphate (InsP3). These cells fail to produce a measurable level of InsP3 upon stimulation with bradykinin, likely because the binding of bradykinin to its cell surface receptor is impaired. Bradykinin binding and bradykinin-induced Ca2+ release are both restored by expression of full-length calreticulin and the N + P domain of the protein. Expression of the P + C domain of calreticulin does not affect bradykinin-induced Ca2+ release but restores the ER Ca2+ storage capacity. Our results indicate that calreticulin may play a role in folding of the bradykinin receptor, which affects its ability to initiate InsP3-dependent Ca2+ release in calreticulin-deficient cells. We concluded that the C domain of calreticulin plays a role in Ca2+ storage and that the N domain may participate in its chaperone functions.