Cellular homeostasis is essential for healthy functioning of cells and tissues as well as proper organ development and maintenance. A disruption in cellular homeostasis triggers stress responses including the unfolded protein response (UPR), an endoplasmic reticulum (ER) stress coping response. There is increasing evidence that Ca^2 + signaling plays a pivotal role in stress responses, as Ca^2 + is involved many cellular activities. The ER is the main Ca^2 + storage organelle and the source of Ca^2 + for intracellular signaling. The ER is equipped with a variety of stress sensors and contains many Ca^2 + handling proteins that support a role for Ca^2 + in stress sensing and in coordinating strategies required to cope with cellular stress. Maintenance of ER Ca^2 + homeostasis is therefore vital in sustaining cellular functions especially during times of cellular stress. Here we focus on selected aspects of ER Ca^2 + homeostasis, its links to ER stress, and activation of the ER stress coping response.

细胞稳态对于细胞和组织的健康功能以及器官的正常发育和维护至关重要。细胞稳态的破坏会引发应激反应，包括未折叠蛋白反应 (UPR)、内质网 (ER) 应激应对反应。越来越多的证据表明，Ca ^{2  +}信号传导在应激反应中起关键作用，因为 Ca ^{2  +}涉及许多细胞活动。ER是主要的Ca ^{2  +}储存细胞器和细胞内信号传导的Ca ^{2  +}来源。ER 配备了多种压力传感器，并包含许多支持 Ca 作用的 Ca ^{2  +}处理蛋白^{2  +}在压力感应和协调应对细胞压力所需的策略方面。因此，维持ER Ca ^{2  +}稳态对于维持细胞功能至关重要，尤其是在细胞应激期间。在这里，我们专注于 ER Ca ^{2  +}稳态的选定方面，它与 ER 应激的联系，以及 ER 应激应对反应的激活。