The endoplasmic reticulum (ER) is extensively remodelled during the development of professional secretory cells to cope with high protein production. Since ER is the principal Ca²⁺ store in the cell, we characterised the Ca²⁺ homeostasis in NALM-6 and RPMI 8226 cells, which are commonly used as human pre-B and antibody secreting plasma cell models, respectively. Expression levels of Sec61 translocons and the corresponding Sec61-mediated Ca²⁺ leak from ER, Ca²⁺ storage capacity and store-operated Ca²⁺ entry were significantly enlarged in the secretory RPMI 8226 cell line. Using an immunoglobulin M heavy chain producing HeLa cell model, we found that the enlarged Ca²⁺ storage capacity and Ca²⁺ leak from ER are linked to ER expansion. Our data delineates a developmental remodelling of Ca²⁺ homeostasis in professional secretory cells in which a high Sec61-mediated Ca²⁺ leak and, thus, a high Ca²⁺ turnover in the ER is backed up by enhanced store-operated Ca²⁺ entry.

内质网 (ER) 在专业分泌细胞的发育过程中被广泛改造，以应对高蛋白生产。由于 ER 是细胞中主要的 Ca ²⁺储存，我们表征了 NALM-6 和 RPMI 8226 细胞中的 Ca ²⁺稳态，它们通常分别用作人类前 B 和抗体分泌浆细胞模型。在分泌型 RPMI 8226 细胞系中，Sec61 易位子的表达水平和相应的 Sec61 介导的来自 ER 的 Ca ²⁺泄漏、Ca ²⁺储存容量和储存操作的 Ca ^{2+进入显着增加。}使用产生免疫球蛋白 M 重链的 HeLa 细胞模型，我们发现增大的 Ca ²⁺ER 的储存容量和 Ca ²⁺泄漏与 ER 膨胀有关。我们的数据描绘了专业分泌细胞中 Ca ²⁺稳态的发育重塑，其中高 Sec61 介导的 Ca ²⁺泄漏，因此，ER 中的高 Ca ²⁺周转率得到增强的存储操作 Ca ²⁺的支持入口。