Morita Takao, Tanimura Akihiko, Baba Yoshihiro, Kurosaki Tomohiro, Tojyo Yosuke
Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan.
J Med Invest. 2009;56 Suppl:383-7. doi: 10.2152/jmi.56.383.
In most non-excitable cells, the depletion of intracellular Ca(2+) stores activates capacitative Ca(2+) entry (CCE), which is a Ca(2+)-selective and La(3+)-sensitive entry pathway. Here, we report a novel mechanism of La(3+)-resistant Ca(2+) entry that is synergistically regulated by B cell receptor (BCR) stimulation and Ca(2+) store depletion (B-SOC). In the wild-type (WT) DT40 cells, BCR stimulation with anti-IgM antibodies induced Ca(2+) release and subsequent Ca(2+) entry in the presence of 0.3 microM La(3+) which blocks CCE completely. In the inositol 1,4,5-trisphosphate receptor-deficient (IP(3)R-KO) cells, BCR stimulation elicited neither Ca(2+) release nor Ca(2+) entry. However, under pretreatment of thapsigargin (ThG), BCR stimulation induced La(3+)-resistant Ca(2+) entry into both WT and IP(3)R-KO cells. These results indicate that BCR stimulation and Ca(2+) store depletion work in concert to activate the La(3+)-resistant Ca(2+) entry pathway. B-SOC was inhibited by tyrosine kinase inhibitor, genistein. In addition, B-SOC was completely abolished in Stim1-deficient cells and was restored by overexpression of yellow fluorescent protein (YFP)-tagged Stim1, but was unaffected by double knockdown of Orai1/Orai2. These results demonstrate a unique non-CCE pathway, in which Ca(2+) entry depends on Stim1 and tyrosine kinase activation. It is likely that similar regulation of Ca(2+) entry occurs in other cell types including salivary gland cells.
在大多数非兴奋性细胞中，细胞内钙库的耗竭会激活钙池调控的钙内流（CCE），这是一种对钙具有选择性且对镧（La(3+)）敏感的内流途径。在此，我们报告了一种对镧具有抗性的钙内流新机制，该机制由B细胞受体（BCR）刺激和钙库耗竭协同调控（B-SOC）。在野生型（WT）DT40细胞中，用抗IgM抗体刺激BCR会诱导钙释放，随后在存在0.3微摩尔镧（La(3+)）的情况下发生钙内流，而镧会完全阻断CCE。在肌醇1,4,5-三磷酸受体缺陷型（IP(3)R-KO）细胞中，BCR刺激既不引发钙释放也不引发钙内流。然而，在毒胡萝卜素（ThG）预处理下，BCR刺激会诱导镧抗性钙内流进入WT和IP(3)R-KO细胞。这些结果表明，BCR刺激和钙库耗竭共同作用以激活镧抗性钙内流途径。B-SOC受到酪氨酸激酶抑制剂染料木黄酮的抑制。此外，B-SOC在Stim1缺陷型细胞中完全被消除，并通过黄色荧光蛋白（YFP）标记的Stim1的过表达得以恢复，但不受Orai1/Orai2双敲低的影响。这些结果证明了一种独特的非CCE途径，其中钙内流依赖于Stim1和酪氨酸激酶激活。在包括唾液腺细胞在内的其他细胞类型中，可能也会发生类似的钙内流调控。
