A novel Stim1-dependent, non-capacitative Ca2+ entry pathway is activated by B cell receptor stimulation and depletion of Ca2+ stores.
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.
Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan.
Takao
T
Morita
Akihiko
A
Tanimura
Yoshihiro
Y
Baba
Tomohiro
T
Kurosaki
Yosuke
Y
Tojyo
D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002645:Chickens; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008565:Membrane Proteins / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology
D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D019284:Thapsigargin; D011505:Protein-Tyrosine Kinases; D002118:Calcium