Ca2+ signaling induced by sphingosine 1-phosphate and lysophosphatidic acid in mouse B cells

Abstract

Lysophospholipids (LPLs) such as lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are chemotactic for lymphocytes, and increases of in cytosolic [Ca(2+)] signal the regulation of lymphocyte activation and migration. Here, the authors investigated the effects of LPA and S1P on [Ca(2+)](c) in mouse B cell lines (WEHI-231 and Bal-17) and primary B cells isolated from mouse spleen and bone marrow, and focused on the modulation of store-operated Ca(2+) entry (SOCE) by LPLs. In Bal-17 (a mature B cell line) both LPA and S1P induced a transient [Ca(2+)](c) increase via a phospholipase C pathway. In addition, pretreatment with LPLs was found to augment thapsigargin-induced SOCE in Bal-17 cells. However, in WEHI-231 (an immature B cell line) LPLs had no significant effect on [Ca(2+)](c) or SOCE. Furthermore, in freshly isolated splenic B cells (SBCs) and bone marrow B cells (BMBCs), LPLs induced only a small increase in [Ca(2+)](c). Interestingly, however, pretreatment with LPLs markedly increased SOCE in primary B cells, and this augmentation was more prominent in BMBCs than SBCs. The unidirectional influx of Ca(2+) was measured using Ba(2+) as a surrogate ion. Similarly, Ba(2+) influx was also found to be markedly increased by LPLs in SBCs and BMBCs. Summarizing, LPLs were found to strongly augment SOCE-mediated Ca(2+)-signaling in mouse B cells. However, unlike the mature Bal-17 cell line, PLC-dependent Ca(2+) release was insignificant in primary B cells and inWEHI-231.