Biochemical and Biophysical Research Communications
Lysophosphatidic acid is a mediator of Trp-Lys-Tyr-Met-Val-d-Met-induced calcium influx
Section snippets
Materials and methods
Materials. Lysophosphatidic acid (1-myristyl-2-hydroxy-sn-glycero-3-phosphate, sodium salt), lysophosphatidylcholine (1-myristyl-2-hydroxy-sn-glycero-phosphocholine), lysophosphatidylethanolamine (1-myristyl-2-hydroxy-sn-glycero-phosphoethanolamine), and lysophosphatidylserine (1-myristyl-2-hydroxy-sn-glycero-phosphoserine) were from Avanti polar lipids (Alabaster, AL). Sphingosine-1-phosphate, phytosphingosine-1-phosphate, MAFP (methyl arachidonylfluorophosphonate), AACOCF3
LPA stimulates Ca2+ influx without Ca2+ release in U937 cells
In this study, we examined the effect of LPA on calcium influx in U937 cells. When U937 cells were stimulated with various concentrations of LPA in the absence of extracellular Ca2+, no significant change in the cytosolic Ca2+ concentration was observed (Fig. 1A). However, the addition of extracellular Ca2+ to LPA-stimulated U937 cells caused a dramatic Ca2+ influx (Fig. 1A). This LPA-induced Ca2+ influx increased according to the added Ca2+ concentration and showed maximal activity at around 1
Discussion
This study demonstrates that LPA plays a role in the regulation of Ca2+ influx in U937 cells. Moreover, the generation of LPA is crucially required for GPCR (FPRL1)-induced Ca2+ influx in U937 cells. Since many reports have demonstrated the activation of cell surface receptors, such as LPA1, LPA2, and LPA3 by LPA, we also checked whether U937 cells express cell surface LPA receptors by RT-PCR analysis. We found that U937 cells express the mRNA transcript of LPA2, but not those of LPA1 and LPA3
Acknowledgments
This work was supported by Grant 02-PJ1-PG10-20706-0001 from the Korea Health 21 R&D Project, Ministry of Health and Welfare, Republic of Korea (to Y.S.B.). We thank Dr. D.S. Im at Pusan National University College of Pharmacy for his helpful discussion.
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