Research Article
Sphingosylphosphorylcholine induces proliferation of human adipose tissue-derived mesenchymal stem cells via activation of JNK

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Sphingosylphosphorylcholine (SPC) has been implicated in a variety of cellular responses, including proliferation and differentiation. In this study, we demonstrate that d-erythro-SPC, but not l-threo-SPC, stereoselectively stimulated the proliferation of human adipose tissue-derived mesenchymal stem cells (hADSCs), with a maximal increase at 5 μM, and increased the intracellular concentration of Ca2+ ([Ca2+]i) in hADSCs, which do not express known SPC receptors (i.e., OGR1, GPR4, G2A, and GPR12). The SPC-induced proliferation and increase in [Ca2+]i were sensitive to pertussis toxin (PTX) and the phospholipase C (PLC) inhibitor U73122, suggesting that PTX-sensitive G proteins, Gi or Go, and PLC are involved in SPC-induced proliferation. In addition, SPC treatment induced the phosphorylation of c-Jun and extracellular signal-regulated kinase, and SPC-induced proliferation was completely prevented by pretreatment with the c-Jun N-terminal kinase (JNK)-specific inhibitor SP600125 but not with the MEK-specific inhibitor U0126. Furthermore, the SPC-induced proliferation and JNK activation were completely attenuated by overexpression of a dominant negative mutant of JNK2, and the SPC-induced activation of JNK was inhibited by pretreatment with PTX or U73122. Treatment of hADSCs with lysophosphatidic acid (LPA) receptor antagonist, Ki16425, had no impact on the SPC-induced increase in [Ca2+]i. However, SPC-induced proliferation was partially, but significantly, attenuated by pretreatment of the cells with Ki16425.These results indicate that SPC stimulates the proliferation of hADSCs through the Gi/Go-PLC-JNK pathway and that LPA receptors may be responsible in part for the SPC-induced proliferation.

c-Jun N-terminal kinase
phospholipase C
G proteins

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Abbreviations:

    BAPTA

    1,2-bis(o-aminophenoxy)ethane-N,N,N,N-tetraacetic acid

    [Ca2+]i

    intracellular concentration of Ca2+

    DN-JNK2

    dominant negative mutant of JNK2

    DN-MEK1

    dominant negative mutant of MEK1

    ERK

    extracellular signal-regulated kinase

    GFP

    green fluorescent protein

    GPCR

    G protein-coupled receptor

    GST

    glutathione-S-transferase

    HA

    hemagglutinin

    hADSC

    human adipose tissue-derived mesenchymal stem cell

    JNK

    c-Jun N-terminal kinase

    LPA

    lysophosphatidic acid

    LPC

    lysophosphatidylcholine

    MAP

    mitogen-activated protein

    MTT

    3-(4,5-dimethyl-2-thiozol)-2,5-diphenyl-2H-tetrazolium bromide

    PTX

    pertussis toxin

    S1P

    sphingosine-1-phosphate

    SPC

    sphingosylphosphorylcholine

Published, JLR Papers in Press, December 7, 2005.