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Different signaling pathway between sphingosine‐1‐phosphate and lysophosphatidic acid in Xenopus oocytes: Functional coupling of the sphingosine‐1‐phosphate receptor to PLC‐xβ in Xenopus oocytes
Author(s) -
Noh SeungJae,
Kim MyungJun,
Shim Sangwoo,
Han JinKwan
Publication year - 1998
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199808)176:2<412::aid-jcp20>3.0.co;2-3
Subject(s) - lysophosphatidic acid , thapsigargin , phospholipase c , xenopus , sphingosine , endoplasmic reticulum , inositol trisphosphate receptor , sphingosine 1 phosphate , biology , microbiology and biotechnology , intracellular , inositol , receptor , gq alpha subunit , signal transduction , pertussis toxin , extracellular , g protein , biochemistry , gene
In Xenopus oocytes, both sphingosine‐1‐phosphate (S1P) and lysophosphatidic acid (LPA) activate Ca 2+ ‐dependent oscillatory Cl − currents by acting through membrane‐bound receptors. External application of 50 μM S1P elicited a long‐lasting oscillatory current that continued over 30 min from the beginning of oscillation, with 300 nA (n = 11) as a usual maximum peak of current, whereas 1‐μM LPA treatment showed only transiently oscillating but more vigorous current responses, with 2,800 nA (n = 18) as a maximum peak amplitude. Both phospholipid‐induced Ca 2+ ‐dependent Cl − currents were observed in the absence of extracellular Ca 2+ , were blocked by intracellular injection of the Ca 2+ chelator, EGTA, and could not be elicited by treatment with thapsigargin, an inhibitor of endoplasmic reticulum (ER) Ca 2+ ATPase. Intracellular Ca 2+ release appeared to be from inositol 1,4,5‐trisphosphate (IP 3 )‐sensitive Ca 2+ store, because Cl − currents were blocked by heparin injection. Pretreatment with the aminosteroid, U‐73122, an inhibitor of G protein‐mediated phospholipase C (PLC) activation, to oocytes inhibited the current responses evoked both by S1P and LPA. However, when they were injected with 10 ng of antisense oligonucleotide (AS‐ODN) against Xenopus phospholipase C (PLC‐xβ), oocytes could not respond to S1P application, whereas they responded normally to LPA, indicating that the S1P signaling pathway goes through PLC‐xβ, whereas LPA signaling goes through another unknown PLC. To determine the types of G proteins involved, we introduced AS‐ODNs against four types of G‐protein α subunits that were identified in Xenopus laevis; G q α, G 11 α, G 0 α, and G i1 α. Among AS‐ODNs against the Gαs tested, AS‐G q α and AS‐G i1 α to S1P and AS‐G q α and AS‐G 11 α to LPA specifically reduced current responses, respectively, to about 20–30% of controls. These results demonstrate that LPA and S1P, although they have similar structural features, release intracellular Ca 2+ from the IP 3 ‐sensitive pool, use different components in their signal transduction pathways in Xenopus oocytes. J. Cell. Physiol. 176:412–423, 1998. © 1998 Wiley‐Liss, Inc.