Signaling and cross-talk by C5a and UDP in macrophages selectively use PLCbeta3 to regulate intracellular free calcium.
نویسندگان
چکیده
Studies in fibroblasts, neurons, and platelets have demonstrated the integration of signals from different G protein-coupled receptors (GPCRs) in raising intracellular free Ca(2+). To study signal integration in macrophages, we screened RAW264.7 cells and bone marrow-derived macrophages (BMDM) for their Ca(2+) response to GPCR ligands. We found a synergistic response to complement component 5a (C5a) in combination with uridine 5'-diphosphate (UDP), platelet activating factor (PAF), or lysophosphatidic acid (LPA). The C5a response was Galpha(i)-dependent, whereas the UDP, PAF, and LPA responses were Galpha(q)-dependent. Synergy between C5a and UDP, mediated by the C5a and P2Y6 receptors, required dual receptor occupancy, and affected the initial release of Ca(2+) from intracellular stores as well as sustained Ca(2+) levels. C5a and UDP synergized in generating inositol 1,4,5-trisphosphate, suggesting synergy in activating phospholipase C (PLC) beta. Macrophages expressed transcripts for three PLCbeta isoforms (PLCbeta2, PLCbeta3, and PLCbeta4), but GPCR ligands selectively used these isoforms in Ca(2+) signaling. C5a predominantly used PLCbeta3, whereas UDP used PLCbeta3 but also PLCbeta4. Neither ligand required PLCbeta2. Synergy between C5a and UDP likewise depended primarily on PLCbeta3. Importantly, the Ca(2+) signaling deficiency observed in PLCbeta3-deficient BMDM was reversed by re-constitution with PLCbeta3. Neither phosphatidylinositol (PI) 3-kinase nor protein kinase C was required for synergy. In contrast to Ca(2+), PI 3-kinase activation by C5a was inhibited by UDP, as was macropinocytosis, which depends on PI 3-kinase. PLCbeta3 may thus provide a selective target for inhibiting Ca(2+) responses to mediators of inflammation, including C5a, UDP, PAF, and LPA.
منابع مشابه
Signaling and Cross-talk by C5a and UDP in Macrophages
Studies in fibroblasts, neurons, and platelets have demonstrated the integration of signals from different G proteincoupled receptors (GPCRs) in raising intracellular freeCa2 . To study signal integration in macrophages, we screened RAW264.7 cells and bone marrow-derived macrophages (BMDM) for their Ca2 response to GPCR ligands. We found a synergistic response to complement component 5a (C5a) i...
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ورودعنوان ژورنال:
- The Journal of biological chemistry
دوره 283 25 شماره
صفحات -
تاریخ انتشار 2008