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Cytokine secretion requires phosphatidylcholine synthesis
Correspondence to Suzanne Jackowski: suzanne.jackowski{at}stjude.org
Choline cytidylyltransferase (CCT) is the rate-limiting enzyme in the phosphatidylcholine biosynthetic pathway. Here, we demonstrate that CCT
-mediated phosphatidylcholine synthesis is required to maintain normal Golgi structure and function as well as cytokine secretion from the Golgi complex. CCT
is localized to the trans-Golgi region and its expression is increased in lipopolysaccharide (LPS)-stimulated wild-type macrophages. Although LPS triggers transient reorganization of Golgi morphology in wild-type macrophages, similar structural alterations persist in CCT
-deficient cells. Pro–tumor necrosis factor
and interleukin-6 remain lodged in the secretory compartment of CCT
-deficient macrophages after LPS stimulation. However, the lysosomal-mediated secretion pathways for interleukin-1β secretion and constitutive apolipoprotein E secretion are unaltered. Exogenous lysophosphatidylcholine restores LPS-stimulated secretion from CCT
-deficient cells, and elevated diacylglycerol levels alone do not impede secretion of pro–tumor necrosis factor
or interleukin-6. These results identify CCT
as a key component in membrane biogenesis during LPS-stimulated cytokine secretion from the Golgi complex.
L. Wang's present address is Department of Internal Medicine, University of California, Davis, Davis, CA 95616.
Abbreviations used in this paper: ApoE, apolipoprotein E; CCT, cytidylyltransferase; CDP–Cho, cytidine diphosphocholine; C/EPT, choline/ethanolamine phosphotransferase; CPT, choline phosphotransferase; ERGIC-53, ER–Golgi intermediate compartment 53-kD protein; edelfosine, Et-18-OCH3; fMLP, formyl-methionylleucylphenylalanine; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IL-1β, interleukin-1β; IL-6, interleukin-6; LCM, L cell–conditioned medium; LPS, lipopolysaccharide; lysoPC, lysophosphatidylcholine; PEMT, phosphatidylethanolamine methyltransferase; PGE2, prostaglandin E2; PLD1, phospholipase D1; pro-TNF
, precursor form of TNF
; PtdCho, phosphatidylcholine; PtdEtn, phosphatidylethanolamine; PtdOH, phosphatidic acid; P'tse, phosphatase; qRT-PCR, quantitative RT-PCR; SM, sphingomyelin; TAPI, N-(D,L-[2-(hydroxyaminocarbonyl)methyl]-4-methylpentanoyl)-L-3-(2'naphthyl)-alanyl-L-alanine, 2-aminoethylamide; TACE, TNF
-converting enzyme. © 2008 Tian et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jcb.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).
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