標題: Missense Mutation in APOC3 within the C-terminal Lipid Binding Domain of Human ApoC-III Results in Impaired Assembly and Secretion of Triacylglycerol-rich Very Low Density Lipoproteins EVIDENCE THAT ApoC-III PLAYS A MAJOR ROLE IN THE FORMATION OF LIPID PRECURSORS WITHIN THE MICROSOMAL LUMEN
作者: Qin, Wen
Sundaram, Meenakshi
Wang, Yuwei
Zhou, Hu
Zhong, Shumei
Chang, Chia-Ching
Manhas, Sanjay
Yao, Erik F.
Parks, Robin J.
McFie, Pamela J.
Stone, Scot J.
Jiang, Zhenghui G.
Wang, Congrong
Figeys, Daniel
Jia, Weiping
Yao, Zemin
生物科技學系
Department of Biological Science and Technology
公開日期: 5-八月-2011
摘要: Hepatic assembly of triacylglycerol (TAG)-rich very low density lipoproteins (VLDL) is achieved through recruitment of bulk TAG (presumably in the form of lipid droplets within the microsomal lumen) into VLDL precursor containing apolipoprotein (apo) B-100. We determined protein/lipid components of lumenal lipid droplets (LLD) in cells expressing recombinant human apoC-III (C3wt) or a mutant form (K58E, C3KE) initially identified in humans that displayed hypotriglyceridemia. Although expression of C3wt markedly stimulated secretion of TAGand apoB-100 as VLDL(1), the K58E mutation (located at the C-terminal lipid binding domain) abolished the effect in transfected McA-RH7777 cells and in apoc3-null mice. Metabolic labeling studies revealed that accumulation of TAG in LLD was decreased (by 50%) in cells expressing C3KE. A Fat Western lipid protein overlay assay showed drastically reduced lipid binding of the mutant protein. Substituting Lys(58) with Arg demonstrated that the positive charge at position 58 is crucial for apoC-III binding to lipid and for promoting TAG secretion. On the other hand, substituting both Lys(58) and Lys(60) with Glu resulted in almost entire elimination of lipid binding and loss of function in promoting TAG secretion. Thus, the lipid binding domain of apoC-III plays a key role in the formation of LLD for hepatic VLDL assembly and secretion.
URI: http://dx.doi.org/10.1074/jbc.M110.203679
http://hdl.handle.net/11536/20440
ISSN: 0021-9258
DOI: 10.1074/jbc.M110.203679
期刊: JOURNAL OF BIOLOGICAL CHEMISTRY
Volume: 286
Issue: 31
起始頁: 27769
結束頁: 27780
顯示於類別:期刊論文


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