MTP regulated by an alternate promoter is essential for NKT cell development.
MTP regulated by an alternate promoter is essential for NKT cell development.
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由替代启动子调节的MTP对于NKT细胞发育至关重要。
DOI：
10.1084/jem.20062006
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发表时间：
2007-03-19
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微粒体甘油三酯转移蛋白（MTP）是一种对载脂蛋白B（apo B）分泌至关重要的内质网脂质转移蛋白，调节CD 1d抗原呈递。我们通过聚合酶链反应和北方分析，在非apoB分泌组织（包括胸腺细胞和抗原呈递细胞（APC））中鉴定了MTP变体1（MTPv 1），这是小鼠MTP的一种新型剪接变体。从转染细胞中分离的MTPv 1的Edman降解揭示了三个独特的残基;然而，重组MTP和MTPv 1具有等同的蛋白质二硫键异构酶关联、亚细胞定位、甘油三酯转移、磷脂转移、对抑制剂的响应以及支持apoB分泌的能力。MTP和MTPv 1在体外有效地将磷脂酰乙醇胺转移到CD 1d。在用MTP拮抗剂处理的胎儿胸腺器官培养物（FTOC）中，NKT细胞不能发育。MTP抑制的FTOC产生的CD 1d四聚体阳性细胞数量可忽略不计，并且在用抗CD 3或α-半乳糖神经酰胺脉冲的APC刺激后，IL-4产生明显缺陷。CD 4 + CD 8 + FTOC细胞上的CD 1d表达不受MTP抑制的影响。因此，我们的研究结果表明，MTPV 1在胸腺细胞是至关重要的NKT细胞的发展。我们假设，当MTP不活动时，CD 1d运输到细胞表面，并且不呈现脂质或不能介导NKT细胞选择和/或对溶酶体编辑难治的脂质。
Microsomal triglyceride transfer protein (MTP), an endoplasmic reticulum lipid transfer protein critical for apolipoprotein B (apoB) secretion, regulates CD1d antigen presentation. We identified MTP variant 1 (MTPv1), a novel splice variant of mouse MTP, by polymerase chain reaction and Northern analysis in non–apoB-secreting tissues, including thymocytes and antigen-presenting cells (APCs). Edman degradation of MTPv1 isolated from transfected cells revealed three unique residues; however, recombinant MTP and MTPv1 had an equivalent protein disulfide isomerase association, subcellular localization, triglyceride transfer, phospholipid transfer, response to inhibitors, and ability to support apoB secretion. MTP and MTPv1 efficiently transferred phosphatidylethanolamine to CD1d in vitro. NKT cells fail to develop in fetal thymic organ culture (FTOC) treated with MTP antagonists. MTP-inhibited FTOCs produced negligible numbers of CD1d tetramer–positive cells and exhibited marked defects in IL-4 production upon stimulation with anti-CD3 or α-galactosylceramide–pulsed APCs. CD1d expression on CD4+CD8+ FTOC cells was unaffected by MTP inhibition. Thus, our results demonstrate that MTPv1 in thymocytes is critical to NKT cell development. We hypothesize that, when MTP is inactive, CD1d traffics to the cell surface and presents no lipid or a lipid that is incapable of mediating NKT cell selection and/or is refractory to lysosomal editing.