Surette M E, Chilton F H
Section on Pulmonary and Critical Care Medicine, Bowman Gray School of Medicine, Medical Center Boulevard, Winston-Salem, NC27157-1054, USA.
Biochem J. 1998 Mar 1;330 ( Pt 2)(Pt 2):915-21. doi: 10.1042/bj3300915.
The cell nucleus has been identified as a location to which several arachidonic acid-metabolizing enzymes are located in stimulated cells. However, little information exists describing the distribution of arachidonate-containing phospholipids associated with the nucleus or the control of their composition. In this study, nuclei isolated from human monocyte-like THP-1 cells were found to have a distribution of arachidonyl-phospholipids which is markedly different from that of other cellular membranes. THP-1 nuclei which contained 22% of total cellular arachidonate, showed a near equal distribution of arachidonate in 1-acyl-2-arachidonoyl-glycero-3-phosphocholine, 1-acyl-2-arachidonyl-glycero-3-phosphoethanolamine, 1-acyl-2-arachidonoyl-glycero-3-phosphoinositol and 1-alk-1-enyl-2-arachidonoyl-glycero-3-phosphoethanolamine molecular species. In contrast in non-nuclear membranes, arachidonate was located primarily in 1-alk-1-enyl-2-arachidonoyl-glycero-3-phosphoethanolamine molecular species which accounted for approximately half of the arachidonate in all non-nuclear phospholipids. Isolated nuclei were incapable of initially acylating arachidonic acid into their phospholipids in the absence of cellular cytosol. However, they were capable of efficiently remodelling existing arachidonate between phospholipid classes and subclasses. Isolated nuclei contained 25-30% of the cellular activity of CoA-independent transacylase, the key enzyme responsible for arachidonate-phospholipid remodelling. This enzyme is also critical in the control of arachidonate availability following cell stimulation. Given that the cellular distribution of arachidonate is such that nuclei are enriched in donor substrates for the CoA-independent transacylase reaction, that non-nuclear membranes are enriched in acceptor substrates and that nuclei have the enzymatic machinery to remodel arachidonate efficiently, these results suggest that CoA-independent transacylase may be responsible for the remodelling of arachidonate not only between different phospholipid species within the same organelles but also between different sub-cellular compartments.
细胞核已被确定为在受刺激细胞中几种花生四烯酸代谢酶所在的位置。然而，关于与细胞核相关的含花生四烯酸磷脂的分布及其组成控制的信息却很少。在本研究中，发现从人单核细胞样THP-1细胞中分离出的细胞核具有的花生四烯酰磷脂分布与其他细胞膜的分布明显不同。含有细胞总花生四烯酸22%的THP-1细胞核，在1-酰基-2-花生四烯酰甘油-3-磷酸胆碱、1-酰基-2-花生四烯酰甘油-3-磷酸乙醇胺、1-酰基-2-花生四烯酰甘油-3-磷酸肌醇和1-烷基-1-烯基-2-花生四烯酰甘油-3-磷酸乙醇胺分子种类中显示出花生四烯酸近乎相等的分布。相比之下，在非核膜中，花生四烯酸主要位于1-烷基-1-烯基-2-花生四烯酰甘油-3-磷酸乙醇胺分子种类中，其占所有非核磷脂中花生四烯酸的约一半。在没有细胞胞质溶胶的情况下，分离出的细胞核最初无法将花生四烯酸酰化到其磷脂中。然而，它们能够有效地在磷脂类别和亚类之间重塑现有的花生四烯酸。分离出的细胞核含有细胞中25 - 30%的不依赖辅酶A的转酰基酶活性，该酶是负责花生四烯酸-磷脂重塑的关键酶。这种酶在细胞刺激后花生四烯酸可用性的控制中也至关重要。鉴于花生四烯酸的细胞分布使得细胞核富含不依赖辅酶A的转酰基酶反应的供体底物，非核膜富含受体底物，并且细胞核具有有效重塑花生四烯酸的酶机制，这些结果表明不依赖辅酶A的转酰基酶可能不仅负责在同一细胞器内不同磷脂种类之间，而且负责在不同亚细胞区室之间重塑花生四烯酸。
