McIntosh Avery L, Storey Stephen M, Atshaves Barbara P
Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station, TX 77843, USA.
Lipids. 2010 Jun;45(6):465-77. doi: 10.1007/s11745-010-3424-1. Epub 2010 May 15.
During the last several years, intracellular lipid droplets have become the focus of intense study. No longer an inert bystander, the lipid droplet is now known as a dynamic organelle contributing lipids to many cellular events. However, while the dynamics of cholesterol efflux from both the plasma membrane and lipid droplets have been studied, less is known regarding the efflux of sphingomyelin from these membranes. In order to address this issue, sphingomyelin efflux kinetics and binding affinities from different intracellular pools were examined. When compared to the plasma membrane, lipid droplets had a smaller exchangeable sphingomyelin efflux pool and the time required to efflux that pool was significantly shorter. Fluorescence binding assays revealed that proteins in the plasma membrane and lipid droplet pool bound sphingomyelin with high affinity. Further characterization identified adipose differentiation-related protein (ADRP) as one of the sphingomyelin binding proteins in the lipid droplet fraction and revealed that ADRP demonstrated saturable binding to 6-((N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-hexanoyl)sphingosyl-phosphocholine (NBD-sphingomyelin) and also 2-(6-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl-1-hexadecanoyl-sn-glycero-3-phosphocholine (NBD-phosphatidylcholine) with binding affinities in the nanomolar range. Taken together, these results suggest that lipid droplet associated proteins such as ADRP may play a significant role in regulating the intracellular distribution of phospholipids and lipids in general. Overall, insights from the present work suggest new and important roles for lipid droplets and ADRP in phospholipid metabolism.
在过去几年中，细胞内脂滴已成为深入研究的焦点。脂滴不再是一个惰性旁观者，现在已知它是一种动态细胞器，为许多细胞活动贡献脂质。然而，虽然已经研究了胆固醇从质膜和脂滴的流出动力学，但对于鞘磷脂从这些膜中的流出了解较少。为了解决这个问题，研究了不同细胞内池的鞘磷脂流出动力学和结合亲和力。与质膜相比，脂滴具有较小的可交换鞘磷脂流出池，且流出该池所需的时间明显更短。荧光结合测定表明，质膜和脂滴池中的蛋白质与鞘磷脂具有高亲和力结合。进一步的表征确定脂肪分化相关蛋白（ADRP）是脂滴部分中的鞘磷脂结合蛋白之一，并表明ADRP对6-((N-(7-硝基苯并-2-恶唑-1,3-二氮杂环丁烷-4-基)氨基)-己酰基)鞘氨醇-磷酸胆碱（NBD-鞘磷脂）以及2-(6-(7-硝基苯并-2-恶唑-1,3-二氮杂环丁烷-4-基)氨基)己酰基-1-十六烷酰基-sn-甘油-3-磷酸胆碱（NBD-磷脂酰胆碱）表现出饱和结合，结合亲和力在纳摩尔范围内。综上所述，这些结果表明，诸如ADRP之类的脂滴相关蛋白可能在调节磷脂和脂质的细胞内分布中发挥重要作用。总体而言，本研究的见解表明脂滴和ADRP在磷脂代谢中具有新的重要作用。
