Functional Interactions between Mldp (LSDP5) and Abhd5 in the Control of Intracellular Lipid Accumulation
Functional Interactions between Mldp (LSDP5) and Abhd5 in the Control of Intracellular Lipid Accumulation
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DOI：
10.1074/jbc.m808251200
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发表时间：
2009-01-30
影响因子：
4.8
通讯作者：
Zhu, Zhengxian
中科院分区：
文献类型：
--
作者：
Granneman, James G.;Moore, Hsiao-Ping H.;Zhu, Zhengxian
细胞内脂滴表面附近的蛋白质-蛋白质相互作用部分地调节细胞脂质代谢。这项工作研究了Abhd5，脂肪酶Atgl的蛋白激活剂，和Mldp，在氧化组织中高度表达的脂滴支架蛋白之间的功能相互作用。Abhd5是高度针对个别脂滴含有Mldp在显微切割的心肌纤维。Mldp在转染的成纤维细胞中结合Abhd5，并将其定向至与Mldp浓度成比例的脂滴。原位蛋白质-蛋白质相互作用的分析表明，Abhd5和Mldp的相互作用主要发生在脂滴的表面上，如果不是排他的话。油酸处理迅速增加Abhd5和Mldp之间的相互作用，这种作用被抑制甘油三酯合成的药理学抑制。Abhd5-Mldp相互作用的功能作用使用与Mldp的结合大大降低的小鼠Abhd5（E262K）的突变体来探索。Mldp促进Atgl与野生型的亚细胞共定位和相互作用，但不促进突变体Abhd5。这种差异相互作用反映在Atgl活性的细胞测定中。在不存在Mldp的情况下，野生型和突变体Abhd5在减少脂滴形成方面同样有效。相比之下，突变体Abhd5不能防止表达Mldp的细胞中的脂滴积累，尽管Atgl相当大地靶向含有Mldp的脂滴。这些结果表明Abhd5和Mldp之间的相互作用是动态的，并且对于调节Atgl在含有Mldp的脂滴中的活性是必需的。
Cellular lipid metabolism is regulated in part by protein-protein interactions near the surface of intracellular lipid droplets. This work investigated functional interactions between Abhd5, a protein activator of the lipase Atgl, and Mldp, a lipid droplet scaffold protein that is highly expressed in oxidative tissues. Abhd5 was highly targeted to individual lipid droplets containing Mldp in microdissected cardiac muscle fibers. Mldp bound Abhd5 in transfected fibroblasts and directed it to lipid droplets in proportion to Mldp concentration. Analysis of protein-protein interactions in situ demonstrated that the interaction of Abhd5 and Mldp occurs mainly, if not exclusively, on the surface of lipid droplets. Oleic acid treatment rapidly increased the interaction between Abhd5 and Mldp, and this effect was suppressed by pharmacological inhibition of triglyceride synthesis. The functional role of the Abhd5-Mldp interaction was explored using a mutant of mouse Abhd5 (E262K) that has greatly reduced binding to Mldp. Mldp promoted the subcellular colocalization and interaction of Atgl with wild type, but not mutant, Abhd5. This differential interaction was reflected in cellular assays of Atgl activity. In the absence of Mldp, wild type and mutant Abhd5 were equally effective in reducing lipid droplet formation. In contrast, mutant Abhd5 was unable to prevent lipid droplet accumulation in cells expressing Mldp despite considerable targeting of Atgl to lipid droplets containing Mldp. These results indicate that the interaction between Abhd5 and Mldp is dynamic and essential for regulating the activity of Atgl at lipid droplets containing Mldp.