Ong J M, Kirchgessner T G, Schotz M C, Kern P A
Division of Endocrinology, Cedars-Sinai Medical Center, Los Angeles, California 90048.
J Biol Chem. 1988 Sep 15;263(26):12933-8.
Lipoprotein lipase (LPL) is the enzyme responsible for hydrolysis of circulating triglyceride-rich lipoproteins and is important for storage of adipocyte lipid. To study the regulation of LPL synthetic rate in adipose tissue, primary cultures of isolated rat adipocytes were pulse-labeled with [35S]methionine, and LPL was immunoprecipitated with an LPL-specific antibody. A pulse-chase experiment identified the cellular and secreted forms of LPL as a 55-57-kDa protein. In the presence of heparin, there was a large increase in secretion of newly synthesized LPL from the cells, although heparin did not stimulate cellular LPL synthetic rate. When cells were exposed to insulin for 2 h, pulse-labeling revealed that insulin stimulated a maximal dose-related increase in LPL synthetic rate of 300% of control. This increase in LPL synthetic rate was observed after an exposure to insulin for as little as 60 min and was accompanied by only a 10-25% increase in total protein synthesis. In addition, insulin had no effect on the turnover of intracellular LPL. Using a cDNA probe for LPL, insulin induced a 2-fold increase in the LPL mRNA. Thus, insulin stimulated an increase in specific LPL mRNA in isolated rat adipocytes. This increase in LPL mRNA then leads to an increase in the synthetic rate of the LPL protein.
脂蛋白脂肪酶（LPL）是负责水解循环中富含甘油三酯的脂蛋白的酶，对脂肪细胞脂质的储存很重要。为了研究脂肪组织中LPL合成速率的调节，用[35S]甲硫氨酸对分离的大鼠脂肪细胞原代培养物进行脉冲标记，并用LPL特异性抗体免疫沉淀LPL。脉冲追踪实验确定LPL的细胞形式和分泌形式为一种55 - 57 kDa的蛋白质。在肝素存在的情况下，细胞中新合成的LPL分泌大幅增加，尽管肝素不刺激细胞LPL合成速率。当细胞暴露于胰岛素2小时时，脉冲标记显示胰岛素刺激LPL合成速率最大剂量相关增加，达到对照的300%。在暴露于胰岛素仅60分钟后就观察到LPL合成速率的这种增加，并且总蛋白质合成仅增加10 - 25%。此外，胰岛素对细胞内LPL的周转没有影响。使用LPL的cDNA探针，胰岛素使LPL mRNA增加了2倍。因此，胰岛素刺激分离的大鼠脂肪细胞中特异性LPL mRNA增加。LPL mRNA的这种增加随后导致LPL蛋白合成速率增加。
