STEROL INDEPENDENT REGULATION OF HMG-COA REDUCTASE

我们已经证明，一个建立的果蝇细胞系（Kc细胞）， 一个可行的实验模型，其中定义甾醇独立 HMG-CoA还原酶（HMGR）活性的调节。 Kc细胞调节HMGR 活性对甲羟戊酸可用性的响应。 此外，当前 有证据表明，对于HMGR抑制， 在异戊烯基焦磷酸（IPP）的远端。 我们观察到， HMGR抑制与总IPP通量、总中性 类异戊二烯脂质合成或水溶性类异戊二烯磷酸酯 profile. KC细胞似乎转移了至少50%的甲羟戊酸 碳转化为n-脂肪酸和TCA不溶性终产物。 由于我们不 结Kc细胞如何代谢C10/C15 prenols也没有潜在的作用 该途径的中间产物可能在甲羟戊酸的调节中起作用 综合，为这项建议制定了两个相关的目标：（1） 确定C10/C15异戊烯醇催化剂是否与甲羟戊酸介导的 HMG-CoA还原酶活性的调节和（2）概述Kc细胞C10/C15 异戊烯醇催化剂并定义该途径的选定酶。 为了直接证明HMG-CoA变化之间的因果关系， 还原酶的功能能力和假定的IPP后调节信号 分子，制定了另一个具体目标：（3）利用 功能性电穿孔Kc细胞模型，以识别、直接评估 假定的IPP后调节信号分子，并研究其模式 行动（S）。 我们的具体目标的实现，与Kc模式，应 提供了一个更清晰的了解固醇独立调节 真核细胞的甲羟戊酸代谢。 这些信息也将 提供了一个框架，在其中分析甲羟戊酸介导的调节， 更复杂的脊椎动物细胞中的类异戊二烯合成。

We have demonstrated that an established Drosophila cell line (Kc cells) is a viable experimental model in which to define sterol independent regulation of HMG-CoA reductase (HMGR) activity. Kc cells modulated HMGR activity in response to mevalonate availability. Furthermore, current evidence suggests that a regulatory signal molecule, for HMGR suppression, was distal to isopentenyll-pyrophosphate (IPP). We observed no simple correlation between HMGR suppression and total IPP flux, total neutral isoprenoid lipid synthesis, or water soluble isoprenoid phosphate ester profile. Kc cells appeared to divert minimally 50% of their mevalonate carbon to n-fatty acids and TCA insoluble end products. Since we do not knot how Kc cells metabolize C10/C15 prenols nor the potential role intermediates from this pathway might play in the regulation of mevalonate synthesis, two related aims were developed for this proposal: (1) to determine if C10/C15 prenol catabolism was linked to mevalonate mediated modulation of HMG-CoA reductase activity and (2) to outline Kc cell C10/C15 prenol catabolism and define selected enzymes of this pathway. In order to demonstrate directly causal linkages between changes in HMG-CoA reductase's functional capacity and the putative post IPP regulatory signal molecule, an additional specific aim was formulated: (3) to utilize a functional, electroporated Kc cell model to identify, directly evaluate putative post IPP regulatory signal molecules, and investigate their mode of action(s). Realization of our Specific Aims, with the Kc model, should provide a clearer understanding of sterol-independent regulation of mevalonate metabolism by eukaryotic cells. Such information will also provide a framework in which to analyze mevalonate mediated regulation of isoprenoid synthesis in the more complex vertebrate cell.