Rab Geranylgeranylation: a Novel Therapeutic Target in Multiple Myeloma

描述（由申请人提供）：多发性骨髓瘤（MM）的特征是分泌大量单克隆蛋白（MP）的恶性浆细胞增殖。到目前为止，还没有开发出靶向MP分泌的治疗策略。小GTP酶的Rab家族在细胞内囊泡运输中起关键作用。损害Rab蛋白的香叶基香叶基化的试剂通过破坏MP分泌诱导MM细胞凋亡，导致MP在细胞内积聚和未折叠蛋白反应途径（UPR）的激活。有效的抑制剂的香叶基香叶基转移酶II（GGT酶II），酶负责后修饰Rab蛋白，尚未开发。此外，人们对个体Rab在管理MP贩运方面的作用知之甚少， 选择性破坏MM细胞中Rab功能的效果。因此，提出了以下目标：1）开发新的GGT酶II抑制剂和2）探索Rabs在调节MM细胞中MP运输中的作用。新型GGT酶II抑制剂的开发将涉及计算机辅助药物设计、化学合成和生物学表征。试剂将被设计和合成为含有三个部分：将与焦磷酸盐识别位点相互作用的不可水解的极性头部基团，将与催化锌位点相互作用的锌结合基序，以及将与末端异戊二烯位点相互作用的类异戊二烯或类异戊二烯样链。点击化学方法的使用将允许 多个新药剂家族的产生。将使用基于荧光的酶测定来确定化合物的抑制活性。其他研究将涉及确定酶特异性，评估选择性抑制MM细胞中Rab香叶基香叶基化的能力，评价细胞毒性作用，并检查对MP运输的影响。为了探索单个Rab在MM细胞中的作用，将确定siRNA介导的所选Rab同种型沉默对关键细胞过程（包括MP运输、UPR和细胞凋亡）的影响。这项工作将导致更好地了解Rabs在MM细胞中的作用，并开发治疗MM患者的新型药物。

DESCRIPTION (provided by applicant): Multiple myeloma (MM) is characterized by the proliferation of malignant plasma cells which secrete large quantities of monoclonal protein (MP). As yet, no therapeutic strategies have been developed which target MP secretion. The Rab family of small GTPases plays key roles in intracellular vesicle trafficking. Agents which impair the geranylgeranylation of Rab proteins induce apoptosis of MM cells by disrupting MP secretion, resulting in accumulation of MP within the cells and activation of the unfolded protein response pathway (UPR). Potent inhibitors of geranylgeranyltransferase II (GGTase II), the enzyme responsible for post-translationally modifying Rab proteins, have yet to be developed. In addition, little is known regarding the role of individual Rabs in regulating MP trafficking and the effects of selectively disrupting Rab function in MM cells. The following aims are therefore proposed: 1) To develop novel inhibitors of GGTase II and 2) To explore the role of Rabs in regulating MP trafficking in MM cells. The development of novel inhibitors of GGTase II will involve computer-assisted drug design, chemical synthesis, and biological characterization. Agents will be designed and synthesized to contain three moieties: a non-hydrolysable polar head group which will interact with the pyrophosphate recognition site, a zinc-binding motif which will interact with the catalytic zinc site, and an isoprenoid or isoprenoid-like chain which will interact with the terminal isoprene site. The use of a click-chemistry approach will allow for the generation of multiple families of novel agents. A fluorescence-based enzyme assay will be used to determine the inhibitory activity of the compounds. Additional studies will involve determining enzyme specificity, assessing the ability to selectively inhibit Rab geranylgeranylation in MM cells, evaluating the cytotoxic effects, and examining the effects on MP trafficking. To explore the role of individual Rabs in MM cells, the effects of siRNA-mediated silencing of selected Rab isoforms on key cellular processes, including MP trafficking, the UPR, and apoptosis, will be determined. This work will lead to a better understanding of the role of Rabs in MM cells and to the development of novel agents with which to treat patients with MM.