Structure, mechanism, and pharmacology of BRAF and its partners in the RAS/RAF/MAP kinase pathway

摘要 RAS/MAP激酶通路在多种人类癌症中被异常激活。V600E BRAF是该途径中的一种激酶，BRAF突变导致大约一半的黑色素瘤，并且是黑色素瘤的驱动因素。 还有很多其他癌症。尽管几十年的强烈兴趣和调查，BRAF监管并不好- 明白此外，针对RAS/MAPK途径的化合物表现出人们对其知之甚少 药理作用。BRAF抑制剂，如维罗非尼，有效地抑制V600 E BRAF，但它们 矛盾地激活野生型BRAF。MEK（BRAF下游的一种激酶）的抑制剂在其功效上不同 这取决于该途径是否被KRAS相对于BRAF的突变激活。统称 这些药物的混乱药理学反映了我们对调节和生物化学的不完整知识， 这一途径的运作，并限制了我们的能力，开发针对BRAF和RAS/MAPK的靶向治疗 通路 在过去的二十年里，我的实验室一直专注于蛋白激酶的结构生物学， 他们在癌症中的失调，以及癌症药物的发现。我们已经应用了我们基本的生物物理，生物化学， 和野生型和突变型EGFR的结构见解，以发现新的药理学药物类别 靶向突变受体，包括突变体选择性共价和变构抑制剂， 克服阻力机制。我们现在采用类似的结构和机械方法， 揭开BRAF调节和药理学的神秘面纱。我们的目标是了解BRAF在结构上的调节， 详细，破译BRAF和MEK抑制剂的复杂药理学，并开发新的药物， 以多核苷酸选择性的方式靶向该途径。为了实现这些目标，我们将确定 使用冷冻电子显微镜观察自抑制和活性BRAF复合物。我们将重建 使用纯化的组分将KRAS转化为ERK，以便剖析BRAF和MEK活化的机制，并探测 靶向该途径的药物的作用。此外，我们还将把这些重组措施结合起来使用 利用我们的结构洞察力，以多选择性方式发现靶向该途径的新药物。这些 研究将提供对BRAF调节的基本新理解，从长远来看，它们应该产生 更有效和耐受性更好的癌症治疗方法，由该途径的诱变激活驱动。

Abstract The RAS/MAP kinase pathway is aberrantly activated in a wide variety of human cancers. The V600E mutation in BRAF, a kinase in this pathway, causes approximately one-half of all melanomas and is the driver in many other cancers as well. Despite decades of intense interest and investigation, BRAF regulation is not well- understood. Furthermore, compounds targeting the RAS/MAPK pathway exhibit poorly understood pharmacologic effects. BRAF inhibitors, such as vemurafenib, potently inhibit V600E BRAF, but they paradoxically activate wild type BRAF. Inhibitors of MEK, a kinase downstream of BRAF, differ in their efficacy depending upon whether the pathway is activated by mutations in KRAS versus BRAF. Collectively, the confusing pharmacology of these agents reflects our incomplete knowledge of the regulation and biochemical workings of this pathway and limits our ability to develop targeted therapies for BRAF and the RAS/MAPK pathway. Over the last two decades, my laboratory has focused on the structural biology of protein kinases and their dysregulation in cancer, and on cancer drug discovery. We have applied our basic biophysical, biochemical and structural insights into wild-type and mutant EGFR to discover new classes of pharmacologic agents targeting the mutant receptor, including both mutant-selective covalent and allosteric inhibitors that can overcome resistance mechanisms. We are now applying an analogous structural and mechanistic approach to demystify BRAF regulation and pharmacology. Our objectives are to understand BRAF regulation in structural detail, to decipher the complex pharmacology of the BRAF and MEK inhibitors, and to develop new agents that target the pathway in a mutant-selective manner. To achieve these goals, we will determine the structure of autoinhibited and active BRAF complexes using cryo-electron microscopy. We will reconstitute the pathway from KRAS to ERK using purified components in order to dissect mechanisms of BRAF and MEK activation and probe the effects of pharmacologic agents that target the pathway. In addition, we will use these reconstitutions together with our structural insights to discover new agents that target the pathway in a mutant-selective manner. These studies will provide fundamental new understanding of BRAF regulation and, in the long term, they should yield more effective and better tolerated therapies for cancers driven by mutagenic activation of this pathway.