Heterotrimeric G-proteins are signaling switches broadly divided into four families based on the sequence and functional similarity of their Gα subunits: Gs, Gi/o, Gq/11, and G12/13. Artificial mutations that activate Gα subunits of each of these families have long been known to induce oncogenic transformation in experimental systems. With the advent of next-generation sequencing, activating hotspot mutations in Gs, Gi/o, or Gq/11 proteins have also been identified in patient tumor samples. In contrast, patient tumor-associated G12/13 mutations characterized to date lead to inactivation rather than activation. By using bioinformatic pathway analysis and signaling assays, here we identified cancer-associated hotspot mutations in Arg-200 of Gα13 (encoded by GNA13) as potent activators of oncogenic signaling. First, we found that components of a G12/13-dependent signaling cascade that culminates in activation of the Hippo pathway effectors YAP and TAZ is frequently altered in bladder cancer. Up-regulation of this signaling cascade correlates with increased YAP/TAZ activation transcriptional signatures in this cancer type. Among the G12/13 pathway alterations were mutations in Arg-200 of Gα13, which we validated to promote YAP/TAZ-dependent (TEAD) and MRTF-A/B-dependent (SRE.L) transcriptional activity. We further showed that this mechanism relies on the same RhoGEF-RhoGTPase cascade components that are up-regulated in bladder cancers. Moreover, Gα13 Arg-200 mutants induced oncogenic transformation in vitro as determined by focus formation assays. In summary, our findings on Gα13 mutants establish that naturally occurring hotspot mutations in Gα subunits of any of the four families of heterotrimeric G-proteins are putative cancer drivers.

中文翻译：

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Gα13 中自然发生的热点癌症突变促进致癌信号传导


异三聚体 G 蛋白是信号传导开关，根据其 Gα 亚基的序列和功能相似性，大致分为四个家族：Gs、Gi/o、Gq/11 和 G12/13。人们早就知道，激活每个家族的 Gα 亚基的人工突变会在实验系统中诱导致癌转化。随着新一代测序的出现，在患者肿瘤样本中也发现了 Gs、Gi/o 或 Gq/11 蛋白的激活热点突变。相比之下，迄今为止，患者肿瘤相关的 G12/13 突变导致失活而不是激活。通过使用生物信息学通路分析和信号传导测定，我们在 Gα13（由 GNA13 编码）的 Arg-200 中鉴定出与癌症相关的热点突变，作为致癌信号传导的有效激活剂。首先，我们发现，最终导致 Hippo 通路效应子 YAP 和 TAZ 激活的 G12/13 依赖性信号级联的组成部分在膀胱癌中经常发生改变。在这种癌症类型中，这种信号级联的上调与 YAP/TAZ 激活转录特征的增加相关。 G12/13 通路改变包括 Gα13 的 Arg-200 突变，我们验证了该突变可促进 YAP/TAZ 依赖性 (TEAD) 和 MRTF-A/B 依赖性 (SRE.L) 转录活性。我们进一步表明，这种机制依赖于在膀胱癌中上调的相同 RhoGEF-RhoGTPase 级联成分。此外，通过病灶形成试验确定，Gα13 Arg-200 突变体在体外诱导致癌转化。总之，我们对 Gα13 突变体的研究结果表明，异源三聚体 G 蛋白四个家族中任何一个的 Gα 亚基中自然发生的热点突变都是假定的癌症驱动因素。