AKT is a serine/threonine kinase that plays an important role in metabolism, cell growth, and cytoskeletal dynamics. AKT is activated by two kinases, PDK1 and mTORC2. Although the regulation of PDK1 is well understood, the mechanism that controls mTORC2 is unknown. Here, by investigating insulin receptor signaling in human cells and biochemical reconstitution, we found that insulin induces the activation of mTORC2 toward AKT by assembling a supercomplex with KRAS4B and RHOA GTPases, termed KARATE (KRAS4B-RHOA-mTORC2 Ensemble). Insulin-induced KARATE assembly is controlled via phosphorylation of GTP-bound KRAS4B at S181 and GDP-bound RHOA at S188 by protein kinase A. By developing a KARATE inhibitor, we demonstrate that KRAS4B-RHOA interaction drives KARATE formation. In adipocytes, KARATE controls insulin-dependent translocation of the glucose transporter GLUT4 to the plasma membrane for glucose uptake. Thus, our work reveals a fundamental mechanism that activates mTORC2 toward AKT in insulin-regulated glucose homeostasis.

AKT 是一种丝氨酸/苏氨酸激酶，在新陈代谢、细胞生长和细胞骨架动力学中起重要作用。AKT 由两种激酶 PDK1 和 mTORC2 激活。虽然 PDK1 的调控已广为人知，但控制 mTORC2 的机制尚不清楚。在这里，通过研究人体细胞中的胰岛素受体信号传导和生化重建，我们发现胰岛素通过与 KRAS4B 和 RHOA GTPase 组装一个称为 KARATE (KRAS4B-RHOA-mTORC2 Ensemble) 的超复合物来诱导 mTORC2 向 AKT 激活。胰岛素诱导的空手道组装是通过蛋白激酶 A 在 S181 磷酸化 GTP 结合的 KRAS4B 和在 S188 的 GDP 结合 RHOA 来控制的。通过开发空手道抑制剂，我们证明 KRAS4B-RHOA 相互作用驱动空手道的形成。在脂肪细胞中，空手道控制葡萄糖转运蛋白 GLUT4 向质膜的胰岛素依赖性易位，以吸收葡萄糖。因此，我们的工作揭示了在胰岛素调节的葡萄糖稳态中激活 mTORC2 朝向 AKT 的基本机制。