Center for Molecular Medicine, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, the Netherlands; Oncode Institute, Utrecht, the Netherlands.
Center for Molecular Medicine, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, the Netherlands.
Mol Cell. 2024 Nov 21;84(22):4368-4384.e6. doi: 10.1016/j.molcel.2024.10.009. Epub 2024 Oct 31.
To stimulate cell growth, the protein kinase complex mTORC1 requires intracellular amino acids for activation. Amino-acid sufficiency is relayed to mTORC1 by Rag GTPases on lysosomes, where growth factor signaling enhances mTORC1 activity via the GTPase Rheb. In the absence of amino acids, GATOR1 inactivates the Rags, resulting in lysosomal detachment and inactivation of mTORC1. We demonstrate that in human cells, the release of mTORC1 from lysosomes depends on its kinase activity. In accordance with a negative feedback mechanism, activated mTOR mutants display low lysosome occupancy, causing hypo-phosphorylation and nuclear localization of the lysosomal substrate TFE3. Surprisingly, mTORC1 activated by Rheb does not increase the cytoplasmic/lysosomal ratio of mTORC1, indicating the existence of mTORC1 pools with distinct substrate specificity. Dysregulation of either pool results in aberrant TFE3 activity and may explain nuclear accumulation of TFE3 in epileptogenic malformations in focal cortical dysplasia type II (FCD II) and tuberous sclerosis (TSC).
为了刺激细胞生长，蛋白激酶复合物 mTORC1 需要细胞内的氨基酸才能被激活。氨基酸的充足程度通过溶酶体上的 Rag GTPases 传递给 mTORC1，在溶酶体中，生长因子信号通过 GTPase Rheb 增强 mTORC1 的活性。在没有氨基酸的情况下，GATOR1 使 Rag 失活，导致溶酶体脱离并使 mTORC1 失活。我们证明，在人类细胞中，mTORC1 从溶酶体中的释放依赖于其激酶活性。根据负反馈机制，激活的 mTOR 突变体显示出低的溶酶体占有率，导致溶酶体底物 TFE3 的低磷酸化和核定位。令人惊讶的是，由 Rheb 激活的 mTORC1 不会增加 mTORC1 的细胞质/溶酶体比值，这表明存在具有不同底物特异性的 mTORC1 池。任何一个池的失调都会导致 TFE3 活性异常，这可能解释了在局灶性皮质发育不良 II 型 (FCD II) 和结节性硬化症 (TSC) 中的致痫性畸形中 TFE3 的核积累。
