Control of leucine-dependent mTORC1 pathway through chemical intervention of leucyl-tRNA synthetase and RagD interaction

Abstract

Leucyl-tRNA synthetase (LRS) is known to function as leucine sensor in the mammalian target of rapamycin complex 1 (mTORC1) pathway. However, the pathophysiological significance of its activity is not well understood. Here, we demonstrate that the leucine sensor function for mTORC1 activation of LRS can be decoupled from its catalytic activity. We identified compounds that inhibit the leucine-dependent mTORC1 pathway by specifically inhibiting the GTPase activating function of LRS, while not affecting the catalytic activity. For further analysis, we selected one compound, BC-LI-0186, which binds to the RagD interacting site of LRS, thereby inhibiting lysosomal localization of LRS and mTORC1 activity. It also effectively suppressed the activity of cancer-associated MTOR mutants and the growth of rapamycin-resistant cancer cells. These findings suggest new strategies for controlling tumor growth that avoid the resistance to existing mTOR inhibitors resulting from cancer-associated MTOR mutations.

PHD1 controls muscle mTORC1 in a hydroxylation-independent manner by stabilizing leucyl tRNA synthetase

“…In fact, the leucine sensing ability of LRS in muscle is not described. To confirm that LRS is required for leucine mediated mTORC1 activation in myotubes, we inhibited the interaction of LRS with RagD by using BC-LI-0186 52 and confirmed reduced leucine mediated activation of mTORC1 ( Supplementary Fig. 4i).…”

“…LRS belongs to a family of proteins known as aminoacyl tRNA synthetases whose canonical function is to ensure that the genetic code is accurately deciphered by attaching the correct amino acid to the equivalent tRNA 20 . However, LRS also serves as a leucine sensor for mTORC1 by functioning as a GTP activating protein for RagD 52 , thereby promoting lysosomal translocation of mTORC1. GTP-bound RagD subsequently promotes the LRSdependent leucylation of RagA at K 142 (K Leu 142) upon leucine stimulation 21 .…”

Coordination of the leucine-sensing Rag GTPase cycle by leucyl-tRNA synthetase in the mTORC1 signaling pathway

“…4E). Since LRS functions as a RagD-GAP (13), we investigated how LRS knockdown or BC-LI-0186, which is a specific inhibitor for LRS-RagD binding (15) Fig. 2.…”

Nontranslational function of leucyl-tRNA synthetase regulates myogenic differentiation and skeletal muscle regeneration

“…We identified the IRS1-PI3K-Akt pathway as a mediator of LRS inhibition of myoblast differentiation in vitro (Figure 3, D and E, and Supplemental Figure 3D). To investigate whether Akt mediates LRS function in vivo, we administered BC-LI-0186 together with an Akt inhibitor, triciribine, for 14 days after BaCl 2 and inhibit leucine-dependent activation of mTORC1 in cells with high specificity, without affecting the aminoacylation activity of LRS (22). We reasoned that this inhibitor could specifically target the nontranslational function of LRS and recapitulate the effect of LRS knock down in myogenesis.…”