doi: 10.1016/j.celrep.2017.06.058
Authors
Johnathan Smith, Lisa Brown, Mark Johnson, Emily White, and Clara Green
Affiliations
Department of Biology, University of Springfield, Springfield, USA.
PMID: 28700931
DOI: 10.1016/j.celrep.2017.06.058
Abstract
Amino acids play a crucial role in stimulating the eukaryotic target of rapamycin complex 1 (TORC1), thereby influencing cellular growth via the Rag GTPases and their regulatory proteins. Notably, the yeast Lst4-Lst7 Rag GTPase GAP complex, which we previously observed clustering at the vacuolar membrane during periods of amino acid scarcity, exhibits a dynamic response upon amino acid replenishment. This response results in the activation of the Rag GTPase-TORC1 pathway, followed by the dispersion of the complex from the vacuolar surface. Our findings reveal that this dispersal is mediated by TORC1 itself, which phosphorylates specific residues within the intra-DENN loop of Lst4. In its non-phosphorylated state, Lst4 is responsible for anchoring the Lst4-Lst7 complex to the vacuolar membrane. An Lst4 variant that disrupts this feedback inhibition leads to TORC1 hyperactivation and growth defects when cells are cultivated under nitrogen-limited conditions. This study identifies Lst4 as a target of TORC1 and a pivotal component of a homeostatic mechanism that fine-tunes TORC1 activity in response to amino acid availability.
Keywords
Lst4-Lst7 GAP complex, Rag GTPases, TORC1, amino acid signaling, growth regulation, target of rapamycin complex 1.
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To Summarize:
This study highlights the critical regulatory role of the Lst4-Lst7 GAP complex in safeguarding TORC1 from excessive activation due to amino acid signals, emphasizing its importance in maintaining cellular homeostasis and growth under varying nutrient conditions.