Role of Leu and Val synthesis in sensing mitochondrial nutrient and energy availability.

In yeast, limiting Leu and Val import forces branched-chain amino acid synthesis to mirror mitochondrial anabolic capacity, which then reshapes translation and transcriptional programs.

• Why it matters: Cells must integrate nutrient availability with mitochondrial activity to coordinate metabolism and growth, but the sensing mechanisms linking these processes are not well understood.
• What they did: Yeast was engineered to rely on Leu/Val synthesis under import limitation; reduced Val synthesis activated Gcn2, while reduced Leu synthesis inhibited TORC1, lowering translation efficiency and growth.
• The result: This program reduced Mig1 levels, suppressed the Warburg/Crabtree effect, and promoted alternative carbon use; pharmacological Leu/Val synthesis inhibition induced similar reprogramming even in nutrient-rich medium.