Xuelang Mu

This study identifies SPAR, a microprotein, as an inhibitor of SLC38A9, a lysosomal amino acid transporter, revealing its role in mTORC1 pathway regulation by blocking arginine transport and Rag GTPase recruitment.

This study shows that SLC38A9, a lysosomal amino acid transporter, has pH-dependent arginine uptake regulated by the histidine residue His544, which influences transport through protonation/deprotonation rather than direct substrate binding.