KAT7-mediated CANX (calnexin) crotonylation regulates leucine-stimulated MTORC1 activity

Amino acids play crucial roles in the MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) pathway. However, the underlying mechanisms are not fully understood. Here, we establish a cell-free system to mimic the activation of MTORC1, by which we identify CANX (calnexin) as an essential regulator for leucine-stimulated MTORC1 pathway. CANX translocates to lysosomes after leucine deprivation, and its loss of function renders either the MTORC1 activity or the lysosomal translocation of MTOR insensitive to leucine deprivation. We further find that CANX binds to LAMP2 (lysosomal associated membrane protein 2), and LAMP2 is required for leucine deprivation-induced CANX interaction with the Ragulator to inhibit Ragulator activity toward RRAG GTPases. Moreover, leucine deprivation promotes the lysine (K) 525 crotonylation of CANX, which is another essential condition for the lysosomal translocation of CANX. Finally, we find that KAT7 (lysine acetyltransferase 7) mediates the K525 crotonylation of CANX. Loss of KAT7 renders the MTORC1 insensitivity to leucine deprivation. Our findings provide new insights for the regulatory mechanism of the leucine-stimulated MTORC1 pathway.

Automated summary

In this study, a cell-free system was established to mimic the activation of MTORC1, and CANX was identified as an essential regulator for leucine-stimulated MTORC1 pathway. CANX was found to translocate to lysosomes after leucine deprivation, and its interaction with LAMP2 was required to inhibit Ragulator activity toward RRAG GTPases. Moreover, the crotonylation of CANX at lysine (K) 525 was promoted by leucine deprivation, and KAT7 was identified as the enzyme responsible for this modification. These findings provide new insights into the regulatory mechanism of the leucine-stimulated MTORC1 pathway.