N-myristoyltransferase deficiency impairs AMPK activation and promotes synovial tissue inflammation

N-myristoyltransferase (NMT) attaches the fatty acid myristate to the N-terminal glycine of proteins to sort them into soluble and membrane-bound fractions. Function of the energy-sensing AMP-activated protein kinase (AMPK) is myristoylation-dependent. In rheumatoid arthritis (RA), pathogenic T cells shift glucose away from ATP production towards synthetic and proliferative programs, promoting proliferation, cytokine production, and tissue invasion. We found that RA T cells have a defect in NMT1 function, which prevented AMPK activation and enabled unopposed mTORC1 signaling. Lack of the myristate lipid tail disrupted the lysosomal translocation and activation of AMPK. Instead, myristoylation-incompetent RA T cells hyperactivated the mTORC1 pathway and differentiated into pro-inflammatory T(H)1 and T(H)17 T helper cells. In vivo, NMT1 loss caused robust synovial tissue inflammation, whereas forced NMT1 overexpression rescued AMPK activation and suppressed synovitis. Thus, NMT1 has tissue-protective functions by facilitating lysosomal recruitment of AMPK and dampening of mTORC1 signaling.