Intracellular bacteria such as Salmonella enterica serovar Typhimurium (ST) drastically alter metabolism upon entry into host cells such as macrophages. During ST infection, AMPK activity is elevated, although the underlying mechanisms and resulting signaling consequences are poorly characterized. Xenophagy, or the autophagic degradation of pathogens, requires a coordinated, localization-dependent response to effectively kill bacteria. While AMPK has been implicated in xenophagy induction, how AMPK signaling affects host defense against intracellular pathogens remains unclear.
Myristoylation of the AMPK β subunits regulates both AMPK activity and subcellular localization. However, how AMPK myristoylation status influences infection dynamics is not well understood. To investigate this, we used bone marrow macrophages derived from mice with Gly-2-Ala (G2A) knock-in mutations at the myristoylation sites on both the β1 and β2 subunits.
Preliminary experiments using purified TLR agonists indicate that G2A macrophages produce lower levels of proinflammatory cytokine genes such as Il6 and Il1b following stimulation with the bacterial products lipopolysaccharide and Pam3CSK4, suggesting that AMPK myristoylation status may affect the host response to bacteria. When macrophages were infected with virulent ST, we observed a similar suppression of cytokine production in G2A cells relative to wild type. Next steps include characterizing the role of AMPK myristoylation in ST-infected cells using flow cytometry and microscopy, as well as investigating the importance of AMPK myristoylation during in vivo infection.
Collectively, this work expands our understanding of AMPK in innate immunity and provides insight into how metabolism affects the acute response to infection both in vitro and in vivo.