Determining AMPK Activation via the Lysosomal v-ATPase-Ragulator-AXIN/LKB1 Axis.

Recent studies have revealed how AMPK is activated inside the cell and animal tissues: in response to low glucose, AXIN tethers LKB1, by virtue of their constitutive association, to AMPK located on the surface of late endosome/lysosome. Importantly, the lysosomal v-ATPase (vacuolar ATPase)-Ragulator complex, when primed by glucose starvation or concanamycin A, facilitates AXIN/LKB1 to interact with AMPK. Here, we describe the experimental procedures of the assays for detecting the translocation of AXIN/LKB1 or the assembly of the AXIN-based AMPK-activating complexes on the late endosome/lysosome. The methods in this chapter will be useful for determining whether various metabolic stresses or pharmacological stimuli activate AMPK via the v-ATPase-Ragulator-AXIN/LKB1 axis, which also concomitantly inactivates mTORC1. Detailed protocols for determining the levels of adenylates are also described.