AK4 expression coordinates dual AMPK and mTOR signaling - PROJECT SUMMARY
Two opposing signaling pathways which are critical regulators of cell growth and metabolism are the AMPK and
mTOR pathways. mTOR generally promotes cellular growth and proliferation, while AMPK inhibits mTOR and
generally suppresses growth and proliferation. Both pathways are acutely responsive to cellular nutrient and
energy levels and demands. An adenylate kinase (AK4) has been identified whose expression regulates cellular
adenosine levels and concurrent activation of AMPK and mTOR, resulting in both enhanced proliferation and
activation of responses such as autophagy in multiple cell types. These findings position AK4 upstream of both
signaling pathways, with AK4 expression able to coordinate activation of both pathways. Each of these pathways
are important for maintaining cellular homeostasis, and dysregulated mTOR and AMPK signaling are implicated
in numerous human diseases. The objectives of this proposal are to characterize the mechanism by which AK4
regulates adenosine nucleotide pools, concurrent AMPK and mTOR signaling, and the downstream biological
effects of AK4 expression-mediated mTOR and AMPK activation. The aims of this proposal are 1) to identify the
mechanistic basis whereby AK4 exerts its biological effects; 2) to identify the mechanism whereby AK4 regulates
concomitant AMPK and mTOR activation; 3) to define the functional consequences of AK4-mediated activation
of mTOR- and AMPK-dependent biological actions on cell biology. To achieve these goals, AK4 expression
levels will be genetically enhanced or suppressed, and relevant mechanisms which may modulate ATP levels
and mTOR and AMPK signaling will be assessed. These include measuring glycolytic and OXPHOS flux,
adenosine nucleotide biosynthesis, subcellular localization of activated AMPK and mTOR, and effector protein
status. Finally, the biological effects (protein synthesis, proliferation, autophagy, mitochondrial biogenesis, etc.)
of these cellular events will be characterized for their potential to contribute to cellular homeostasis. Together,
these goals and approaches will define the mechanistic basis by which AK4 regulates AMPK and mTOR
signaling.
