Fyn phosphorylates AMPK to inhibit AMPK activity and AMP-dependent activation of autophagy

Area of Science:

• Cellular Biology
• Molecular Medicine
• Metabolic Research

Background:

• Proto-oncogene Fyn is implicated in decreased energy expenditure and altered metabolic phenotypes.
• Fyn negatively regulates muscle mass through inhibition of LKB1 and activation of STAT3, impacting autophagy.
• AMP-activated protein kinase (AMPK), a downstream target of LKB1, is crucial for controlling autophagy.

Purpose of the Study:

• To investigate the direct mechanism by which Fyn affects AMPK activity.
• To elucidate the role of Fyn in mediating the effects of pro-inflammatory cytokines on autophagy.
• To determine if Fyn-dependent inhibition of AMPK is responsible for TNFα-induced autophagy suppression.

Main Methods:

• Investigated Fyn's effect on AMPK enzymatic activity and complex assembly.
• Utilized pro-inflammatory cytokine Tumor Necrosis Factor alpha (TNFα) treatment in cellular models.
• Employed site-directed mutagenesis of AMPKα at Y436 to assess functional impact.
• Measured Fyn activity, AMPKα phosphorylation, and AICAR-dependent AMPK activation.

Main Results:

• Fyn directly phosphorylates AMPKα on Y436, inhibiting its enzymatic activity without affecting complex assembly.
• TNFα treatment increased Fyn activity, leading to Fyn-dependent AMPKα phosphorylation and reduced AMPK activation.
• Mutation of AMPKα at Y436 abolished TNFα-induced autophagy inhibition.
• Fyn acts as a key mediator of TNFα signaling, impacting autophagy and apoptosis through AMPK inhibition.

Conclusions:

• Fyn directly inhibits AMPK activity via phosphorylation at Y436.
• Fyn plays a critical role in the signaling pathway by which TNFα suppresses autophagy.
• Targeting the Fyn-AMPK interaction may offer therapeutic strategies for metabolic and inflammatory conditions affecting muscle mass.