Abstract

In adulthood, the regenerative capacity of the injured brain circuit is poor, thereby preventing functional restoration. Rehabilitative physical exercise is a promising approach for enhancing the behavioral recovery after neuronal injury to both the central and peripheral nervous systems. The metabolic energy sensor AMPK acts as a mediator for the exercise benefit in Caenorhabditis elegans axon regeneration. However, the mechanistic understanding of upstream and downstream components of AMPK signaling in the physical exercise-mediated enhancement of axon regeneration is still unclear. Here, we addressed this question by combining swimming exercise with laser axotomy of C. elegans posterior lateral microtubule (PLM) neurons. Using a genetically encoded ATP sensor iATPsnFR1.0, we observed that immediately after swimming exercise, ATP level is decreased both in neuron and muscle. Further, we found that AICAR-mediated AMPK activation is sufficient to promote axon regeneration and functional recovery. The PAR-4/Liver kinase B1 acts upstream of AMPK to improve functional recovery through swimming exercise. We also found that the transcriptional regulators DAF-16 and MDT-15 mediate the beneficial effects of swimming by acting downstream of AMPK. MDT-15 functions within neuron to mediate the benefit of AMPK activation, whereas DAF-16 acts both in neuron and muscle to promote functional restoration. Additionally, we demonstrated that swimming exercise induces nuclear localization of DAF-16 in an AMPK-dependent manner. Our results showed that neuronal and non-neuronal arms of AMPK signaling play an integrative role in response to physical exercise to promote functional recovery after axon injury.