An axon-intrinsic loop restricts nerve regeneration through axonal protein synthesis

Area of Science:

• Neuroscience
• Molecular Biology
• Regenerative Medicine

Background:

• Nerve injury triggers axonal synthesis of RNA Binding Protein KHSRP, which slows regeneration by promoting mRNA decay.
• Elevated KHSRP levels persist in axons post-injury, despite normalized calcium levels, suggesting a sustained regulatory mechanism.

Purpose of the Study:

• To investigate the regulatory loop involving REG3A and KHSRP in axon regeneration.
• To elucidate the role of localized mRNA translation in controlling axon growth dynamics.

Main Methods:

• Utilized techniques to measure axonal calcium (Ca ²⁺) levels and protein synthesis post-axotomy.
• Investigated the effects of Reg3a depletion on growth cone calcium oscillations and nerve regeneration.
• Analyzed the interplay between REG3A, KHSRP, and mRNA translation in regenerating axons.

Main Results:

• Axonal KHSRP levels are sustained by alternating translation of Reg3a and Khsrp.
• REG3A stimulates ER Ca ²⁺ release, activating PERK and increasing Khsrp translation.
• Reg3a depletion attenuated growth cone Ca ²⁺ oscillations, reduced KHSRP synthesis, and accelerated peripheral nerve regeneration.

Conclusions:

• The REG3A-KHSRP signaling pathway forms an intrinsic axonal loop that decelerates axon growth via localized mRNA translation.
• Targeting this loop offers a potential strategy for enhancing peripheral nerve regeneration.