Abstract
Purpose :
Highly polarized and compartmentalized neurons respond rapidly and precisely to surrounding stimuli at long distances. This capacity has been linked in part to specific RNA localization and local translation. 3’ untranslated regions (3’UTRs) regulate RNA localization. In this study, we explored RNA translation and dependence on 3’UTRs in axonal growth cones of hippocampal neurons expressing axonal targeting 3’UTR, dendrite targeting 3’UTR and no 3’UTR in vitro, to explore mechanisms involved in regional growth cone translation.
Methods :
We generated constructs carrying photoswitchable fluorescent reporter Dendramyr with axonal targeting GAP43-3’UTR, dendrite targeting Nrgn-3’UTR, and no 3’UTR. Dendra signals in growth cones were recorded in primary hippocampal neuron cultures before and after photoswitching to observe local translation-dependent recovery of Dendra signal, with and without protein synthesis inhibitors. Growth cone protein synthesis was also studied in response to treatment with brain-derived neurotrophic factor (BDNF), forskolin, and KCl-induced depolarization and repolarization.
Results :
Neurons expressing axonal targeting Dendramyr 3’GAP43 showed recovery of Dendra signal in distal growth cones 40 minutes after photoswitching; treatment with anisomycin disrupted recovery, demonstrating that recovery was due to local new protein synthesis. No significant recovery was observed in neurons with the expression of Dendramyr 3’Nrgn or Dendramyr controls. Axon-targeted Dendra translation increased with 2 hours treatment with BDNF and was even greater with combination treatment with BDNF and forskolin. KCl-induced depolarization for 2 hours increased local translation, whereas 20 hours of KCl decreased of local Dendra signal after photoswitching. The disruption of local Dendra translation in growth cones after 20 hours incubation with KCl was restored after washing out KCl.
Conclusions :
BDNF/TrkB activation increases local translation of axon-targeted mRNA in distal growth cones; cellular repolorization restores long-term depolarization induced disruption of local protein synthesis of reporter Dendra in distal growth cones. Live cell recording distal growth cones in primary neurons expressing axon-targeting Dendramyr 3’GAP43 is a promising platform for screening of candidates that support local translation and promote axon growth.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.