Increases in Retrograde Injury Signaling Complex-Related Transcripts in Central Axons following Injury

Abstract

Axons in the peripheral nervous system respond to injury by activating retrograde injury signaling (RIS) pathways, which promote local axonal protein synthesis (LPS) and neuronal regeneration. RIS is also initiated following injury of neurons in the central nervous system (CNS). However, regulation of the localization of axonal mRNA required for LPS is not well understood. We used a hippocampal explant system to probe the regulation of axonal levels of RIS-associated transcripts following axonal injury. Axonal levels of importin β1 and RanBP1 were elevated biphasically at 1 and 24 hrs after axotomy. Transcript levels for β-actin, a prototypic axonally synthesized protein, were similarly elevated. Our data suggest differential regulation of axonal transcripts. At 1 hr after injury, deployment of actinomycin revealed that RanBP1, but not importin β1, requires de novo mRNA synthesis. At 24 hrs after injury, use of importazole revealed that the second wave of increased axonal mRNA levels required importin β-mediated nuclear import. We also observed increased importin β1 axonal protein levels at 1 and 6 hrs after injury. RanBP1 levels and vimentin levels fluctuated but were unchanged at 3 and 6 hrs after injury. This study revealed temporally complex regulation of axonal transcript levels, and it has implications for understanding neuronal response to injury in the CNS.

Targeting eIF2α in TBI-induced traumatic optic neuropathy: Effects of Salubrinal and the Integrated Stress Response Inhibitor.

“…While optic nerve crush, transection, and ocular blast injures optic nerve axons in or behind the eye, we injure the optic nerve in a replicable 1-1.5 mm section just proximal to the optic chiasm. (Hetzer et al, 2023) Thus, most of what we know about the proximal axon is from in vitro or ex vivo studies (Almasieh et al, 2017; Hao et al, 2016; Hao et al, 2019; Baleriola et al, 2014; Mok et al, 2009; Pathak et al, 2016). This distinction is made more important because differences between signaling in distal and proximal axon segments have been unearthed including retrograde phosphatidyl serine externalization (Almasieh et al, 2017), upregulation of the DLK-cJUN pathway (Asghari Adib et al, 2018; Kievit, 2019; Ugbode et al, 2019; Larhammar et al, 2017), local calcium signaling (Frati et al, 2017; Calixto et al, 2012), and more.…”

“…While optic nerve crush, transection, and ocular blast injures optic nerve axons in or behind the eye, we injure the optic nerve in a replicable 1-1.5 mm section just proximal to the optic chiasm. (Hetzer et al, 2023) Thus, most of what we know about the proximal axon is from in vitro or ex vivo studies (Almasieh et al, 2017;Hao et al, 2016;Hao et al, 2019;Baleriola et al, 2014;Mok et al, 2009;Pathak et al, 2016). This distinction is made more important because differences between signaling in distal (which was not certified by peer review) is the author/funder.…”