Preprint Article Version 1 This version is not peer-reviewed

Chromatolysis: Do Injured Axons Regenerate Poorly when Ribonucleases Fragment or Degranulate Rough Endoplasmic Reticulum, Disaggregate Polyribosomes, Degrade Monoribosomes and Lyse RNA?

Version 1 : Received: 16 February 2018 / Approved: 16 February 2018 / Online: 16 February 2018 (16:19:57 CET)

How to cite: Moon, L. Chromatolysis: Do Injured Axons Regenerate Poorly when Ribonucleases Fragment or Degranulate Rough Endoplasmic Reticulum, Disaggregate Polyribosomes, Degrade Monoribosomes and Lyse RNA?. Preprints 2018, 2018020111 (doi: 10.20944/preprints201802.0111.v1). Moon, L. Chromatolysis: Do Injured Axons Regenerate Poorly when Ribonucleases Fragment or Degranulate Rough Endoplasmic Reticulum, Disaggregate Polyribosomes, Degrade Monoribosomes and Lyse RNA?. Preprints 2018, 2018020111 (doi: 10.20944/preprints201802.0111.v1).

Abstract

After axonal injury, chromatolysis (fragmentation of Nissl substance) occurs in both intrinsic neurons (whose processes are within the CNS) and extrinsic neurons (whose axons extend outside the CNS). Electron microscopy shows that chromatolysis involves fission of the rough endoplasmic reticulum. In intrinsic neurons (which do not regenerate axons) or in extrinsic neurons denied axon regeneration, chromatolysis is often accompanied by degranulation (loss of ribosomes from rough endoplasmic reticulum), disaggregation of polyribosomes and degradation of monoribosomes into dust-like particles. Ribosomes and rough endoplasmic reticulum may also be degraded in autophagic vacuoles by Ribophagy and Reticulophagy, respectively. In other words, chromatolysis is disruption of parts of the protein synthesis infrastructure. Whereas some neurons may show transient or no chromatolysis, severely injured neurons can remain chromatolytic and never again synthesise normal levels of protein; some may atrophy or die. What molecule(s) cause fragmentation or degranulation of rough endoplasmic reticulum, disaggregation of polyribosomes and degradation of monoribosomes? Ribonucleases can modify (and perhaps fragment) rough endoplasmic reticulum; various endoribonucleases can degrade mRNA causing polyribosomes to unchain and disperse; they can disassemble monoribosomes; Ribonuclease 5 can control rRNA synthesis and degrade tRNA; Ribonuclease T2 can degrade ribosomes, rough endoplasmic reticulum and RNA within autophagic vacuoles; and Ribonuclease IRE1α acts as a stress sensor within the endoplasmic reticulum. Regeneration might be improved after axonal injury by protecting the protein synthesis machinery from catabolism; targeting ribonucleases could be a profitable strategy.

Subject Areas

chromatolysis, ribonuclease, angiogenin, endoplasmic reticulum, ribosome

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