Differential transport and local translation of cytoskeletal, injury-response, and neurodegeneration protein mRNAs in axons.
Recent studies have begun to focus on the signals that regulate axonal protein synthesis and the functional significance of localized protein synthesis. However, identification of proteins that are synthesized in mammalian axons has been mainly based on predictions. Here, we used axons purified from cultures of injury-conditioned adult dorsal root ganglion (DRG) neurons and proteomics methodology to identify axonally synthesized proteins. Reverse transcription (RT)-PCR from axonal preparations was used to confirm that the mRNA for each identified protein extended into the DRG axons. Proteins and the encoding mRNAs for the cytoskeletal proteins beta-actin, peripherin, vimentin, gamma-tropomyosin 3, and cofilin 1 were present in the axonal preparations. In addition to the cytoskeletal elements, several heat shock proteins (HSP27, HSP60, HSP70, grp75, alphaB crystallin), resident endoplasmic reticulum (ER) proteins (calreticulin, grp78/BiP, ERp29), proteins associated with neurodegenerative diseases (ubiquitin C-terminal hydrolase L1, rat ortholog of human DJ-1/Park7, gamma-synuclein, superoxide dismutase 1), anti-oxidant proteins (peroxiredoxins 1 and 6), and metabolic proteins (e.g., phosphoglycerate kinase 1 (PGK 1), alpha enolase, aldolase C/Zebrin II) were included among the axonally synthesized proteins. Detection of the mRNAs encoding each of the axonally synthesized proteins identified by mass spectrometry in the axonal compartment indicates that the DRG axons have the potential to synthesize a complex population of proteins. Local treatment of the DRG axons with NGF or BDNF increased levels of cytoskeletal mRNAs into the axonal compartment by twofold to fivefold but had no effect on levels of the other axonal mRNAs studied. Neurotrophins selectively increased transport of beta-actin, peripherin, and vimentin mRNAs from the cell body into the axons rather than changing transcription or mRNA survival in the axonal compartment.
Willis
Dianna
D
Nemours Biomedical Research, Alfred I. DuPont Hospital for Children, Wilmington, Delaware 19803, USA.
Li
Ka Wan
KW
Zheng
Jun-Qi
JQ
Chang
Jay H
JH
Smit
August B
AB
Smit
August
A
Kelly
Theresa
T
Merianda
Tanuja T
TT
Sylvester
James
J
van Minnen
Jan
J
Twiss
Jeffery L
JL
D000818:Animals; D001369:Axons / Q000378:metabolism*; D019208:Brain-Derived Neurotrophic Factor / Q000502:physiology; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000096:biosynthesis / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D020932:Nerve Growth Factor / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics*; D019636:Neurodegenerative Diseases / Q000378:metabolism; D009475:Neurons, Afferent / Q000378:metabolism; D014176:Protein Biosynthesis; D034443:RNA Transport; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000293:injuries
D019208:Brain-Derived Neurotrophic Factor; D003598:Cytoskeletal Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D020932:Nerve Growth Factor