Expression of growth-associated protein B-50 (GAP43) in dorsal root ganglia and sciatic nerve during regenerative sprouting.
Recently it has been shown that B-50 is identical to the neuron-specific, growth-associated protein GAP43. The present study reports on the fate of B-50/GAP43 mRNA and B-50/GAP43 protein, determined by radioimmunoassay, in a rat model of peripheral nerve regeneration (sciatic nerve crush) over a period of 37 and 312 d, respectively. Moreover, the effects of repeated subcutaneous injection of the neurotrophic peptide Org.2766 (an ACTH4-9 analog) and of a conditioning lesion on B-50/GAP43 protein levels in the regenerating nerve and dorsal root ganglia (DRG) were investigated. Both treatments enhanced the functional recovery as evidenced by a foot-flick withdrawal test. Immunocytochemical analysis using antineurofilament antibodies revealed a peptide-induced increase in the number of outgrowing sprouts in the sciatic nerve. Both the peptide and the conditioning lesion amplified the crush lesion-induced increase in B-50 protein content in the nerve as determined by radioimmunoassay. B-50 protein levels seem to correlate proportionally with the number of sprouts. In the DRG of the crushed sciatic nerve, the time course of B-50 expression was studied. B-50 mRNA was quantified from Northern blots. A linear increase up to 10 times the basal level of B-50 mRNA was observed 2 d postsurgery, followed by a gradual decline to normal levels at day 37. The first significant rise in B-50 mRNA level became apparent between 8 and 16 hr after placement of the crush lesion. The first significant rise in B-50 protein level occurred 40 hr after the crush lesion, reaching a plateau of 3 times the basal level between day 6 and 20. B-50 protein levels in DRG cell bodies remained elevated up to 60 d after crush, a period much longer than that observed for B-50 mRNA. Thus, during a later phase of peripheral axonal regeneration, the presence of B-50 appears to be prolonged, probably by an increase in half-life and not so much by enhanced transcription. Treatment with Org.2766 did not affect the B-50/GAP43 levels in DRG cell bodies during the first 6 d following crush. Conditioning lesion resulted in a DRG B-50/GAP43 protein amount at the same level as in rats 14 d after the test lesion. B-50/GAP43 levels in DRG are probably influenced by the rapid axonal transport of the protein, as has been reported by others.
Van der Zee
C E
CE
Division of Molecular Neurobiology, Rudolf Magnus Institute, University of Utrecht, The Netherlands.
Nielander
H B
HB
Vos
J P
JP
Lopes da Silva
S
S
Verhaagen
J
J
Oestreicher
A B
AB
Schrama
L H
LH
Schotman
P
P
Gispen
W H
WH
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology / Q000031:analogs & derivatives; D000818:Animals; D005260:Female; D019922:GAP-43 Protein; D005727:Ganglia, Spinal / Q000378:metabolism*; D006133:Growth Substances / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009043:Motor Activity / Q000502:physiology; D009409:Nerve Crush; D009416:Nerve Regeneration; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012584:Sciatic Nerve / Q000378:metabolism*; D012677:Sensation; D013979:Tibial Nerve / Q000502:physiology; D013997:Time Factors
D019922:GAP-43 Protein; D006133:Growth Substances; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D012333:RNA, Messenger; C013765:Org 2766; D000324:Adrenocorticotropic Hormone