Ultrastructural localization of B-50/growth-associated protein-43 to anterogradely transported synaptophysin-positive and calcitonin gene-related peptide-negative vesicles in the regenerating rat sciatic nerve.
The growth-associated protein-43/B-50 (B-50/GAP-43) is conveyed from the neuronal soma into the axon by fast axonal transport and moved to the nerve terminal. To visualize and determine the type of vesicles by which B-50/GAP-43 is anterogradely transported in the regenerating rat sciatic nerve, we have investigated Lowicryl HM20 embedded nerve pieces dissected from the proximal side of a collection ligature. Ultrastructurally, numerous vesicular profiles of various sizes, tubules and mitochondria were seen to accumulate proximal to the collection ligature. Both, in unmyelinated and myelinated axons, B-50/GAP-43 immunoreactivity was associated with vesicular profiles which had a diameter of 50 nm. A fraction of the B-50/GAP-43 label co-localized with the small vesicle marker synaptophysin. Co-localization of B-50/GAP-43 was not detected with the large dense-core vesicle marker calcitonin gene-related peptide. These results indicate that, in rat sciatic nerve axons, B-50/GAP-43 is anterogradely transported in small 50 nm vesicles of the constitutive pathway. These transport vesicles were distinguished in two types. We suggest that one type carrying, both, B-50 GAP-43 and synaptophysin has as destination the nerve terminal, whereas the second type, which only contains B-50/GAP-43 and no synaptophysin, may be primarily targeted to the axolemma for local membrane fusion.
Verkade
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Rudolf Magnus Institute for Neurosciences, University of Utrecht, The Netherlands.
Verkleij
A J
AJ
Annaert
W G
WG
Gispen
W H
WH
Oestreicher
A B
AB
D000818:Animals; D001370:Axonal Transport / Q000502:physiology; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D019922:GAP-43 Protein; D007150:Immunohistochemistry; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008854:Microscopy, Electron; D009416:Nerve Regeneration / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016613:Plastic Embedding; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve / Q000378:metabolism* / Q000648:ultrastructure*; D013572:Synaptic Vesicles / Q000378:metabolism / Q000648:ultrastructure; D016708:Synaptophysin / Q000378:metabolism*
D019922:GAP-43 Protein; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D016708:Synaptophysin; D015740:Calcitonin Gene-Related Peptide