Ultrastructural co-localization of calmodulin and B-50/growth-associated protein-43 at the plasma membrane of proximal unmyelinated axon shafts studied in the model of the regenerating rat sciatic nerve
| Autor: | A.J. Verkleij, W.H. Gispen, Paul Verkade, A.B. Oestreicher, L.H. Schrama |
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| Rok vydání: | 1997 |
| Předmět: |
Male
Nervous system Calmodulin Unmyelinated nerve fiber Nerve Tissue Proteins GAP-43 Protein medicine Animals Rats Wistar Axon Gap-43 protein Membrane Glycoproteins biology General Neuroscience Cell Membrane Immunohistochemistry Sciatic Nerve Molecular biology Axons Axolemma Nerve Regeneration Rats Cell biology Disease Models Animal Microscopy Electron medicine.anatomical_structure nervous system Axoplasm biology.protein Sciatic nerve |
| Zdroj: | Neuroscience. 79:1207-1218 |
| ISSN: | 0306-4522 |
| DOI: | 10.1016/s0306-4522(97)00041-9 |
| Popis: | Calmodulin and de-phosphorylated B-50/growth-associated protein-43 (GAP-43) have been shown to bind in vitro in a molecular complex, but evidence for an in situ association in the nervous system does not exist. Previously, we have reported that, in the model of the regenerating rat sciatic nerve, the B-50/GAP-43 immunoreactivity is increased and concentrated at the axolemma of unmyelinated axons located proximal to the site of injury and axon outgrowth. To explore a putative function of B-50/GAP-43, namely, the capacity of binding calmodulin to the plasma membrane, we examined the ultrastructural distribution of calmodulin in the proximal unmyelinated axon shafts of this model, using double immunolabelling and detection by fluorescent or gold probes conjugated to second antibodies. Immunofluorescence showed that seven days post-sciatic nerve crush the calmodulin immunoreactivity, similar to B-50/GAP-43 immunoreactivity, was intense in unmyelinated axon shafts located proximal to the site of injury of the regenerating nerve. Ultrastructurally, calmodulin was located at the axolemma of these regenerating unmyelinated axon shafts and inside the axoplasm, where it was associated with vesicles and microtubules. The plasma membrane labelling (approximately 69%) was significantly higher than the axoplasmic labelling. Over 60% of the plasma membrane-associated calmodulin co-localized with B-50/GAP-43 in a non-random distribution. Since normally calmodulin is largely present in the cytoplasm, these data suggest that calmodulin has been concentrated at the plasma membrane of unmyelinated axons, most probably by B-50/GAP-43. If the concentrating effect is due to B-50/GAP-43, then there is a possibility that these proteins may be present as a molecular complex in situ. The physiological significance could be that this association regulates the local availability of both B-50/GAP-43 and calmodulin for other interactions. |
| Databáze: | OpenAIRE |
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