The polysialylated neural cell adhesion molecule reaches cell surfaces of hypothalamic neurons and astrocytes via the constitutive pathway
| Autor: | Dionysia T. Theodosis, B. Dupouy, Renée Bonhomme, Dominique A. Poulain, Karin Pierre |
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| Rok vydání: | 2001 |
| Předmět: |
Male
Hypothalamus Fluorescent Antibody Technique Neural Cell Adhesion Molecule L1 Biology Culture Techniques medicine Animals Premovement neuronal activity Rats Wistar Cell adhesion Neural Cell Adhesion Molecules Neurons Microscopy Confocal Cell adhesion molecule General Neuroscience Biological Transport Depolarization Rats Cell biology medicine.anatomical_structure Animals Newborn nervous system Astrocytes Sialic Acids Neuroglia Female Neural cell adhesion molecule Neurosecretion Neuroscience Astrocyte |
| Zdroj: | Neuroscience. 103:133-142 |
| ISSN: | 0306-4522 |
| Popis: | Understanding how neurons and glia sort and deliver cell adhesion molecules to their cell surface should provide important clues as to how such molecules participate in dynamic neuronal functions in the developing and adult brain. The present study examines translocation of polysialylated neural cell adhesion molecule (PSA-NCAM), a negative regulator of cell adhesion, in cells of the rat hypothalamo-neurohypophysial system in which it is expressed throughout life and which undergo morphological remodelling in response to stimulation. PSA-NCAM expression in this system does not vary markedly in relation to different conditions of regulated neurosecretion, suggesting that the glycoprotein reaches cell surfaces via the constitutive pathway. To study this more directly, we here used immunofluorescence for PSA on NCAM in live, unpermeabilized cells to monitor PSA-NCAM surface expression in organotypic slice cultures from postnatal rat hypothalami. Subsequent immunolabelling for oxytocin confirmed that the cultures included magnocellular oxytocinergic neurons displaying many properties of adult neurosecretory neurons in situ . In the cultures, immunoreaction for PSA-NCAM was visible on the surface of oxytocinergic and non-oxytocinergic axons. This reaction disappeared after exposure of the cultures to endoneuraminidase, an enzyme which specifically cleaves α-2-8-linked PSA from NCAM. PSA-NCAM reappeared on axonal surfaces 4 h after enzyme washout. Such reexpression was visibly not affected by neuronal activity inhibition (blockade of Ca 2+ channels with Mn 2+ , of Na + channels with tetrodotoxin, or of glutamate receptors with 6-cyano-7-nitroquinoxaline-2,3-dione or d -2-amino-5-phosphonopentanoic acid) or facilitation (K + depolarization or GABA-A receptor blockade with bicuculline). In contrast, PSA-NCAM surface translocation was inhibited reversibly by cooling the cultures at 20°C, a procedure which blocks constitutive secretion and which resulted in accumulation of PSA-NCAM in the cytoplasm of oxytocinergic and non-oxytocinergic neurons. This treatment also revealed PSA-NCAM in the cytoplasm of underlying astrocytes. Our observations provide direct evidence that PSA-NCAM reaches the cell surface of hypothalamic neurons and astrocytes via the constitutive pathway, independently of Ca 2+ entry and enhanced neuronal activity. Thus, PSA-NCAM in the hypothalamo-neurohypophysial system would be continuously available to permit its cells to undergo remodelling whenever the proper stimulus intervenes. |
| Databáze: | OpenAIRE |
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