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Hyaluronan and hyaluronectin in the nervous system
B Delpech1, A Delpech, G Brückner
1Laboratoire d'Oncologie moléculaire, Centre Henri-Becquerel, Rouen, France.
Ciba Foundation Symposium
|January 1, 1989
Summary
Hyaluronan (HA) and hyaluronectin (HN) are key molecules in the central nervous system. This study reveals their complex interactions and developmental changes, suggesting a role in neural function.
Area of Science:
- Neuroscience
- Biochemistry
- Molecular Biology
Background:
- Hyaluronan (HA) is a glycosaminoglycan present in extracellular matrices.
- Hyaluronectin (HN) is a glycoprotein that binds HA.
- The roles of HA and HN in the nervous system are not fully understood.
Purpose of the Study:
- To investigate the presence and interactions of HA and HN in nervous tissue.
- To characterize the binding properties of HN to HA.
- To explore the developmental changes and localization of HA and HN in the brain.
Main Methods:
- Extraction of HA and HN from nervous system tissues.
- Protease digestion to enhance quantitative analysis.
- Indirect enzyme immunological assay for quantification.
- In vitro binding assays using HA and its oligosaccharides.
- Immunohistochemistry and electron microscopy for localization.
- Analysis of HA and HN concentrations during development.
Main Results:
- Extraction of HA was enhanced by protease digestion and favored at neutral/alkaline pH.
- HA in brain tissue at neutral pH is bound to HN, a glycoprotein mainly expressed in the central nervous system.
- HN (68 kDa) binds HA and HA-derived oligosaccharides with high affinity (Kd ~10^-8 M).
- HA-HN complexes are found in human cerebrospinal fluid.
- HA concentration decreases from fetus to adult, while HN concentration increases.
- In rats, HA levels drop sharply around birth.
- During embryonic development, HA is an extracellular component in cerebral cortex migration and proliferation areas.
- In adult rats, HA is found at nodes of Ranvier and perineuronal structures.
- HN localizes to similar areas but is associated with specific neurons.
- In the cerebellum, HA-HN is concentrated in grey nuclei, granular layer, and around Purkinje cells.
- Electron microscopy shows HN in the cytoplasm and plasma membrane of perisynaptic glial cell processes.
Conclusions:
- HA and HN form complexes in the central nervous system, with HN binding HA and HA-derived oligosaccharides.
- Developmental changes in HA and HN concentrations suggest dynamic roles in neural development and maturation.
- The localization of HA-HN complexes points to involvement in specific neural structures and cell types.
- A proposed hypothesis suggests HA-HN involvement in neural GABAergic transmission.