Immunochemical characterization of brain synaptic membrane glutamate-binding proteins

Area of Science:

• Neuroscience and Neurochemistry
• Molecular Biology and Immunology

Background:

• Two glutamate-binding proteins (71 and 63 kDa) were previously identified in synaptic plasma membranes.
• These proteins are hypothesized to be involved in glutamate neurotransmission within the brain.

Purpose of the Study:

• To generate and characterize polyclonal antibodies against the 71 and 63 kDa glutamate-binding proteins.
• To investigate the role of these proteins in glutamate neurotransmission using immunological techniques.

Main Methods:

• Production of polyclonal antibodies against purified glutamate-binding proteins.
• Western blotting, enzyme-linked immunosorbent assays (ELISAs), and immunoaffinity chromatography.
• Immunohistochemistry with gold particle labeling and electron microscopy on brain tissue.

Main Results:

• Antibodies specifically recognized both 71 and 63 kDa proteins in denatured and native forms.
• Immunoextraction of these proteins reduced L-[3H]glutamate binding activity by approximately 60%.
• Immunohistochemistry localized the proteins to postsynaptic membranes and neuronal structures in glutamate-rich brain regions.

Conclusions:

• The two glutamate-binding proteins are immunologically related but exhibit differential reactivity.
• These proteins are major components of synaptic glutamate-binding sites.
• The findings strongly support a critical role for these glutamate-binding proteins in brain glutamate neurotransmission.