Synaptic junctional glycoconjugates from chick brain. Glycoprotein identification and carbohydrate composition

Area of Science:

• Neuroscience
• Biochemistry
• Cell Biology

Background:

• Synaptic junctions are critical for neuronal communication.
• Understanding the molecular composition of synaptic junctions, particularly glycoproteins, is essential for elucidating their function.

Purpose of the Study:

• To identify and characterize glycoproteins within subsynaptic membrane fractions, focusing on synaptic junctions.
• To determine the carbohydrate composition of glycoproteins in various subcellular fractions.

Main Methods:

• Differential sedimentation and density gradient centrifugation to isolate subcellular fractions.
• Triton X-100 treatment to obtain subsynaptic membrane fractions, including synaptic junctions.
• SDS-polyacrylamide gel electrophoresis and radioiodinated concanavalin A staining to identify glycoproteins.
• Gas-liquid chromatography to quantitate carbohydrate content of glycoproteins.

Main Results:

• Two lectin-binding glycoproteins were identified in the synaptic junction fraction.
• Synaptic junctions had the lowest overall glycoprotein sugar concentration.
• Synaptic junctions exhibited a high proportion of mannose and low sialic acid, with low relative amounts of galactose and N-acetylglucosamine.

Conclusions:

• Synaptic junctions are characterized by a limited number of high-molecular-weight glycoproteins.
• The oligosaccharide chains in the synaptic cleft are predominantly neutral and mannose-rich.
• These findings provide insights into the specific glycoprofile of synaptic junctions.