Brain contains two forms of synaptic vesicle protein 2

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Synaptic vesicle protein 2 (SV2) shares homology with proton cotransporters and glucose transporters.
• This homology suggests SV2 may be involved in neurotransmitter uptake via a proton gradient.
• The existence of a gene family for SV2 proteins was hypothesized.

Purpose of the Study:

• To identify potential new members of the SV2 gene family.
• To characterize the newly identified SV2B protein and its expression patterns.
• To determine if SV2 proteins constitute a gene family.

Main Methods:

• Molecular cloning of SV2 cDNA from rat brain.
• Screening for homologous cDNAs using the SV2 clone.
• Characterization of identified clones, including sequencing and protein expression in COS cells.
• Immunological detection using a monoclonal antibody defining SV2.
• Analysis of SV2A and SV2B expression in different brain regions.

Main Results:

• Identification and characterization of SV2B, a novel protein 65% identical and 78% similar to SV2 (SV2A).
• SV2B is recognized by the SV2-defining monoclonal antibody.
• Expression of SV2B in COS cells shows reticular labeling, indicating localization to intracellular membranes.
• SV2B expression is restricted to neural tissue, with highest levels in the cortex and hippocampus.
• SV2A shows highest expression in subcortical regions.

Conclusions:

• Synaptic vesicle protein 2 (SV2) and SV2B represent a small gene family of synaptic vesicle proteins.
• Both SV2A and SV2B are localized to intracellular membranes within neural tissue.
• Differential expression patterns of SV2A and SV2B suggest distinct roles within the brain.