Designing the lipid raft marker protein for synaptic vesicles

Lipid rafts are cholesterol-enriched microdomains and implicated in many essential physiological activities such as the neurotransmitter release. Many studies have been carried out on the function of rafts in the plasma membranes, whereas little is known about the information of such microdomains in subcellular compartments especially synaptic vesicles (SVs). In the well-studied plasma membranes, several proteins have been recognized as raft markers, which are used to label or trace rafts. But the raft marker protein on SVs has not been identified yet. Although some SV proteins, including VAMP and CPE, have been found in raft fractions, they cannot be used as markers due to their low abundance in rafts. In this work, we designed several chimera proteins and tested their characteristics for using as SV raft makers. First, we detected whether they located in SVs, and then the chimeras exhibiting the better localization in SVs were further examined for their enrichment in raft using detergent treatment and gradient density floatation analysis. Our results indicate that one of the chimeric proteins is primarily located in SVs and distributed in raft microdomains, which strongly suggests that it could be served as a raft marker for SVs.