Brain Glutamate Transporter Proteins Form Homomultimers

摘要: Removal of excitatory amino acids from the extracellular fluid is essential for synaptic transmission and avoiding excitotoxicity. The removal accomplished by glutamate transporters located in plasma membranes both neurons astroglia. uptake system consists several different transporter proteins that are carefully regulated, indicating more refined functions than simple transmitter inactivation. Here we show chemical cross-linking, followed electrophoresis immunoblotting, three rat brain (GLAST, GLT EAAC) form homomultimers. multimers exist not only intact but also after solubilization reconstitution liposomes. Increasing cross-linker concentration increased immunoreactivity bands corresponding to trimers at expense dimer monomer bands. However, immunoreactivities did disappear, a mixture dimers trimers. GLAST do complex with each other, as demonstrated double labeling post-embedding electron microscopic immunocytochemistry, they co-exist side same astrocytic cell membranes. oligomers held together noncovalently vivo. In vitro, oxidation induces formation covalent bonds (presumably -S-S-) between subunits leading appearance oligomer on SDS-polyacrylamide gel electrophoresis. Immunoprecipitation experiments suggest quantitatively dominant brain. Radiation inactivation analysis gives molecular target size functional oligomeric structure. We postulate operate homomultimeric complexes.