Low levels of methyl β‐cyclodextrin disrupt GluA1‐dependent synaptic potentiation but not synaptic depression

Abstract

Abstract Methyl‐β‐cyclodextrin (MβCD) is a reagent that depletes cholesterol and disrupts lipid rafts, a type of cholesterol‐enriched cell membrane microdomain. Lipid rafts are essential for neuronal functions such as synaptic transmission and plasticity, which are sensitive to even low doses of MβCD. However, how MβCD changes synaptic function, such as N ‐methyl‐ d ‐aspartate receptor (NMDA‐R) activity, remains unclear. We monitored changes in synaptic transmission and plasticity after disrupting lipid rafts with MβCD. At low concentrations (0.5 mg/mL), MβCD decreased basal synaptic transmission and miniature excitatory post‐synaptic current without changing NMDA‐R‐mediated synaptic transmission and the paired‐pulse facilitation ratio. Interestingly, low doses of MβCD failed to deplete cholesterol or affect α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptor (AMPA‐R) and NMDA‐R levels, while clearly reducing GluA1 levels selectively in the synaptosomal fraction. Low doses of MβCD decreased the inhibitory effects of NASPM, an inhibitor for GluA2‐lacking AMPA‐R. MβCD successfully decreased NMDA‐R‐mediated long‐term potentiation but did not affect the formation of either NMDA‐R‐mediated or group I metabotropic glutamate receptor‐dependent long‐term depression. MβCD inhibited de‐depression without affecting de‐potentiation. These results suggest that MβCD regulates GluA1‐dependent synaptic potentiation but not synaptic depression in a cholesterol‐independent manner. image MβCD at low concentrations (0.5 mg/mL) did not deplete cholesterol or affect AMPA‐R and NMDA‐R levels in the lipid raft fraction, while clearly reducing GluA1 levels in the synaptosomal fraction. Interestingly, MβCD decreased LTP but did not affect LTD induction. These results suggest that MβCD regulates GluA1‐dependent synaptic potentiation but not synaptic depression in a lipid raft‐independent manner. AMPA‐R, α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptor; GluA1, AMPAR subunit glutamate receptor 1; LTD, long‐term depression; LTP, long‐term potentiation; MβCD, methyl β–cyclodextrin; NMDA‐R, N ‐methyl‐ d ‐aspartate receptor.