Low levels of methyl beta-cyclodextrin disrupt GluA1-dependent synaptic potentiation but not synaptic depression

摘要

Methyl--cyclodextrin (MCD) 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 MCD. However, how MCD 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 MCD. At low concentrations (0.5mg/mL), MCD 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 dosesof MCD failed to deplete cholesterol or affect -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 MCD decreased the inhibitory effects of NASPM, an inhibitor for GluA2-lacking AMPA-R. MCD 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. MCD inhibited de-depression without affecting de-potentiation. These results suggest that MCD regulates GluA1-dependent synaptic potentiation but not synaptic depression in a cholesterol-independent manner.