The influence of cholesterol on synaptic fluidity and dopamine uptake.
The present study examined how the synaptic cholesterol/phospholipid ratio influences membrane fluidity and a transmembrane process of the dopaminergic system, dopamine uptake. Fluorescence polarization of DPH was used as a measure of membrane fluidity. The cholesterol content of synaptosomal and synaptic plasma membranes was altered using a lipid transfer protein. The results of the present study demonstrate that the transmembrane process of dopamine uptake may be inhibited by an elevated synaptic cholesterol/phospholipid ratio, which correlates with increased fluorescence polarization. Specifically, a 10-30% increase in the cholesterol/phospholipid ratio resulted in an approximately 20% increase in fluorescence polarization, a 3- to 6-fold increase in Km, a 4-fold increase in Vmax, and a marked decrease in the Vmax/Km (the first order rate constant for dopamine uptake at low substrate concentrations).
Maguire
P A
PA
Department of Biochemistry and Biophysics, Loyola University Stritch School of Medicine, Maywood 60153.
Druse
M J
MJ
D000818:Animals; D002352:Carrier Proteins / Q000494:pharmacology*; D002784:Cholesterol / Q000378:metabolism / Q000502:physiology*; D004298:Dopamine / Q000493:pharmacokinetics*; D066298:In Vitro Techniques; D008081:Liposomes; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism / Q000502:physiology*; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013569:Synapses / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D002352:Carrier Proteins; D008081:Liposomes; D008563:Membrane Lipids; D010743:Phospholipids; C030363:lipid transfer protein; D002784:Cholesterol; D004298:Dopamine