The cholesterol-complexing agent digitonin modulates ligand binding of the bovine hippocampal serotonin 1A receptor.
The serotonin(1A) (5-HT(1A)) receptor is an important member of the superfamily of seven transmembrane domain G-protein-coupled receptors. We have examined the modulatory role of cholesterol on the ligand binding of the bovine hippocampal 5-HT(1A) receptor by cholesterol complexation in native membranes using digitonin. Complexation of cholesterol from bovine hippocampal membranes using digitonin results in a concentration-dependent reduction in specific binding of the agonist 8-OH-DPAT and antagonist p-MPPF to 5-HT(1A) receptors. The corresponding changes in membrane order were monitored by analysis of fluorescence polarization data of the membrane depth-specific probes, DPH and TMA-DPH. Taken together, our results point out the important role of membrane cholesterol in maintaining the function of the 5-HT(1A) receptor. An important aspect of these results is that non-availability of free cholesterol in the membrane due to complexation with digitonin rather than physical depletion is sufficient to significantly reduce the 5-HT(1A) receptor function. These results provide a comprehensive understanding of the effects of the sterol-complexing agent digitonin in particular, and the role of membrane cholesterol in general, on the 5-HT(1A) receptor function.
Paila
Yamuna Devi
YD
Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
Pucadyil
Thomas J
TJ
Chattopadhyay
Amitabha
A
D000818:Animals; D002417:Cattle; D002784:Cholesterol / Q000502:physiology*; D004072:Digitonin / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D008024:Ligands; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D044282:Receptor, Serotonin, 5-HT1A / Q000187:drug effects* / Q000378:metabolism
D008024:Ligands; D044282:Receptor, Serotonin, 5-HT1A; D002784:Cholesterol; D004072:Digitonin