Format

Send to

Choose Destination
J Membr Biol. 2016 Aug;249(4):539-49. doi: 10.1007/s00232-016-9896-z. Epub 2016 Apr 26.

Heterogeneous Inhibition in Macroscopic Current Responses of Four Nicotinic Acetylcholine Receptor Subtypes by Cholesterol Enrichment.

Author information

1
Department of Biology, University of Puerto Rico, Río Piedras Campus, PO Box 23360, San Juan, PR, 00931, USA. cbaezpagan@gmail.com.
2
Molecular Sciences Research Center, University of Puerto Rico, San Juan, PR, USA. cbaezpagan@gmail.com.
3
Department of Physical Sciences, University of Puerto Rico, Río Piedras Campus, PO Box 23323, San Juan, PR, 00931, USA. cbaezpagan@gmail.com.
4
School of Pharmacy, Medical Sciences Campus, University of Puerto Rico, San Juan, PR, USA.
5
Department of Physical Sciences, University of Puerto Rico, Río Piedras Campus, PO Box 23323, San Juan, PR, 00931, USA.
6
Department of Biology, University of Puerto Rico, Río Piedras Campus, PO Box 23360, San Juan, PR, 00931, USA.
7
Department of Biology, University of Puerto Rico, Río Piedras Campus, PO Box 23360, San Juan, PR, 00931, USA. jlasalde@gmail.com.
8
Molecular Sciences Research Center, University of Puerto Rico, San Juan, PR, USA. jlasalde@gmail.com.

Abstract

The nicotinic acetylcholine receptor (nAChR), located in the cell membranes of neurons and muscle cells, mediates the transmission of nerve impulses across cholinergic synapses. In addition, the nAChR is also found in the electric organs of electric rays (e.g., the genus Torpedo). Cholesterol, which is a key lipid for maintaining the correct functionality of membrane proteins, has been found to alter the nAChR function. We were thus interested to probe the changes in the functionality of different nAChRs expressed in a model membrane with modified cholesterol to phospholipid ratios (C/P). In this study, we examined the effect of increasing the C/P ratio in Xenopus laevis oocytes expressing the neuronal α7, α4β2, muscle-type, and Torpedo californica nAChRs in their macroscopic current responses. Using the two-electrode voltage clamp technique, it was found that the neuronal α7 and Torpedo nAChRs are significantly more sensitive to small increases in C/P than the muscle-type nAChR. The peak current versus C/P profiles during enrichment display different behaviors; α7 and Torpedo nAChRs display a hyperbolic decay with two clear components, whereas muscle-type and α4β2 nAChRs display simple monophasic decays with different slopes. This study clearly illustrates that a physiologically relevant increase in membrane cholesterol concentration produces a remarkable reduction in the macroscopic current responses of the neuronal α7 and Torpedo nAChRs functionality, whereas the muscle nAChR appears to be the most resistant to cholesterol inhibition among all four nAChR subtypes. Overall, the present study demonstrates differential profiles for cholesterol inhibition among the different types of nAChR to physiological cholesterol increments in the plasmatic membrane. This is the first study to report a cross-correlation analysis of cholesterol sensitivity among different nAChR subtypes in a model membrane.

KEYWORDS:

Cholesterol; Ion channels; Membrane proteins; Nicotinic acetylcholine receptor; Regulation

PMID:
27116687
PMCID:
PMC4945412
DOI:
10.1007/s00232-016-9896-z
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Springer Icon for PubMed Central
Loading ...
Support Center