Title

Bilayer thickness modulates the conductance of the BK channel in model membranes

UMMS Affiliation

Department of Neurobiology; Treistman Lab; Graduate School of Biomedical Sciences, Neuroscience Program

Date

6-11-2004

Document Type

Article

Subjects

Cells, Cultured; Humans; *Image Processing, Computer-Assisted; Ion Channel Gating; Large-Conductance Calcium-Activated Potassium Channels; Lipid Bilayers; Lipids; Microscopy, Atomic Force; Potassium Channels, Calcium-Activated

Disciplines

Biophysics | Neuroscience and Neurobiology

Abstract

The conductance of the BK channel was evaluated in reconstituted bilayers made of POPE/POPS (3.3:1), or POPE/POPS with an added 20% of either SPM (3.3:1:1), CER (3.3:1:1), or CHL (3.3:1:1). The presence of SPM, which is known to increase bilayer thickness, significantly reduced the conductance of the BK channel. To directly test the role of membrane thickness, the conductance of the BK channel was measured in bilayers formed from PCs with acyl chains of increasing length (C14:1-C24:1), all in the absence of SPM. Slope conductance was maximal at a chain length of (C18:1) and much reduced for both thinner (C14:1) and thicker (C24:1) bilayers, indicating that membrane thickness alone can modify slope conductance. Further, in a simplified binary mixture of DOPE/SPM that forms a confined, phase-separated bilayer, the measured conductance of BK channels shows a clear bimodal distribution. In contrast, the addition of CER, which has an acyl chain structure similar to SPM but without its bulky polar head group to POPE/POPS, was without effect, as was the addition of CHL. The surface structure of membranes made from these same lipid mixtures was examined with AFM. Incorporation of both SPM and CER resulted in the formation of microdomains in POPE/POPS monolayers, but only SPM promoted a substantial increase in the amount of the high phase observed for the corresponding bilayers. The addition of CHL to POPE/POPS eliminated the phase separation observed in the POPE/POPS bilayer. The decrease in channel conductance observed with the incorporation of SPM into POPE/POPS membranes was, therefore, attributed to larger SPM-rich domains that appear thicker than the neighboring bilayer.

Rights and Permissions

Citation: Biophys J. 2004 Jun;86(6):3620-33. Link to article on publisher's site

DOI of Published Version

10.1529/biophysj.103.029678

Comments

Co-author Paula L. Feinberg-Zadek is a student in the Neuroscience program in the Graduate School of Biomedical Sciences (GSBS) at UMass Medical School.

Related Resources

Link to article in PubMed

Journal Title

Biophysical journal

PubMed ID

15189859