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Smooth muscle raft-like membranes.
Carl B Baron1, Ronald F Coburn
1Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA. cbaron@mail.med.upenn.edu
Journal of Lipid Research
|October 18, 2003
Summary
Researchers developed a new method to isolate liquid-ordered membranes from smooth muscle tissue. This technique uses octyl glucoside (OG) to extract these specialized cell membranes, aiding in their study.
Area of Science:
- Biochemistry
- Cell Biology
- Membrane Biophysics
Background:
- Plasma membranes contain specialized microdomains, including liquid-ordered (LO) membranes, crucial for cellular functions.
- Triton X-100 is commonly used to isolate detergent-resistant membranes, often presumed to be LO.
- Porcine trachealis smooth muscle provides a relevant model for studying plasma membrane composition.
Purpose of the Study:
- To develop and validate a method for extracting LO membranes from porcine trachealis smooth muscle.
- To characterize the lipid and protein composition of membranes extracted using octyl glucoside (OG).
- To compare the extraction efficiency and characteristics of OG with Triton X-100.
Main Methods:
- Homogenization of porcine trachealis smooth muscle particulate fraction with cold 0.5% Triton X-100.
- Centrifugation to obtain Triton X-100-resistant pellet enriched in sphingomyelin (SM) and cholesterol.
- Extraction of membranes from the pellet using 35 mM octyl glucoside (OG) and subsequent analysis.
Main Results:
- OG extracted 75% of membranes from the Triton X-100-resistant pellet, characterized by low buoyant density.
- These OG-extracted membranes showed a lipid composition (22% SM, 60% cholesterol) consistent with LO membranes.
- Co-isolation with 5'-nucleotidase and caveolin-1 further supports the LO nature of OG-extracted membranes.
- OG extraction yielded membranes with characteristics differing from Triton X-100, indicating non-selective extraction of LO membranes.
Conclusions:
- Octyl glucoside (OG) effectively extracts a significant portion of membranes from Triton X-100-resistant fractions of porcine trachealis smooth muscle.
- The extracted membranes exhibit properties indicative of liquid-ordered (LO) domains, supported by lipid and protein analysis.
- Low buoyant density is not exclusively characteristic of LO membranes, challenging previous assumptions based on Triton X-100 extraction methods.