A fast, simple and sensitive method for the detection and quantification of detergent-resistant membranes

Area of Science:

• Cell Biology
• Biochemistry
• Immunology

Background:

• Molecular activation clusters form in T cell membranes during T cell receptor aggregation.
• These clusters, known as lipid microdomains or detergent-resistant membranes (DRM), are enriched in cholesterol, sphingomyelin, and gangliosides.
• Distinct subgroups of lipid microdomains exist, containing different signaling molecules, and are typically isolated using sucrose density centrifugation.

Purpose of the Study:

• To develop and validate a novel, simple, and non-radioactive method for quantifying ganglioside GM1 associated with DRM.
• To utilize this method for analyzing DRM composition in T cells.

Main Methods:

• A new assay employing a cholera toxin B subunit-horseradish peroxidase (CTB-HRP) conjugate and ABTS substrate was developed for DRM detection.
• Quantification was performed using absorbance readings at 405 nm in a microtiter plate format.
• The method's linearity and detection limit were established using varying peroxidase activity and CTB concentrations.

Main Results:

• The developed assay demonstrated linearity over a wide range of peroxidase activity and a low limit of detection (approx. 10 ng CTB per fraction).
• Application to Jurkat T cells revealed DRM at the 5%/30% sucrose interface.
• Fractions 4-6 showed high GM1 content, confirmed by CTB-HRP binding, and contained proteins including LAT and Lck kinases.

Conclusions:

• A rapid, easy, and non-radioactive method for quantifying GM1 in DRM has been successfully established.
• This method facilitates the analysis of DRM-resident proteins.
• DRM, enriched in GM1, LAT, and Lck, are present at the sucrose gradient interface in Jurkat T cells.