A simple, highly sensitive, and facile method to quantify ceramide at the plasma membrane.

Area of Science:

• Lipid Biology
• Cellular Signaling
• Biochemistry

Background:

• Ceramide's biological roles are often assessed via total cellular levels, potentially missing organelle-specific functions.
• Plasma membrane ceramide, though critical for cell signaling, is difficult to quantify due to low abundance and lack of specific methods.

Purpose of the Study:

• To develop and validate a method for quantifying ceramide specifically within the plasma membrane.
• To enable the study of compartmentalized ceramide functions in cellular processes.

Main Methods:

• Enzymatic hydrolysis of plasma membrane ceramide to sphingosine using bacterial neutral ceramidase.
• Chemical fixation to halt endogenous sphingolipid metabolism, ensuring accurate sphingosine measurement.
• Quantification of generated sphingosine via a 1:1 stoichiometric conversion from plasma membrane ceramide.

Main Results:

• A novel, efficient protocol for measuring plasma membrane ceramide mass was established.
• The method demonstrated stability, with chemical fixation preserving plasma membrane integrity.
• The approach was successfully applied to study doxorubicin's effects, revealing distinct ceramide pools.

Conclusions:

• This study presents the first method to quantify plasma membrane ceramide.
• The technique opens new avenues for investigating sphingolipid compartmentalization and function.
• It facilitates a deeper understanding of localized ceramide roles in cellular signaling and drug response.