Nitrogen metabolism profiling reveals cell state-specific pyrimidine synthesis pathway choice

Area of Science:

• Metabolic pathways
• Cellular metabolism
• Biochemistry

Background:

• Current stable isotope tracing methods are limited to a few metabolites, hindering a holistic view of cellular nitrogen metabolism.
• Cells utilize numerous nutrients for nitrogen metabolic pathways, necessitating advanced tracing techniques for comprehensive analysis.

Purpose of the Study:

• To develop a novel platform for simultaneous tracing of 30 nitrogen isotope-labeled metabolites.
• To investigate system-level nitrogen metabolism and its regulation in different cell states.

Main Methods:

• Development of a multi-metabolite nitrogen isotope tracing platform.
• Analysis of nitrogen metabolism in primitive versus differentiated cells, including primary tissues and tumor xenografts.
• Investigation of the role of Ser1900 phosphorylation of CAD in regulating pyrimidine synthesis.

Main Results:

• The new platform successfully traced 30 nitrogen metabolites simultaneously.
• Differentiated cells predominantly utilize pyrimidine salvage pathways over de novo synthesis, despite expressing de novo enzymes.
• Ser1900 phosphorylation of CAD was identified as a key regulatory mechanism for cell state-specific pyrimidine synthesis pathway choice.

Conclusions:

• A novel method for comprehensive nitrogen metabolism profiling has been established.
• Cell state significantly influences the choice between de novo and salvage pyrimidine synthesis pathways.
• Phosphorylation of the CAD enzyme is a critical determinant of this metabolic pathway selection.